Dynojet needles
10-07-2007, 04:34 AM
#1
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
Dynojet needles
Hi fellas,
I'm new to the forum. I have recently purchased a VTR firestorm the superhawk equivalent here in Aus.
The bike has straight through black max pipes and come with standard jetting. It ran quite well but after reading the forum I decided to try and improve bottom end throttle response and rather than shim the needles I opted for the dynojet kit.
I have a fair bit of experience with jetting carbs including both 2 and 4 stroke aswell as efi tuning.
So I decided to pull the carbs and do some fiddling. Upon removing I noticed there were no restrictors on the manifold, so that saved a bit of time. I pulled out the old needles and began to compare the stockers with dynojet needles. They appear very different indeed. I installed the needles on the 5th clip with 180/185 mains, 45 slow jet mix screw 2.5 turns out . I also removed the pollution gear and removed the airbox baffle.
After syncing the carbs I took it for a ride. Once warmed up it stumbled a little on the transition from pilot to needle circuit(about 1/8-1/4 throttle). Immediately I figured it was a little rich considering I just replaced needles to DJ on the 5th clip. Tank back off went to 4th clip, checked carb sync and this time the problem was worse!
Checked the plugs they were both nice and white!(way to lean) This time I measured needle length and diameters with micrometers. With the clip in groove 5 both the stock and DJ needles are similiar length. But the pilot area of the stock needle is much richer due to the sharper angle and greater taper. The DJ needle is leaner in the pilot area but due to its slight taper becomes much richer in the middle than the stock needle. So to make the DJ needle work I had to run it on the 6th clip. This way I am ensuring a richer transition from pilot to needle circuits. I end up with a richer middle but I need it anyway. The big Twin breaths heavy and has a high manifold vacuum with short duration camshafts so it needs plenty of fuel to get good response. The big girl refused to rev under load on clip 4 and clip 6 is like a new bike. I still not have fitted K and N as of yet and if so I may have to shim more.
I must say no 2 vtr twin motors are the same and will require different jetting requirements. While I am impressed with the way my engine runs, and the design of the DJ needle. The needle position has me concerned. Especially from a company like DJ. I would have thought they would have designed the needle for a VTR with pipes to run nicely on the middle clip. A good starting point(like any engine) While here I am(and many other owners) putting the clip on the 6th groove.
Readers please be aware of this and be prepared to run the DJ needles on the richest setting!
Just some food for thought...
Cheers,
Joel
I'm new to the forum. I have recently purchased a VTR firestorm the superhawk equivalent here in Aus.
The bike has straight through black max pipes and come with standard jetting. It ran quite well but after reading the forum I decided to try and improve bottom end throttle response and rather than shim the needles I opted for the dynojet kit.
I have a fair bit of experience with jetting carbs including both 2 and 4 stroke aswell as efi tuning.
So I decided to pull the carbs and do some fiddling. Upon removing I noticed there were no restrictors on the manifold, so that saved a bit of time. I pulled out the old needles and began to compare the stockers with dynojet needles. They appear very different indeed. I installed the needles on the 5th clip with 180/185 mains, 45 slow jet mix screw 2.5 turns out . I also removed the pollution gear and removed the airbox baffle.
After syncing the carbs I took it for a ride. Once warmed up it stumbled a little on the transition from pilot to needle circuit(about 1/8-1/4 throttle). Immediately I figured it was a little rich considering I just replaced needles to DJ on the 5th clip. Tank back off went to 4th clip, checked carb sync and this time the problem was worse!
Checked the plugs they were both nice and white!(way to lean) This time I measured needle length and diameters with micrometers. With the clip in groove 5 both the stock and DJ needles are similiar length. But the pilot area of the stock needle is much richer due to the sharper angle and greater taper. The DJ needle is leaner in the pilot area but due to its slight taper becomes much richer in the middle than the stock needle. So to make the DJ needle work I had to run it on the 6th clip. This way I am ensuring a richer transition from pilot to needle circuits. I end up with a richer middle but I need it anyway. The big Twin breaths heavy and has a high manifold vacuum with short duration camshafts so it needs plenty of fuel to get good response. The big girl refused to rev under load on clip 4 and clip 6 is like a new bike. I still not have fitted K and N as of yet and if so I may have to shim more.
I must say no 2 vtr twin motors are the same and will require different jetting requirements. While I am impressed with the way my engine runs, and the design of the DJ needle. The needle position has me concerned. Especially from a company like DJ. I would have thought they would have designed the needle for a VTR with pipes to run nicely on the middle clip. A good starting point(like any engine) While here I am(and many other owners) putting the clip on the 6th groove.
Readers please be aware of this and be prepared to run the DJ needles on the richest setting!
Just some food for thought...
Cheers,
Joel
Last edited by hymey; 10-07-2007 at 04:41 AM. Reason: because
10-07-2007, 08:11 AM
#2
WERA #44
Superstock
Join Date: Jul 2007
Location: About 57 miles south of VIR
Posts: 265
Thanks
Nice of you to post your experience.
I am going to my friend's today with my project on the trailer and carb set up and sync are on the agenda. I have MIG slip ons, K&N air filter
I have armed myself with much of the posts like yours, a factory book, and a dynojet kit.
Many topics here have instructed me in the build of this bike and how to avoid the common glitches and mistakes.
Thanks to all of you! Rob
I am going to my friend's today with my project on the trailer and carb set up and sync are on the agenda. I have MIG slip ons, K&N air filter
I have armed myself with much of the posts like yours, a factory book, and a dynojet kit.
Many topics here have instructed me in the build of this bike and how to avoid the common glitches and mistakes.
Thanks to all of you! Rob
10-07-2007, 03:40 PM
#3
Seņor Miembro, Ay Caramba
SuperSport
Join Date: May 2006
Location: a little north of DC
Posts: 562
If you're really running straight pipes, I'd say your #45 is too lean (plus, your clip is in the 6th position). You should get ahold of a 48 or 50. Obviously your needle clip position will go down too. I'd start with that and see how close you can get.
10-07-2007, 04:21 PM
#4
Senior Member
SuperBike
Join Date: Jul 2005
Location: MN
Posts: 1,548
I haven't been that impressed with the dynojet kit and have messed with it for awhile on my bike through various mods. With just slipons I didn't notice any significant improvement except improve throttle response in midrange to WFO. Did you switch springs and drill the slides? They design their needles to work with that mod - it does seem to improve response but there was zero gain on a dyno at least. I think shimming stock needles might have done the same thing. Now, after some other mods, I find the midrange to be rich when the lowspeed is right. After mods, I could never get the midrange right without stumbling lean down low, no matter what I changed.
I just recently got directed from another lister to some HRC carb needles/jets for this bike designed to work with these mods and am excited to try them. There are 2 needle profiles: the leaner one has similar stepped shape to DJ, the richer one just a gradual taper throughout.
I just recently got directed from another lister to some HRC carb needles/jets for this bike designed to work with these mods and am excited to try them. There are 2 needle profiles: the leaner one has similar stepped shape to DJ, the richer one just a gradual taper throughout.
10-07-2007, 05:10 PM
#5
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
I am keen to try some 48 pilots, but not until I fit the K and N, I made need to lower the needle 1 clip then. But right now its running sweet. I would like to have a wide band AFR on the bike while riding to see exactly whats going on with it.
I have heard some people have trouble getting the HRC kit right, although all motors are different and some may respond better with it.
I have used the dynojet springs and drilled the slides. Personally with nylon slides I dont think there is much gain for drilling nylon slides. I just think its something DJ do across the board. I love their springs, they are much easier to put back in! lol.
Personally, at the end of the day. You could get better results with the standard needles. They run well standard with them. After fitting the filter and pipes just shim them to get the correct fueling and buy yourself a few different Keihin main jets and go from there.
Cliby what are your current settings. Do you have 48 pilots? Maybe try these and lower the needle one notch. You could also leave your current needle and pilot settings and drop down 1 size in your mains.
What AFR are you getting at WOT? Say if you are getting 13 to 1 you could drop down 1 main sze for eg 185/190 to 182/188 or there abouts. This wont do much to your WOT AFR possibly go to 13.2:1 and will improve mid range fueling. Remember mains still have a big influence in mid range. And you need the right AFRs all over. I think to many people are under the impression....the bigger mains the better. WRONG! AFRs have to be right to make hp and on too many occasions I have had motors running to rich in the mid then clean up top....... going down one size in mains has fixed the problem.
Keihin main jets go eg 180,182,185,188,190,192 and so on. So you have a big selection. As I have already said and you have said DJ need to do a little more development with their jet kit. All we can do is work around it with little minor changes I have listed. A word of warning. You will be starting all over again with the factory kit and could end up in the same boat. So perservere a little more and try changing mains. Most people run them to rich anyway and will only lose hp by doin this. Especially on a low comp engine. Hope this helps.
PS, Maybe there should be a section with everyones modifications and subsequent jetting changes, etc.
Cheers
Joel
I have heard some people have trouble getting the HRC kit right, although all motors are different and some may respond better with it.
I have used the dynojet springs and drilled the slides. Personally with nylon slides I dont think there is much gain for drilling nylon slides. I just think its something DJ do across the board. I love their springs, they are much easier to put back in! lol.
Personally, at the end of the day. You could get better results with the standard needles. They run well standard with them. After fitting the filter and pipes just shim them to get the correct fueling and buy yourself a few different Keihin main jets and go from there.
Cliby what are your current settings. Do you have 48 pilots? Maybe try these and lower the needle one notch. You could also leave your current needle and pilot settings and drop down 1 size in your mains.
What AFR are you getting at WOT? Say if you are getting 13 to 1 you could drop down 1 main sze for eg 185/190 to 182/188 or there abouts. This wont do much to your WOT AFR possibly go to 13.2:1 and will improve mid range fueling. Remember mains still have a big influence in mid range. And you need the right AFRs all over. I think to many people are under the impression....the bigger mains the better. WRONG! AFRs have to be right to make hp and on too many occasions I have had motors running to rich in the mid then clean up top....... going down one size in mains has fixed the problem.
Keihin main jets go eg 180,182,185,188,190,192 and so on. So you have a big selection. As I have already said and you have said DJ need to do a little more development with their jet kit. All we can do is work around it with little minor changes I have listed. A word of warning. You will be starting all over again with the factory kit and could end up in the same boat. So perservere a little more and try changing mains. Most people run them to rich anyway and will only lose hp by doin this. Especially on a low comp engine. Hope this helps.
PS, Maybe there should be a section with everyones modifications and subsequent jetting changes, etc.
Cheers
Joel
Last edited by hymey; 10-07-2007 at 05:36 PM.
10-07-2007, 05:36 PM
#6
Senior Member
SuperBike
Join Date: Jul 2005
Location: MN
Posts: 1,548
now that would be cool. I've tried to watch the needle with the carbs apart, via the hole for the main jet/tube. I recall the transition on either needle occurs over such a very narrow portion of the slide opening, and even then at relatively large openings, you can see how even a half-step (washer) might affect the fueling at 1/4 throttle openings if you were right near that transition. The leaner of the HRC needles, has a longer narrow portion (transition to midrange occurs at earlier slide opening). The richer of the needles, has a very very earlier transition point, just a taper and for most of the slide range is a thin needle: perhaps this is trying to really minimize the effect of the needle/slide and more mimic a non-CV carb?? I have no idea .
10-08-2007, 05:01 AM
#7
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
It would be interesting to see how you go with the HRC needles. The later needle I would try first.
As spoken of earlier 48 mains would be nice to try but this link suggests he had similar issues from the transition of pilot to needle circuit and richening the pilot did little to help. But its still wise to try them. Have you tried 3 turns out with 45's?
http://users.adelphia.net/~lcjhnsn/ljs_super_hawk_tuning_page.htm
Please take a close look at this guys dyno runs and notice by going up in main jet he has lost top end hp. People get over zealous with bigger mains and go backwards. I wouldnt go to big just get that lean whole fixed down low.
I think my bike is now a little rich in the top end. I am puting it on the dyno later in the week.
People have suggested the vtr runs better on stock filters than the aftermarket versions.
I'd put this to the fact that stock filters are restrictive and this creates a kind of vacuum balance point at low rpms between the butterflies and filter in the plenum. Going to K and N reduces this effect. I'd bet if you ran a decent balance pipe beneath the carbs on the inlet manifolds- (say 3/8 hose) This would solve a lot of issues people are having(including myself).
Drill and tap 1/4 inch bsp on the manifolds near the 5mm vacuum points (ie the one that goes to pet ****) Fit some 3/8 hose ends and join the two. This would smooth the engine at low rpms. I have done this in the past on inline 6 cylinders running tripple webers or SU/CV carbs and worked sweet.
I am yet reluctant to do this because I have my carbs synced nicely( by ear with hose) and checked with a vacuum gauge and they are spot on.
On another note I spoke to a tuner today and in his experience with CV carbs he has found good results tuning the mid range with mains then fine tuning the top end with needles. This sounds strange but in simple terms he told me that the slide position can vary at different rpms and throttle position and sometimes occasional low end stumbles can't be rectified with needle position because sometimes the slides are not opened enough when they need to be, eg 60 mph roll ons in top can quickly find a lean whole. In this situation the main jets have a profound effect on fueling so going bigger could solve issues then of course the needle will have to go leaner to compensate top end. Its only from years of experience with a dyno he has learnt this.
Another tuner told me to run 190/195 and tune top with the needles too. Has anyone else heard of such things?
Cheers
Joel
As spoken of earlier 48 mains would be nice to try but this link suggests he had similar issues from the transition of pilot to needle circuit and richening the pilot did little to help. But its still wise to try them. Have you tried 3 turns out with 45's?
http://users.adelphia.net/~lcjhnsn/ljs_super_hawk_tuning_page.htm
Please take a close look at this guys dyno runs and notice by going up in main jet he has lost top end hp. People get over zealous with bigger mains and go backwards. I wouldnt go to big just get that lean whole fixed down low.
I think my bike is now a little rich in the top end. I am puting it on the dyno later in the week.
People have suggested the vtr runs better on stock filters than the aftermarket versions.
I'd put this to the fact that stock filters are restrictive and this creates a kind of vacuum balance point at low rpms between the butterflies and filter in the plenum. Going to K and N reduces this effect. I'd bet if you ran a decent balance pipe beneath the carbs on the inlet manifolds- (say 3/8 hose) This would solve a lot of issues people are having(including myself).
Drill and tap 1/4 inch bsp on the manifolds near the 5mm vacuum points (ie the one that goes to pet ****) Fit some 3/8 hose ends and join the two. This would smooth the engine at low rpms. I have done this in the past on inline 6 cylinders running tripple webers or SU/CV carbs and worked sweet.
I am yet reluctant to do this because I have my carbs synced nicely( by ear with hose) and checked with a vacuum gauge and they are spot on.
On another note I spoke to a tuner today and in his experience with CV carbs he has found good results tuning the mid range with mains then fine tuning the top end with needles. This sounds strange but in simple terms he told me that the slide position can vary at different rpms and throttle position and sometimes occasional low end stumbles can't be rectified with needle position because sometimes the slides are not opened enough when they need to be, eg 60 mph roll ons in top can quickly find a lean whole. In this situation the main jets have a profound effect on fueling so going bigger could solve issues then of course the needle will have to go leaner to compensate top end. Its only from years of experience with a dyno he has learnt this.
Another tuner told me to run 190/195 and tune top with the needles too. Has anyone else heard of such things?
Cheers
Joel
10-08-2007, 06:38 AM
#8
Senior Member
Back Marker
Join Date: Sep 2007
Location: Toronto, Ontario, Canada
Posts: 203
You know, I can't help but get the impression - and keep in mind i'm new to this bike! - that the best thing to do with it is leave it alone, save for shimming the stock needles for better mid-range performance and swap out the sprockets for added "oomph". Throw in a SpeedoHealer and call it done. LOL! The rest is bling.
Sorry, just thinking out loud. (shrug)
Quickly ..... Joel, welcome to SHF!!!
Nice find with that site, great thread you have going here. I'm learning (and REALLY starting to wonder about ignition!!!!! *ahem* such a weak link in carbed bikes)
Sorry, just thinking out loud. (shrug)
Quickly ..... Joel, welcome to SHF!!!
Nice find with that site, great thread you have going here. I'm learning (and REALLY starting to wonder about ignition!!!!! *ahem* such a weak link in carbed bikes)
10-08-2007, 07:54 AM
#9
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
Thanks Slim,
I am enjoying my new bike but being a mechanical nut I cant help myself so I enjoy to fiddle with things to make them go better. Especially engines. You are right about the stock needles. I wish I had the patience to just leave things alone!
Though I see you have some interesting plans with a swap to a 929 front end. So many options!
On the topic of ignition I believe its a common mod to fit a 4 degree advance kit. It is meant to Give more torque across the board. Would work best with higher octane fuels to take advantage of it. Our fuels are different in Aus so I am unsure how the 4 degree advance kit would go.
I am keen to try adjusting the TPS. Stock it has 500 ohms. The role of the TPS on a carbed engine is similar to efi only its for ignition only. The ignition module has a built in advance curve and basically has resistors inside that increase timing as rpms increase. With the throttle shut the bike will idle with its base timing map. I am curious to see if timing is increased at idle if the TPS has greater resistance.
I am enjoying my new bike but being a mechanical nut I cant help myself so I enjoy to fiddle with things to make them go better. Especially engines. You are right about the stock needles. I wish I had the patience to just leave things alone!
Though I see you have some interesting plans with a swap to a 929 front end. So many options!
On the topic of ignition I believe its a common mod to fit a 4 degree advance kit. It is meant to Give more torque across the board. Would work best with higher octane fuels to take advantage of it. Our fuels are different in Aus so I am unsure how the 4 degree advance kit would go.
I am keen to try adjusting the TPS. Stock it has 500 ohms. The role of the TPS on a carbed engine is similar to efi only its for ignition only. The ignition module has a built in advance curve and basically has resistors inside that increase timing as rpms increase. With the throttle shut the bike will idle with its base timing map. I am curious to see if timing is increased at idle if the TPS has greater resistance.
10-08-2007, 07:58 AM
#10
Senior Member
SuperBike
Join Date: Jul 2005
Location: MN
Posts: 1,548
You are right abuot the main jets. I found leaner, within a safe A/F ratio improved topend power and I never noticed much effect on low end with stock or dynojet needles at least. Again, a different needle it might affect it more. I was really suprised how much smaller mains I needed AFTER going to the full exhaust system. Went to the smallest DJ main jet combination. Again, all of the HRC jets in this kit are significantly smaller than stock as well.
Also in the HRC parts was a plug for the main air jet in the carb to plug that opening. Said it was intended when running without the stock filter/restrictions in place. I have to say I don't understand the pressure/vacum dynamics in CV carbs well and get lost trying to guess at that point what might be happening.
bill
Also in the HRC parts was a plug for the main air jet in the carb to plug that opening. Said it was intended when running without the stock filter/restrictions in place. I have to say I don't understand the pressure/vacum dynamics in CV carbs well and get lost trying to guess at that point what might be happening.
bill
It would be interesting to see how you go with the HRC needles. The later needle I would try first.
As spoken of earlier 48 mains would be nice to try but this link suggests he had similar issues from the transition of pilot to needle circuit and richening the pilot did little to help. But its still wise to try them. Have you tried 3 turns out with 45's?
http://users.adelphia.net/~lcjhnsn/ljs_super_hawk_tuning_page.htm
Please take a close look at this guys dyno runs and notice by going up in main jet he has lost top end hp. People get over zealous with bigger mains and go backwards. I wouldnt go to big just get that lean whole fixed down low.
I think my bike is now a little rich in the top end. I am puting it on the dyno later in the week.
People have suggested the vtr runs better on stock filters than the aftermarket versions.
I'd put this to the fact that stock filters are restrictive and this creates a kind of vacuum balance point at low rpms between the butterflies and filter in the plenum. Going to K and N reduces this effect. I'd bet if you ran a decent balance pipe beneath the carbs on the inlet manifolds- (say 3/8 hose) This would solve a lot of issues people are having(including myself).
Drill and tap 1/4 inch bsp on the manifolds near the 5mm vacuum points (ie the one that goes to pet ****) Fit some 3/8 hose ends and join the two. This would smooth the engine at low rpms. I have done this in the past on inline 6 cylinders running tripple webers or SU/CV carbs and worked sweet.
I am yet reluctant to do this because I have my carbs synced nicely( by ear with hose) and checked with a vacuum gauge and they are spot on.
On another note I spoke to a tuner today and in his experience with CV carbs he has found good results tuning the mid range with mains then fine tuning the top end with needles. This sounds strange but in simple terms he told me that the slide position can vary at different rpms and throttle position and sometimes occasional low end stumbles can't be rectified with needle position because sometimes the slides are not opened enough when they need to be, eg 60 mph roll ons in top can quickly find a lean whole. In this situation the main jets have a profound effect on fueling so going bigger could solve issues then of course the needle will have to go leaner to compensate top end. Its only from years of experience with a dyno he has learnt this.
Another tuner told me to run 190/195 and tune top with the needles too. Has anyone else heard of such things?
Cheers
Joel
As spoken of earlier 48 mains would be nice to try but this link suggests he had similar issues from the transition of pilot to needle circuit and richening the pilot did little to help. But its still wise to try them. Have you tried 3 turns out with 45's?
http://users.adelphia.net/~lcjhnsn/ljs_super_hawk_tuning_page.htm
Please take a close look at this guys dyno runs and notice by going up in main jet he has lost top end hp. People get over zealous with bigger mains and go backwards. I wouldnt go to big just get that lean whole fixed down low.
I think my bike is now a little rich in the top end. I am puting it on the dyno later in the week.
People have suggested the vtr runs better on stock filters than the aftermarket versions.
I'd put this to the fact that stock filters are restrictive and this creates a kind of vacuum balance point at low rpms between the butterflies and filter in the plenum. Going to K and N reduces this effect. I'd bet if you ran a decent balance pipe beneath the carbs on the inlet manifolds- (say 3/8 hose) This would solve a lot of issues people are having(including myself).
Drill and tap 1/4 inch bsp on the manifolds near the 5mm vacuum points (ie the one that goes to pet ****) Fit some 3/8 hose ends and join the two. This would smooth the engine at low rpms. I have done this in the past on inline 6 cylinders running tripple webers or SU/CV carbs and worked sweet.
I am yet reluctant to do this because I have my carbs synced nicely( by ear with hose) and checked with a vacuum gauge and they are spot on.
On another note I spoke to a tuner today and in his experience with CV carbs he has found good results tuning the mid range with mains then fine tuning the top end with needles. This sounds strange but in simple terms he told me that the slide position can vary at different rpms and throttle position and sometimes occasional low end stumbles can't be rectified with needle position because sometimes the slides are not opened enough when they need to be, eg 60 mph roll ons in top can quickly find a lean whole. In this situation the main jets have a profound effect on fueling so going bigger could solve issues then of course the needle will have to go leaner to compensate top end. Its only from years of experience with a dyno he has learnt this.
Another tuner told me to run 190/195 and tune top with the needles too. Has anyone else heard of such things?
Cheers
Joel
10-08-2007, 08:04 AM
#11
Banned
MotoGP
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
10-08-2007, 08:06 AM
#12
Banned
MotoGP
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
10-08-2007, 08:09 AM
#13
Banned
MotoGP
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
You know, I can't help but get the impression - and keep in mind i'm new to this bike! - that the best thing to do with it is leave it alone, save for shimming the stock needles for better mid-range performance and swap out the sprockets for added "oomph". Throw in a SpeedoHealer and call it done. LOL! The rest is bling.
Sorry, just thinking out loud. (shrug)
Sorry, just thinking out loud. (shrug)
10-08-2007, 08:29 AM
#14
Senior Member
Back Marker
Join Date: Sep 2007
Location: Toronto, Ontario, Canada
Posts: 203
Makes me wonder about needle profiles and timing advance curves. You can only go so far before you start to screw it all up.
10-08-2007, 05:13 PM
#15
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
These motors are very simple in design and CV carbs have been around for a long time so it is nothing new. Any competent tuner would have no problems with it.
10-08-2007, 05:42 PM
#16
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
I realise you have a modified engine. But what
is your current jetting?
It would be interesting to see how much different your specs are.
The reason you need to go smaller in the mains is because the motor acts like a pump and with CV carbs having no accelerator pump the carbs rely on suction to work. By replacing your pipes you are effectively increasing the fuel velocity through the main jet hence you have to go smaller sometimes.
I only learnt this from tuning 2 strokes, Its quite common practice to go down in jets.
10-08-2007, 06:13 PM
#17
Senior Member
SuperBike
Join Date: Jul 2005
Location: MN
Posts: 1,548
Makes sense about the exhaust system. For mine right before I switched to the HRC needles, I had the 170/175 DJ mains, the needle on the fifth clip and 48 pilots and that was good. Too rich in the midrange, but in the real world it was running well. Before the full exhaust with engine mods and slipons, it was 180/185, fifth needleposition, 48 pilots. That was perfect AF from 7500 up and a little rich in the middle. 8541Hawk Mike has a ton of experience with these engines and mods andhas beenreally helpful.
bill
bill
10-08-2007, 07:40 PM
#18
Banned
MotoGP
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
I think you have me mixed up with someone else as The bike I'm running now is stock except for the jet kit and a pair of slip-ons.
I did have a highly modified SH that I raced a few years back and that one had a stage 2 motor in it - stage 2 cams, oversized valves with undercut seats, stage 2 springs with Ti retainers, flowed and ported heads, Hi-comp pistons on a set of Ti rods, close ratio trans with lightened flywheel, stage 2 oil pan and pick up, and on and on. She was a real beasty but the motor overpowered the chassis and when you removed all the chassis flex, then it would start to eat cases at the swing arm pivot........ Ah the good old days
Well back to your post.
I always start rich with my jetting and work my way down, something I learned fron two strokes, so I know what you are talking about. When you block the air bleeds HRC recomends that you start with 158 Fr and 162 Rear mains for a modified motor. So with a stocker you would probablly end up with something like 150 Fr and 155 Rr which would be pretty small main jets for a liter twin. The other reason to run smaller jets with the air bleeds plugged is that when they are open they are mixing air with the fuel being drawn into the mains. It is easier for the mains to draw the fuel with the bleeds open but you get less fuel as it is mixed with air.
So on to my settings, I run the stock air box and filter, #45 pilots set at 2 5\8 turns out,the stock mains (175 Fr & 178 Rr) with the HRC needles on the top clip with one .5mm shim under the front needle and two .5mm shims under the rear. I also have the HRC front slide replacement. The cut out on the slide looks to be the same as stock but the slide only has one lift hole instead of two. Let me know if you have any other questions.
Cheers,
Mike
I did have a highly modified SH that I raced a few years back and that one had a stage 2 motor in it - stage 2 cams, oversized valves with undercut seats, stage 2 springs with Ti retainers, flowed and ported heads, Hi-comp pistons on a set of Ti rods, close ratio trans with lightened flywheel, stage 2 oil pan and pick up, and on and on. She was a real beasty but the motor overpowered the chassis and when you removed all the chassis flex, then it would start to eat cases at the swing arm pivot........ Ah the good old days
Well back to your post.I always start rich with my jetting and work my way down, something I learned fron two strokes, so I know what you are talking about. When you block the air bleeds HRC recomends that you start with 158 Fr and 162 Rear mains for a modified motor. So with a stocker you would probablly end up with something like 150 Fr and 155 Rr which would be pretty small main jets for a liter twin. The other reason to run smaller jets with the air bleeds plugged is that when they are open they are mixing air with the fuel being drawn into the mains. It is easier for the mains to draw the fuel with the bleeds open but you get less fuel as it is mixed with air.
So on to my settings, I run the stock air box and filter, #45 pilots set at 2 5\8 turns out,the stock mains (175 Fr & 178 Rr) with the HRC needles on the top clip with one .5mm shim under the front needle and two .5mm shims under the rear. I also have the HRC front slide replacement. The cut out on the slide looks to be the same as stock but the slide only has one lift hole instead of two. Let me know if you have any other questions.
Cheers,
Mike
I haven't touched the airbleeds as of yet. I have read ome of your posts. The one on running lean on the bottom then raising the needle by 2 grooves and getting a stumble.
I realise you have a modified engine. But what
is your current jetting?
It would be interesting to see how much different your specs are.
The reason you need to go smaller in the mains is because the motor acts like a pump and with CV carbs having no accelerator pump the carbs rely on suction to work. By replacing your pipes you are effectively increasing the fuel velocity through the main jet hence you have to go smaller sometimes.
I only learnt this from tuning 2 strokes, Its quite common practice to go down in jets.
I realise you have a modified engine. But what
is your current jetting?
It would be interesting to see how much different your specs are.
The reason you need to go smaller in the mains is because the motor acts like a pump and with CV carbs having no accelerator pump the carbs rely on suction to work. By replacing your pipes you are effectively increasing the fuel velocity through the main jet hence you have to go smaller sometimes.
I only learnt this from tuning 2 strokes, Its quite common practice to go down in jets.
Last edited by 8541Hawk; 10-08-2007 at 08:30 PM.
10-08-2007, 07:43 PM
#19
Banned
MotoGP
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
Makes sense about the exhaust system. For mine right before I switched to the HRC needles, I had the 170/175 DJ mains, the needle on the fifth clip and 48 pilots and that was good. Too rich in the midrange, but in the real world it was running well. Before the full exhaust with engine mods and slipons, it was 180/185, fifth needleposition, 48 pilots. That was perfect AF from 7500 up and a little rich in the middle. 8541Hawk Mike has a ton of experience with these engines and mods andhas beenreally helpful.
bill
bill
Let me know if you do the shim thing and we'll get you dialed in real soon
10-09-2007, 05:10 AM
#20
dave
Squid
Join Date: Aug 2007
Location: sydney australia
Posts: 31
I have been thier I have the factory kit don't like dj kit never found they work well for me, as I have had a lot of bike & fiddled with them all 2 & 4 stroke but for the fire storm with staintune pipes std main jet seems to pull the best at top end pilot i have all three sizes 45 48 50 i found 45 pilots air bleed 2 & 3/4 turns out needle on the 4th from the top runs well. on fuel I have tryed 98 oct but I think 95 oct seems to run the best for this bike. if you don't use the bike for 3 week with 98 oct in it it would not fire up just flatten the battery seems to go off quick.
10-09-2007, 07:39 AM
#22
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
http://www.factorypro.com/tech_tunin...%20cruise.html
10-09-2007, 07:46 AM
#23
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
I have been thier I have the factory kit don't like dj kit never found they work well for me, as I have had a lot of bike & fiddled with them all 2 & 4 stroke but for the fire storm with staintune pipes std main jet seems to pull the best at top end pilot i have all three sizes 45 48 50 i found 45 pilots air bleed 2 & 3/4 turns out needle on the 4th from the top runs well. on fuel I have tryed 98 oct but I think 95 oct seems to run the best for this bike. if you don't use the bike for 3 week with 98 oct in it it would not fire up just flatten the battery seems to go off quick.
Optimax/Ultimate are both very dense fuels. Shell 95 premium is better fuel. Burns faster, better for engines with low comp, stock ignition timing.It is less dense and basically deleaded Shell 100LL. You will find your motor most probably would make better power on 95 than 98. Robbie Maddison(the freestyle rider) his father Pete proved me wrong with this on his dyno. I was gob smacked. 98 is better on high comp engines or turbocharged engines.
Do you run stock filter on your bike?
10-09-2007, 08:20 AM
#24
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
2 strokes are good to jet. You have to start a little rich or you get a dead engine, typically I find my TM 300 will 4 stroke coming on the mains when to rich, then I drop back one size and leave it. Sometimes when I ride high altitude it starts to splutter again so I drop one more in the main and its sweet.
10-10-2007, 01:12 AM
#25
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
Problem solved guys switch to 48 pilots 2.25 turns out no surging smooth idle. current settings, 48 pilot, 5th clip, 180/185 mains,
Bike is crisp and responsive but feels down on hp from 5000 to 9000rpm from stock 175/178 mains.
Might try stock mains again but want to check afr first.
Bike is crisp and responsive but feels down on hp from 5000 to 9000rpm from stock 175/178 mains.
Might try stock mains again but want to check afr first.
10-13-2007, 09:41 AM
#26
Member
Squid
Thread Starter
Join Date: Oct 2007
Location: Newcastle, Australia
Posts: 45
For those interested. I got the jetting spot on with K and N filter, no snorkel, derestricted manifold and pipes with dynojet kit.
I settled on 50 pilots, 3 turns out mixture screw, 4th clip needle, 180/185 mains.
The bike surges forward with light turn of the throttle, very responsive and the bike has more topend hp will still wheelstand under acceleration well into 3rd gear with standard sprockets.
The trick to jetting the storm is not to go to rich in the middle this makes it feel flat in midrange(like they do standard). Getting the right afr in the middle will leave the engine lean on cruise(bottom end). I was 4 turns out with 48s and still surging, 3 turns on 50. I could easily run 52s.
Airbox changes I have done on cars/bikes have resulted in much bigger jets required. Plus take into account no 2 motors are the same. With 48mm carbs on a 1000cc with derestricted airbox requires big jets to get the right afr.
Cheers
Joel
I settled on 50 pilots, 3 turns out mixture screw, 4th clip needle, 180/185 mains.
The bike surges forward with light turn of the throttle, very responsive and the bike has more topend hp will still wheelstand under acceleration well into 3rd gear with standard sprockets.
The trick to jetting the storm is not to go to rich in the middle this makes it feel flat in midrange(like they do standard). Getting the right afr in the middle will leave the engine lean on cruise(bottom end). I was 4 turns out with 48s and still surging, 3 turns on 50. I could easily run 52s.
Airbox changes I have done on cars/bikes have resulted in much bigger jets required. Plus take into account no 2 motors are the same. With 48mm carbs on a 1000cc with derestricted airbox requires big jets to get the right afr.
Cheers
Joel
07-14-2013, 02:14 AM
#27
Junior Member
Squid
Join Date: Jun 2013
Posts: 1
Hello evrbdy!
I've japan version of vtr but with "devil" exhaust. I've changed stock main jets from 162-165 to 175-178, as it should be in european version. After that it bacame too rich, as i think, after good acceleration revs fall below idle and very rear can fall to zero. Pilot screws tuning changed nearly nothing. So i removed stock washers from needles, it added about 0.5mm, but it's not enought as i think. Now i understand that i should have bought complete carb kit, maybe i'll do it later, but for now i need a "temporary" scheme. it would be god if anyone could measure length of stock european or "dynojet on 5th groove" needle, because hymey says 'With the clip in groove 5 both the stock and DJ needles are similiar length.' It'll help me to understand in wich direction i'll change the length of my stock needle. One more silly question: after making main jets bigger, do you reduce or enlarge pilot jets? Thanks!
I mean dimension #1 on this picture
I've japan version of vtr but with "devil" exhaust. I've changed stock main jets from 162-165 to 175-178, as it should be in european version. After that it bacame too rich, as i think, after good acceleration revs fall below idle and very rear can fall to zero. Pilot screws tuning changed nearly nothing. So i removed stock washers from needles, it added about 0.5mm, but it's not enought as i think. Now i understand that i should have bought complete carb kit, maybe i'll do it later, but for now i need a "temporary" scheme. it would be god if anyone could measure length of stock european or "dynojet on 5th groove" needle, because hymey says 'With the clip in groove 5 both the stock and DJ needles are similiar length.' It'll help me to understand in wich direction i'll change the length of my stock needle. One more silly question: after making main jets bigger, do you reduce or enlarge pilot jets? Thanks!
I mean dimension #1 on this picture
07-14-2013, 12:31 PM
#28
Senior Member
Superstock
Join Date: Oct 2011
Location: Pompano Beach, Fl.
Posts: 273
Good!
For those interested. I got the jetting spot on with K and N filter, no snorkel, derestricted manifold and pipes with dynojet kit.
I settled on 50 pilots, 3 turns out mixture screw, 4th clip needle, 180/185 mains.
The bike surges forward with light turn of the throttle, very responsive and the bike has more topend hp will still wheelstand under acceleration well into 3rd gear with standard sprockets.
The trick to jetting the storm is not to go to rich in the middle this makes it feel flat in midrange(like they do standard). Getting the right afr in the middle will leave the engine lean on cruise(bottom end). I was 4 turns out with 48s and still surging, 3 turns on 50. I could easily run 52s.
Airbox changes I have done on cars/bikes have resulted in much bigger jets required. Plus take into account no 2 motors are the same. With 48mm carbs on a 1000cc with derestricted airbox requires big jets to get the right afr.
Cheers
Joel
I settled on 50 pilots, 3 turns out mixture screw, 4th clip needle, 180/185 mains.
The bike surges forward with light turn of the throttle, very responsive and the bike has more topend hp will still wheelstand under acceleration well into 3rd gear with standard sprockets.
The trick to jetting the storm is not to go to rich in the middle this makes it feel flat in midrange(like they do standard). Getting the right afr in the middle will leave the engine lean on cruise(bottom end). I was 4 turns out with 48s and still surging, 3 turns on 50. I could easily run 52s.
Airbox changes I have done on cars/bikes have resulted in much bigger jets required. Plus take into account no 2 motors are the same. With 48mm carbs on a 1000cc with derestricted airbox requires big jets to get the right afr.
Cheers
Joel
Now, just humor me a little. Post up a 3rd gear roll on vid such as I did a short time ago and I'll compare bikes with a stop watch. Roll on from 2krpm in 3rd to red line. What the heck, everyone should do this as well. Come on, it'll be fun to compare!
07-14-2013, 01:55 PM
#29
Out of my mind, back in 5
MotoGP
Join Date: Nov 2006
Location: Skurup, Sweden
Posts: 6,109
Well... Since hymey haven't been on the forum since 2008... Well... You figure it out...
Thread
Thread Starter
Forum
Replies
Last Post
Anto
Classifieds
11
03-23-2011 03:27 AM
