Carb set up
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From: Sofia, Bulgaria
just to let you know...MX bikes with FCR carbs use the same pilots like Hawks N21 Series so i ordered pilots from KTM dealer
part number is 54531607048 and they are about 8$
part number is 54531607048 and they are about 8$
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MotoGP
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From: Kempner, TX
OLDER FCR's used on MX bikes use the N424-21xxx series pilot (slow) jets.
NEWER "MX FCR 39" use a N424-33xxx style jet.. MUCH different. So CRF250/450R, CRF250/450X, KX250/450F, KLX450R, ect in the OEM FCR will not work as an application.
Still good catch..
and a Harley dealer is likely to have jets for you as well.
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As cross reference i saw crf450R 2003 got N21, plus most of the ktms
All-Vehicles-
Last edited by chemomche; Dec 15, 2012 at 06:16 AM.
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Are you sure about that?
As cross reference i saw crf450R 2003 got N21, plus most of the ktms
All-Vehicles-
As cross reference i saw crf450R 2003 got N21, plus most of the ktms
All-Vehicles-
And I would not consider a 2003 as "Newer"
I have not done the research to know when the model year switch took place..
So my post was more to.. CHECK before you leap on the "all I have to do is order a pilot for a MX bike" idea.... as it is not that simple..
Still a very good idea and point for those that did not consider cross application.
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yep, i agree, not all MX bikes use it
one other aplication of the n21 series pilots is china scooter and ATV's
the "GY6" carb use keihin slow jet N21, but smaller size, about 35
however, the china companies sell bigger jets, so 48 is aviable and the price is just silly - about 2-3$
i am not sure about the quality of those 2$ jets, so i prefered ordering ktm OEM part instread on a good price
one other aplication of the n21 series pilots is china scooter and ATV's
the "GY6" carb use keihin slow jet N21, but smaller size, about 35
however, the china companies sell bigger jets, so 48 is aviable and the price is just silly - about 2-3$
i am not sure about the quality of those 2$ jets, so i prefered ordering ktm OEM part instread on a good price
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From: altoona, pa
this site might be helpful in clearing up some your questions:
Jets R Us mikuni, keihin, hitachi, holley, jets and carb parts
Jets R Us mikuni, keihin, hitachi, holley, jets and carb parts
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From: Prague - Czech
8541Hawk:
Hi, I was asked to help to tune engine of this beauti. It has PiperCross filter, 2-1 pipes are copy of racing akrapovic for VTR SP, carbs setup unknown. The pipes were on other bike with one can and worked fine, so I think it is possible to make it work, not sure if two cans make some difference.
Now it has rough low and mid revs, and engine is prone to die sometimes.
We have stock spare carbs, so my idea is to adjust these, put them on bike and see what it will do.
I would start with 50 pilots (I have these spare and with this overbored pipes maybe it could work?), 178 and 180 mains, plugged front slide hole, and shimmed needles 0.5 and 1 mm, pilots screws turns out I have no idea. Maybe two short stacks.
What would you recommend as a baseline? I followed your advices here on my bike and it runs great.
Thanks
Current bike
pipes
previous bike with these pipes
Hi, I was asked to help to tune engine of this beauti. It has PiperCross filter, 2-1 pipes are copy of racing akrapovic for VTR SP, carbs setup unknown. The pipes were on other bike with one can and worked fine, so I think it is possible to make it work, not sure if two cans make some difference.
Now it has rough low and mid revs, and engine is prone to die sometimes.
We have stock spare carbs, so my idea is to adjust these, put them on bike and see what it will do.
I would start with 50 pilots (I have these spare and with this overbored pipes maybe it could work?), 178 and 180 mains, plugged front slide hole, and shimmed needles 0.5 and 1 mm, pilots screws turns out I have no idea. Maybe two short stacks.
What would you recommend as a baseline? I followed your advices here on my bike and it runs great.
Thanks
Current bike
pipes
previous bike with these pipes
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From: Lake View Terrace, CA
We have stock spare carbs, so my idea is to adjust these, put them on bike and see what it will do.
I would start with 50 pilots (I have these spare and with this overbored pipes maybe it could work?), 178 and 180 mains, plugged front slide hole, and shimmed needles 0.5 and 1 mm, pilots screws turns out I have no idea. Maybe two short stacks.
What would you recommend as a baseline? I followed your advices here on my bike and it runs great.
Thanks
I would start with 50 pilots (I have these spare and with this overbored pipes maybe it could work?), 178 and 180 mains, plugged front slide hole, and shimmed needles 0.5 and 1 mm, pilots screws turns out I have no idea. Maybe two short stacks.
What would you recommend as a baseline? I followed your advices here on my bike and it runs great.
Thanks
This will make it a bit tougher to get everything dialed in.
Also the #50 pilots are on the large side and I have never needed to run them.
With all that, if you do go with the set up you listed I would say that first if you run two (2) short stacks, plug a lift hole in both slides (plug 1 hole with short stacks, leave both holes open with long stacks)
Then start with the pilots screws open between 1-1 1\2 turns and then use the enrichment circuit (or choke) to see what the bike wants.
Pull the **** out slightly and see if the bike runs better or worse. I would guess it will get worse, in fact you might want to start out with the stock #45 pilots as a starting point.
Though with that set up you will need to pull the plugs or get some dyno time to see where you are at as you have added many variables which make a "base-line" a difficult thing to come up with.
Let us know how it runs when you get it together and we can help you out from there.
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Joined: May 2012
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From: UK
Stephen apologies for the short response this morning. I was in a rush to go out.
Mike I don't want to disagree with you as you are more knowledgeable than myself but I would just like to point out. The 50's that are now supplied by FP, I think are there to be used with a full race exhaust. Hence the reason a lot of us go back to 48's or even 45's. Now correct me if I'm wrong but the race pipes are generally a larger bore especially at the cylinder ends and often tapered. The taper on those pipes seem to be the wrong way around. Race pipes would normally start large and then tapper off
and then taper back up as it goes into the cans.
I think it may be worth giving the 50's a go, then if less than 1.5 turns then drop down to 48's. 45's I think will be too small. But like any tuning the only thing that will really tell us what is going on would be a dyno run. Especially with a non standard set up. The 2 into 1, Pipercross filter is all going to cause difficulties.
The mains might be slightly on the small side. Maybe consider 180 182 as the piper filters I believe have more airflow than K&N. It will be interesting to see what you end up with Stephen. Keep us informed.
(:-})
Mike I don't want to disagree with you as you are more knowledgeable than myself but I would just like to point out. The 50's that are now supplied by FP, I think are there to be used with a full race exhaust. Hence the reason a lot of us go back to 48's or even 45's. Now correct me if I'm wrong but the race pipes are generally a larger bore especially at the cylinder ends and often tapered. The taper on those pipes seem to be the wrong way around. Race pipes would normally start large and then tapper off
and then taper back up as it goes into the cans.I think it may be worth giving the 50's a go, then if less than 1.5 turns then drop down to 48's. 45's I think will be too small. But like any tuning the only thing that will really tell us what is going on would be a dyno run. Especially with a non standard set up. The 2 into 1, Pipercross filter is all going to cause difficulties.
The mains might be slightly on the small side. Maybe consider 180 182 as the piper filters I believe have more airflow than K&N. It will be interesting to see what you end up with Stephen. Keep us informed.
(:-})
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From: Lake View Terrace, CA
No worries Carl....
To me, you would only need a larger dia. pipe if you raise the compression ratio thereby having a corresponding increase in exhaust pressure.
To just install a larger pipe on an otherwise stock engine IMHO would give you less power than a properly sized unit.
I don't know anything about the Pipercross filter. as I have never seen one let alone tried one, so it is a complete unknown to me.
So dyno time would be the only way to really know how this set up works and what you would need to do in order to get things dialed in.
Also I don't believe going from one muffler to two would change thing too much.
To me, you would only need a larger dia. pipe if you raise the compression ratio thereby having a corresponding increase in exhaust pressure.
To just install a larger pipe on an otherwise stock engine IMHO would give you less power than a properly sized unit.
I don't know anything about the Pipercross filter. as I have never seen one let alone tried one, so it is a complete unknown to me.
So dyno time would be the only way to really know how this set up works and what you would need to do in order to get things dialed in.
Also I don't believe going from one muffler to two would change thing too much.
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From: Prague - Czech
Ok, thank a lot guys.
48 pilots is considered option and there is not much trouble to get them. Mains I am not sure, I run 180 and 182 with hiflo paper filter and arrow pipes and it runs great, and I read sometimes that vtr f is not so sensitive to size of main jets. Anyway we have 180 and 182 ordered.
We probably try my suggested setup with short stacks, plugged both holes.
Don´t think dyno is necessary, we can use lambda to measure AF ratio, together with test run it tells me enough how it goes. I don´t expect success on first attempt :-)
I will keep you informed.
48 pilots is considered option and there is not much trouble to get them. Mains I am not sure, I run 180 and 182 with hiflo paper filter and arrow pipes and it runs great, and I read sometimes that vtr f is not so sensitive to size of main jets. Anyway we have 180 and 182 ordered.
We probably try my suggested setup with short stacks, plugged both holes.
Don´t think dyno is necessary, we can use lambda to measure AF ratio, together with test run it tells me enough how it goes. I don´t expect success on first attempt :-)
I will keep you informed.
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Squid
Joined: Oct 2012
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From: Missoula, mt
Jets and shims...where?
I have read all of the threads (thank you) regarding the carb changes. Now that I will be putting in #48 jets, where is the best place to buy them? I have seen a lot of jet kits for sale but not the jets alone. Also, if I shim the needles, where can I buy the correct thickness of shims...or should I just measure the thickness of appropriate washers?
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From: Tri State
Thought I'd share my setup.
Running D&D Slipons
PAIR removed
K&N (came with bike )
Need to check the TPS next, but the bike revs smoothly throughout jet transitions even with the K&N. Just pulled plugs when doing recent work and they look very good.
Running D&D Slipons
PAIR removed
K&N (came with bike )
Need to check the TPS next, but the bike revs smoothly throughout jet transitions even with the K&N. Just pulled plugs when doing recent work and they look very good.
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SuperSport
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From: Tarpon Springs, FL
Plugged one front lift hole, front needle shimmed to .040 total, rear shimmed to .050 total. Would this cause the rear slide to return to it's home faster and slide with much less effort than the front when acuated with a finger?
Let me add that I know the diaphragms are seated properly and have no holes, but the rear one seemed much more stretched out and seemed like the ring part that actually does the sealing was larger diameter like the whole diaphragm was stretched... Thinking back to when I cleaned them, I WAS stupid enough to get carb cleaner onto that one when it was still enclosed in the diaphragm cover. Meaning, it was exposed to solvent in an eclosed space for a while while I worked on the front carb which had the cover and diaphragm off and on the bench.
I suspect I jacked it up by doing that, eh?
Let me add that I know the diaphragms are seated properly and have no holes, but the rear one seemed much more stretched out and seemed like the ring part that actually does the sealing was larger diameter like the whole diaphragm was stretched... Thinking back to when I cleaned them, I WAS stupid enough to get carb cleaner onto that one when it was still enclosed in the diaphragm cover. Meaning, it was exposed to solvent in an eclosed space for a while while I worked on the front carb which had the cover and diaphragm off and on the bench.
I suspect I jacked it up by doing that, eh?
Last edited by supermarto; Apr 11, 2013 at 08:37 AM.
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SuperSport
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From: Tarpon Springs, FL
Cancel that. I just covered one lift hole on the faster-dropping rear slider with a small bit of tape and tried the experiment again. They both slide at the same rate that way, so actually it does make enough of a difference to notice!
road racer v2 power
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Joined: Jan 2011
Posts: 265
From: coventry england
thank you hawk i followed your instruction on how to set up the carbs as in the first post .
it works a treat i will get it on a dyno next month just to fine tune it
my set up now is
standard headers and de-baffled standard cans.
+4 ignition advancer
doctor honda stacks
stick coils
with your setup it feels strong
it works a treat i will get it on a dyno next month just to fine tune it
my set up now is
standard headers and de-baffled standard cans.
+4 ignition advancer
doctor honda stacks
stick coils
with your setup it feels strong
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Posts: 133
From: California
thank you hawk i followed your instruction on how to set up the carbs as in the first post .
it works a treat i will get it on a dyno next month just to fine tune it
my set up now is
standard headers and de-baffled standard cans.
+4 ignition advancer
doctor honda stacks
stick coils
with your setup it feels strong
it works a treat i will get it on a dyno next month just to fine tune it
my set up now is
standard headers and de-baffled standard cans.
+4 ignition advancer
doctor honda stacks
stick coils
with your setup it feels strong
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Squid
Joined: May 2013
Posts: 50
From: The Old Durty, Durham NC
I am interested in doing this to my bike in the next week or so and I had a couple of questions. I have rebuilt a couple of dirt bike/enduro carbs before, but just single carbs. Is this way harder to do? Also, I do not have any way to sync the carbs... it is okay to do this clean, and refresh without syncing them? Then next time I go to the shop have them have them sync'd?
As far as parts go, I just want to confirm, if I am doing this for a stock set-up (as far as I know I haven't been inside the carbs yet, PO said everything was bone stock), I just need to order...
-2 x #48 pilot jets - series #21
-Some #4 washers to lift the stock needles.
-beer (always helps with carb work in moderate volumes)
Is this correct? Should I get any "just in case" bits like gaskets etc?
Also, I have had excellent experiences with an overnight soak in PineSol to clean carb parts. I know carb cleaner is faster, but I have a bunch of PineSol and it is fairly low toxicity (unlike Carb cleaner). Is there any reason I should NOT do the PineSol soak?
As far as parts go, I just want to confirm, if I am doing this for a stock set-up (as far as I know I haven't been inside the carbs yet, PO said everything was bone stock), I just need to order...
-2 x #48 pilot jets - series #21
-Some #4 washers to lift the stock needles.
-beer (always helps with carb work in moderate volumes)
Is this correct? Should I get any "just in case" bits like gaskets etc?
Also, I have had excellent experiences with an overnight soak in PineSol to clean carb parts. I know carb cleaner is faster, but I have a bunch of PineSol and it is fairly low toxicity (unlike Carb cleaner). Is there any reason I should NOT do the PineSol soak?
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Posts: 6,109
From: Skurup, Sweden
Well... Any disassembly of the carbs without doing a sync afterwards is plain and simple stupid, as you won't know if what you did was any good or not... Un-sync'ed the VTR runs like crap...
Go read up on the various threads (or google) on how to make an easy and cheap tool for synchronising out of some tubing, a plank and some oil... Then do the rest once you have made yourself that tool... You will be much more happy with the result, and having a shop do the sync is throwing away money... Unless you are the type to let the guy at the filling station fill your car, clean your window, and pump your tires... Then it's justifiable...
Go read up on the various threads (or google) on how to make an easy and cheap tool for synchronising out of some tubing, a plank and some oil... Then do the rest once you have made yourself that tool... You will be much more happy with the result, and having a shop do the sync is throwing away money... Unless you are the type to let the guy at the filling station fill your car, clean your window, and pump your tires... Then it's justifiable...
Last edited by Tweety; May 17, 2013 at 08:03 AM.
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From: Phoenix, AZ
I agree.. doing a sync is quite easy, just need a boost valve and about $10 worth of supplies.
That being said, I have run the bike after changing the carbs without syncing... it pops more on decel and isn't as smooth and all that but it's not unridable. Plenty of people running around without doing it. I guess what I'm saying is that you don't have to do it all in one step, but it's not complete until you do.
After your first sync you won't even care because it really does take 5 minutes including warm up to do, so it just becomes the final assembly process. It takes longer for me to hook up the bottom of the airbox to the hoses than to sync.
That being said, I have run the bike after changing the carbs without syncing... it pops more on decel and isn't as smooth and all that but it's not unridable. Plenty of people running around without doing it. I guess what I'm saying is that you don't have to do it all in one step, but it's not complete until you do.
After your first sync you won't even care because it really does take 5 minutes including warm up to do, so it just becomes the final assembly process. It takes longer for me to hook up the bottom of the airbox to the hoses than to sync.
Out of my mind, back in 5
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Joined: Nov 2006
Posts: 6,109
From: Skurup, Sweden
I agree.. doing a sync is quite easy, just need a boost valve and about $10 worth of supplies.
That being said, I have run the bike after changing the carbs without syncing... it pops more on decel and isn't as smooth and all that but it's not unridable. Plenty of people running around without doing it. I guess what I'm saying is that you don't have to do it all in one step, but it's not complete until you do.
After your first sync you won't even care because it really does take 5 minutes including warm up to do, so it just becomes the final assembly process. It takes longer for me to hook up the bottom of the airbox to the hoses than to sync.
That being said, I have run the bike after changing the carbs without syncing... it pops more on decel and isn't as smooth and all that but it's not unridable. Plenty of people running around without doing it. I guess what I'm saying is that you don't have to do it all in one step, but it's not complete until you do.
After your first sync you won't even care because it really does take 5 minutes including warm up to do, so it just becomes the final assembly process. It takes longer for me to hook up the bottom of the airbox to the hoses than to sync.
Last edited by Tweety; May 17, 2013 at 08:20 AM.
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16214-MB0-000 JOINT, BOOST $2.66
People do all kinds of things that don't make sense to me..
It's part of the job of tuning the carbs,,, if you dont or cant do the job, no shame,, just don't. let someone that can.
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Squid
Joined: May 2013
Posts: 50
From: The Old Durty, Durham NC
Sounds good - and thanks for the advice. I will try to build the sync tool and do it. This is my initial tune up for the bike (I just got it last week), doing fluids, flushes, etc etc - and I'd love to get it as close to proper running as possible.
Plus, after looking around a bit, it seems like building the device isn't tool bad of a job. If nothing else, I'll learn something. Looks a lot easier than try to do it on the four bangers I used to ride. Just not quite as simple as my DR650
Is this a 6 or 12 beer job?
Plus, after looking around a bit, it seems like building the device isn't tool bad of a job. If nothing else, I'll learn something. Looks a lot easier than try to do it on the four bangers I used to ride. Just not quite as simple as my DR650
Is this a 6 or 12 beer job?
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MotoGP
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Posts: 4,402
From: Kempner, TX
Sounds good - and thanks for the advice. I will try to build the sync tool and do it. This is my initial tune up for the bike (I just got it last week), doing fluids, flushes, etc etc - and I'd love to get it as close to proper running as possible.
Plus, after looking around a bit, it seems like building the device isn't tool bad of a job. If nothing else, I'll learn something. Looks a lot easier than try to do it on the four bangers I used to ride. Just not quite as simple as my DR650
Is this a 6 or 12 beer job?
Plus, after looking around a bit, it seems like building the device isn't tool bad of a job. If nothing else, I'll learn something. Looks a lot easier than try to do it on the four bangers I used to ride. Just not quite as simple as my DR650
Is this a 6 or 12 beer job?
Dont forget,, while you can build the vac sticks.. you still have to BUY the booster joint to fit to the other head.. as well as a vac tee for the other line.
