First dyno run - jetting opinions?
Thread Starter
Senior Member
SuperBike
Joined: Jul 2005
Posts: 1,548
From: MN
First dyno run - jetting opinions?
well after getting my engine back together and into the bike and some initial break in, I got some first dyno numbers. Baseline on my old engine was around 104hp and 65-67 torque with slipons and stage 1 cams as the only mods. On the rebuilt engine I added HC pistons and porting the head to the stage 1 cams. Now over 112hp and 69 torque. I was hoping for more and perhaps a full exhaust would make some difference in addition to getting the jetting right on. I took a stab at some initial jetting settings after hearing from killer5280 and Shayne based on their similar mods and it actually runs pretty good. Something was wrong with the print set up on their dyno so the torque scale and curve are shifted relative to the HP numbers, but the numbers are correct and looked fine on the dyno.
I want to go logically through the jetting. The mid-range looks too rich to me, but I thought I might first go slightly larger on the main jets to see if that might yield a little more top end and then once that is optimized, then move down to the midrange. Or maybe wait till I can locate a full exhaust system. Any thoughts?
bill
I want to go logically through the jetting. The mid-range looks too rich to me, but I thought I might first go slightly larger on the main jets to see if that might yield a little more top end and then once that is optimized, then move down to the midrange. Or maybe wait till I can locate a full exhaust system. Any thoughts?
bill
Senior Member
Superstock
Joined: Jun 2006
Posts: 358
jetting would be easier if everything didnt bleed over so bad. i find its easier to set the low speed jet, then the main jet. then fine tune the needle.
and if yur going to get a full system u might as well wait to tune yur jetting till after u hav it on. or you will be back in their messing with it after u get the full system on.
if you get to a point where the airscrew is all the way in or out you need to go up or down on the idle jet, respectively. as witht he needle, ideally you dont want to be in the very top or very bottom slot, if you are its time to change something.
i have a love hate relationship with carbs, most of my friends hav sold off their carbed bikes/ atv's/ vehicles and gone FI. personally i get a kick out of whooping their high dollar FI rigs with my well set up carbed bike and ATV.
and if yur going to get a full system u might as well wait to tune yur jetting till after u hav it on. or you will be back in their messing with it after u get the full system on.
if you get to a point where the airscrew is all the way in or out you need to go up or down on the idle jet, respectively. as witht he needle, ideally you dont want to be in the very top or very bottom slot, if you are its time to change something.
i have a love hate relationship with carbs, most of my friends hav sold off their carbed bikes/ atv's/ vehicles and gone FI. personally i get a kick out of whooping their high dollar FI rigs with my well set up carbed bike and ATV.
Senior Member
SuperSport
Joined: Dec 2005
Posts: 963
From: Sunshine Coast, Australia
My best advice would be to sort out what exhaust you want, and any other mods, and then pay for a dyno tune.
I really think that is the best way to do CV carbs. I tried doing it myself, but it is just too hard on the road, and not safe when doing full throttle roll-ons.
I think it is money well spent.
I really think that is the best way to do CV carbs. I tried doing it myself, but it is just too hard on the road, and not safe when doing full throttle roll-ons.
I think it is money well spent.
Administrator
World Champion
Joined: Dec 2004
Posts: 105,287
From: Fulton, MO
Is PAIR disabled on your bike?
Looks a tad lean down low but you're at 3 turns on 48 pilots so maybe #50 pilots are in order? Yeah, mid is definitely rich. At least one position lower on the needles. Mains are actually pretty good. I was taught to aim for about 13:1 A/F ratio on our big twins (should be about the same as the RC51) and that's where you're at. I question the 180/185 mains though because there is a 182 size available. Or is this a Dynojet number? Factory/Keihin go 178/180/182/185/188/190. Top-right on this page: http://www.sudco.com/vol33/137.pdf
Looks a tad lean down low but you're at 3 turns on 48 pilots so maybe #50 pilots are in order? Yeah, mid is definitely rich. At least one position lower on the needles. Mains are actually pretty good. I was taught to aim for about 13:1 A/F ratio on our big twins (should be about the same as the RC51) and that's where you're at. I question the 180/185 mains though because there is a 182 size available. Or is this a Dynojet number? Factory/Keihin go 178/180/182/185/188/190. Top-right on this page: http://www.sudco.com/vol33/137.pdf
Senior Member
SuperSport
Joined: Aug 2004
Posts: 731
From: MICHIGAN
mmmm wow, you gained 8 hp just from HC pistons??? Can't wait to have mine next fall. I think the guys above have covered everything for the most part. Full systems are hard to come by nowadays. I think Akrapovic are the only ones who still make one but it is super expensive.
Thread Starter
Senior Member
SuperBike
Joined: Jul 2005
Posts: 1,548
From: MN
thanks. Greg, yes, PAIR is disabled and it is a dynojet kit/numbers. Azzkiker you are right about the few systems left and the price- outrageously high. For the HP gain, its hard to sort out the effect of just the pistons from the other mods (cams already in place) and the porting. From what I learned before doing it, the combination is important. I certainly didn't see a big boost from just the cams before doing the other mods.
bill
bill
Senior Member
SuperSport
Joined: Aug 2004
Posts: 731
From: MICHIGAN
Cams and ported head gave me an extra 8 hp on the dyno. I am sure the HC pistons will add 4-5 hp to my combo, hopefully even more. You need to work on your fueling and you will find more power there. I am running 50 pilots and 182/185 on a factory pro kit. BMC race filter and a full 2 bro exhaust system.
Senior Member
SuperBike
Joined: Aug 2004
Posts: 1,806
From: Atlanta, GA
The mains look about right to me, but you might try the 182 in the front carb. I don't think it will make much difference but it might be closer to right. With a stock filter and 48 pilots three (1080 degrees?) turns out I have a hard time believing you're lean, in spite of what the AF meter says. I have stock 45 pilots 2.5 turns out and it's not lean. I also have the needle on the 5th notch down and it seems a little rich to me. I suspect the same with yours.
Administrator
World Champion
Joined: Dec 2004
Posts: 105,287
From: Fulton, MO
With a stock filter and 48 pilots three (1080 degrees?) turns out I have a hard time believing you're lean, in spite of what the AF meter says. I have stock 45 pilots 2.5 turns out and it's not lean. I also have the needle on the 5th notch down and it seems a little rich to me. I suspect the same with yours.
Personally, I'd go off plug settings and driveability at low rpm over what the EGA says. If your idle is hunting up and down and the plugs are black after idling for 5 minutes then you should go with 48 pilots.
Thread Starter
Senior Member
SuperBike
Joined: Jul 2005
Posts: 1,548
From: MN
Thanks for all the suggestions. I agree about not being lean on the low end - it doesn't act that way either. I think the on the bike tuning is a good idea down low. these full throttle dyno runs don't reflect the low end always that well. I turned in the mixture screw 1/2 turn yesterday and it ran better at idle and just off idle. Then I raised the needles - I went 2 up and it now has the slightest 1/8 throttle surging around 4K, so probably lower it one and leave it till I get another exhaust.
I always learned to get the mains right first since they so broadly affect everything, then the mid then finally the low end. It becomes an obsession though - so while I agree the AF looks good up high, I won't really know till I go up or down a jet size to see the effect that has and really define the ideal. You all know the routine.
I always learned to get the mains right first since they so broadly affect everything, then the mid then finally the low end. It becomes an obsession though - so while I agree the AF looks good up high, I won't really know till I go up or down a jet size to see the effect that has and really define the ideal. You all know the routine.
Junior Member
Squid
Joined: May 2006
Posts: 8
From: Spokane, WA
Wait till you put on the new exhaust or you will have to tune the carbs twice. In my oppinion the best kit is from factory. For your application use the CRB-H77-1.7-RK. their web sight is http://factorypro.com/
Thread
Thread Starter
Forum
Replies
Last Post
