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Discussion Starter · #1 ·
Hello all,
I know what you're thinking, here's another idiot who needs to rebuild his carbs.
Within the last two months, I have pulled apart cleaned and jetted my carbs(factory pro). I even pulled the stack apart as I had to reseal the o-rings in between. The bike started right up and for the most part, was trouble-free. I started with the recommended factory pro specs for my setup.
Here's my current predicament: The bike is slightly rich at idle and somewhat rich between 9500-11500 rpm. I have no issues at partial or even 80%ish throttle, but a wide open pull will cause some slight breakup between the rpm range above. I know air mixture screws help with idle, I have them at the factory pro recommended 3.5 turns out. I have been meaning to lean them out (by tightening them I believe?) but haven't got to it yet. Would my upper rpm issue be consistent with this? I think it may be rich enough that the screws won't be able to lean it out enough. This is when you would switch to needle height adjustment correct? Is lowering the needle into the carb (moving the spacer up) lean the bike out more? The way I understand it is they work somewhat together, the needle sets the range and the screw dials in the exactness.
I don't think it's the main jet as it runs as it should from 11500-16000. Main jets are the recommended 155 outside, 150 inside. The pilots are up to a 40 from a 38, but off idle acceleration is pretty solid. If I remember correctly the screws are 3.5 turns out and the needle is on the third of 5 slots for height. The bike has an OEM air filter (brand new) and a scorpion slip-on.

I have been meaning to pull the tank off and just troubleshoot myself but hoping someone can save me some time.
Lastly, I'm pretty sure I have the tools to the idle air screws, but I am curious, has anyone tried adjusting their needles with the carbs still on(airbox off of course)? Does this work? Already had the carbs out a few times so I would prefer to leave them in.

Thanks in advance
- Nick
 

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UR B-hind Da 8 Ball
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1. What mods are you jetting for?
2. The air screws make idle richer by screwing them in.
3. Most aftermarket exhaust won’t have that much effect on low RPM, so I’d suggest putting the stock pilot jets back in.
4. By 9500, you should be almost fully on the main jet. Your peak HP is at around 12.5k rpm, so anything higher than that is overrun and HP drops off.
 

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Discussion Starter · #3 ·
1. What mods are you jetting for?
2. The air screws make idle richer by screwing them in.
3. Most aftermarket exhaust won’t have that much effect on low RPM, so I’d suggest putting the stock pilot jets back in.
4. By 9500, you should be almost fully on the main jet. Your peak HP is at around 12.5k rpm, so anything higher than that is overrun and HP drops off.
1. The bike was jetted because: A. Pretty much all bikes come lean from the factory, B. I ride around 800’ of elevation so the bike sees a lot of oxygen, C. The bike has the slip on, D. When I first got it, it would lean pop on decel pretty hard.
2. 10-4. Couldn’t recall.
3. I went from the 38 to the 40 per the recommendation of factory Pro.I actually called Marc when ordering and talked for a while, he’s a super cool guy to talk to. He recommended the upgraded size to get ride of the factory slight bog off idle and I have no issues on low end power with it.
4. What do you suggest I try? I have the stock 148’s and 152’s, and the 150’s and 155’s the kit came with. When I first pulled them apart a previous owner who wasn’t paying attention had them installed as “148,152,148,152” so they bike never was correct on that jet size.
 

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UR B-hind Da 8 Ball
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I don’t like being more than 3.5 turns out on air screws. Factory settings on most bikes are 2-2.5. I agree Marc knows his $h*+, but I am not sure why he would recommend going up on a fuel jet, and leaning it back out with the air screws. I’d ask him. He might say back the screws out another turn, or put the factory pilots back in and set the screws at 1 turn out. (I don’t like being less than 1 turn out on the screws either)

Are you sure the lean pop wasn’t from the AIS valve? Or, Do you have the air induction system blocked off?

You might try to drop the needles one notch and see. If it gets worse go the other way. You should be able to get to the needles by just loosening the boots and tipping the carbs back, (not having to remove the plumbing and cables)

You don’t have an aftermarket air filter do you? Those 1st Gen bikes DO NOT like aftermarket filters. Very hard to get them to run right.
 

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Discussion Starter · #5 ·
I don’t like being more than 3.5 turns out on air screws. Factory settings on most bikes are 2-2.5. I agree Marc knows his $h*+, but I am not sure why he would recommend going up on a fuel jet, and leaning it back out with the air screws. I’d ask him. He might say back the screws out another turn, or put the factory pilots back in and set the screws at 1 turn out. (I don’t like being less than 1 turn out on the screws either)

Are you sure the lean pop wasn’t from the AIS valve? Or, Do you have the air induction system blocked off?

You might try to drop the needles one notch and see. If it gets worse go the other way. You should be able to get to the needles by just loosening the boots and tipping the carbs back, (not having to remove the plumbing and cables)

You don’t have an aftermarket air filter do you? Those 1st Gen bikes DO NOT like aftermarket filters. Very hard to get them to run right.
1. That's all specs from his basic sheet that comes with the kit. I can attach a photo later when I am home. I forgot about thinking to call him but figured I would try to figure it out on my own first. I will see what he recommends.
2. I'm 99% sure the first gens don't have any emissions. No catalytic converter and no one sells block-off plates, fairly sure it doesn't have AIS.
3. Perfect, its not impossible to get them out, I'm just getting sick of doing it lol.
4. The bike has a brand new OEM Yamaha(maybe 1000 miles) air filter, Marc requires this specifically in his kits.

I could also try to put a 2003 manifold on it to lean it out some lol.
 

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UR B-hind Da 8 Ball
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This is your air induction system. Thus was typical of 90s bikes. We would usually remove all the components, plug all the hoses, and cut the pipes (#2,3,4&5) down to stubs and replace the gaskets (#1) with a pieces cut out of thin steel. Bolt the pipe stubs back in place with the new steel “blocking gaskets” (a coating of high temp silicone is a good idea)
Font Line Parallel Auto part Engineering
 

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Discussion Starter · #7 ·
This is your air induction system. Thus was typical of 90s bikes. We would usually remove all the components, plug all the hoses, and cut the pipes (#2,3,4&5) down to stubs and replace the gaskets (#1) with a pieces cut out of thin steel. Bolt the pipe stubs back in place with the new steel “blocking gaskets” (a coating of high temp silicone is a good idea) View attachment 379254
It's strange they show a part diagram for one. Possibly the California models had it? I haven't checked for air tubes behind the header, but I know for a fact I have never seen the pump by the carbs, although there was an unplugged vacuum port from one of the lines running off the carb that I removed plugged. In all my looking I can't find the existence of any AIS systems for the first gen R6's just the R1. Noticed I never clarified in the first post, the bike is a non-California model 2002 R6.
 

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UR B-hind Da 8 Ball
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I hope you didn’t plug the one in the photo (snagged from the internet). That is a vent and should be open
Motor vehicle Automotive design Automotive exterior Automotive air manifold Automotive fuel system
 

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Discussion Starter · #9 ·
I hope you didn’t plug the one in the photo (snagged from the internet). That is a vent and should be open View attachment 379255
I indeed did. Seemed goofy to me to leave it venting, figured it was one of the many mess ups from the previous owner. I hope I didn't throw that away, if not ill get it back in there. Whats the purpose of the vent? Im assuming crancase pressure but wouldn't it be going to an oil trap? Just curious what its for.
 

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UR B-hind Da 8 Ball
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Never understood it either, but that may be some of your problem. One side of the tee goes to the carb, the other goes to a small catch can (about the size of a golf ball, and then there is that open port sticking up…. ???
 

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Discussion Starter · #11 ·
Never understood it either, but that may be some of your problem. One side of the tee goes to the carb, the other goes to a small catch can (about the size of a golf ball, and then there is that open port sticking up…. ???
I figured that ball was a check valve/catch can but it seems weird to me that the vent would be upstream of the catch can. I'm thinking I kept it(hoping I didn't pitch it), if so I will reinstall it tonight and test. I am still not 100% that jetting is my issue. I did notice the bike was rich at idle and took a little to return to idle, but the top end break up seemed like it started a week or so after the jetting. At first I thought it was fuel cutting and ordered a used OEM fuel pump (had to do this on the first gen I had in high school), but with how this thing smells it has to be rich. Could also just be I never really hit WOT. The throttle pull on these is ungodly long. Never did change the pump but as of now, I don't think it's my issue.

Thank you for all the feedback, by the way, it's hard to get much response on these forums sometimes. I have been diving through all the old jetting forums for the last few weeks. I also did leave Marc(factory pro) a message earlier today so I am hoping he calls me back shortly.
 

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Discussion Starter · #12 ·
Took off work early and dig into it some. I still had the vent and reinstalled that. I also slid one of the vacuum test port lines on a hair more (possible vacuum leak?) idle is still rich but I’m gonna test it out tonight and see how she does first. Maybe all that pent up pressure was causing my breakup issue up top? Updates to come.
 

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Discussion Starter · #13 ·
Update: Putting the vent back in last night helped a bunch. My upper-end hesitation is almost completely gone. I think it's still barely rich, but it is also 90+ degrees and humid in Iowa right now, so this is the least oxygen the bike will typically see. I am also planning on switching to something more aggressive exhaust-wise, so the issue way takes care of itself. All that's left now is some tinkering with the pilot screws and needles to dial in some idle, and then keep enjoying the newfound power.
 
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