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I've installed a Yosh race-only slip-on on my R6 and I'm thinking about having it rejetted (studders a bit at low rpms).

Any suggestions on where (i.e. dealer/shop) is a good place to get a bike rejetted in the Vancouver area? I've heard that unless it's done properly, the bike could even run worse after rejetting. Isn't a dyno required to rejet? I can't imagine too many bike shops around here have a dyno.
 

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Resident Banana
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adamantium had his done @ Burnaby Kawi last month with positive results. He also has an R6 with a slipon high mount. Call Ron for pricing. You can find their number in the links area at the top.

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hsam said:
I've installed a Yosh race-only slip-on on my R6 and I'm thinking about having it rejetted (studders a bit at low rpms).

Any suggestions on where (i.e. dealer/shop) is a good place to get a bike rejetted in the Vancouver area? I've heard that unless it's done properly, the bike could even run worse after rejetting. Isn't a dyno required to rejet? I can't imagine too many bike shops around here have a dyno.
 

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If you're happy with the way it responds except at the low rpm and low throttle side of things then all you need is to have the pilot screws opened up a little.

Main jets don't do much for the problem you're describing here.

If the WOT and high rpm side of things feels a little soft then that's a different matter. It's main jets in that case.
 

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No. Down underneath the tank the carbs all have a little spot where you can adjust the gas mixure ratio for idle and light throttle applications. These are what you need to adjust. And I'm not talking about the float bowl drains either.....

Got a manual?
 

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gordopolis said:


ROTFL!

:roflmao
Hey, it's an honest mistake if you don't know what you're looking at.
 

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Bruce I have noticed a slight flat spot at 5.5k-6k rpm and again at 8-9k rpm with my Yosh ti. oval can....but for this I will need rejetting right ?
 

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Human said:
Bruce I have noticed a slight flat spot at 5.5k-6k rpm and again at 8-9k rpm with my Yosh ti. oval can....but for this I will need rejetting right ?
If it happens with full throttle then I'd say first you need a bigger main for the 8-9K range then if the 5.5-6 hasn't perked up by that time then perhaps a 0.5 mm shim under the needles. But that's just a guess. The real answer would come from Mr Dyno and a sniffer up yer tail pipe....... uh, that's the bike's tailpipe, not your's :D
 
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Everything that I've read says that rejetting is not required for just a slip on. Since, at best, you would be looking at an increase of about 3 HP with just a slip-on, dyno runs are probably just a waste of money. If I were you, I would save the money on the rejetting and dyno runs and put it towards some other mod.

If they didn't play with your carbs during the first service, I would definitely have someone adjust the fuel mixtures and possibly shim the needles. Otherwise, you can probably put it off until your next service.

I just put a full race Yoshimura duplex high mount system on my 01 6r and what you describe is sounds very similar to what I experienced, although less extreme. I decided to take mine into Pacific Yamaha to have them rejet the and the carbs. Unlike the other shops around here ( including BK ), they actually examine the system first using an exhaust gas analyser before determining what jetting changes are necessary. My bike required bigger mains, shimming the needles, and a few other adjustments.

I would definitely drop by Pacific Yamaha and talk to Yanni ( the service manager ) to go over any concerns you might have. He spent quite a bit of time answering questions before, during, and afterwards.
 

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Nite Rider
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I have a new question to add to this thread...

How do you know you're supposed to rejet a bike?
 

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Passer of Harps
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There is always room for rejetting on a bike, even stock bikes could probably benefit (albeit very little) from some carb work. It all depends on whether the difference is worth the money for you.
 
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redracer said:
Everything that I've read says that rejetting is not required for just a slip on. Since, at best, you would be looking at an increase of about 3 HP with just a slip-on, dyno runs are probably just a waste of money. If I were you, I would save the money on the rejetting and dyno runs and put it towards some other mod.

If they didn't play with your carbs during the first service, I would definitely have someone adjust the fuel mixtures and possibly shim the needles. Otherwise, you can probably put it off until your next service.

I just put a full race Yoshimura duplex high mount system on my 01 6r and what you describe is sounds very similar to what I experienced, although less extreme. I decided to take mine into Pacific Yamaha to have them rejet the and the carbs. Unlike the other shops around here ( including BK ), they actually examine the system first using an exhaust gas analyser before determining what jetting changes are necessary. My bike required bigger mains, shimming the needles, and a few other adjustments.

I would definitely drop by Pacific Yamaha and talk to Yanni ( the service manager ) to go over any concerns you might have. He spent quite a bit of time answering questions before, during, and afterwards.

Larry at PacYam is probably one of the few folks that can do a good job on a carb'd bike without a dyno. You can thank BMW for the sniffer though, I think that's why they got it!

Normally dyno runs are a big help in smoothing out the dips in the torque curve. TeeTee is right on the money when he points you towards the pilot circuit. Stock bikes are insanely lean from the factory, and while a normal slipon doesn't change the flow all that much, the full race Yosh noisemaker could do. A _reasonable_ rule of thumb, is up one size on the pilot jets, if you are getting any bog or stutter when you hit the gas. That is not a guarantee, but pretty common in the world of CV carbs.

I'm all for dynoTUNING as opposed to dynoRUNS. With one, you get to fill in the blanks on your bike, with the other you get a simple snapshot. You need at least a before and after set of runs if you are doing your own work, otherwise, you don't know if you've fixed it or made it worse. Blah blah blah..... :D



:rider
 
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I've been playing with jetting on my bike for some time . Can someone tell me if it is harmful to have the bike running a little on the lean side or the rich side. I've been getting conflicting info.
 

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Nite Rider
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And can somebody pls tell me how you know if the bike is running too lean or too rich?
 
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When you're adjusting the mixture what are the affects on the motor going to be (what kind of damage can be done) if it isn't getting enough fuel or vice versa?

The best way too learn is to get in there and make a mess :D
 

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Not Hanging Out Here
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Just don't say oops when you make the mess!!

:p ;)
 
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Ok, at the _extremes_ of both rich and lean:

Given that it isn't rich/lean enough to preclude running:

Lean: the bike will be running extremely hot during the operation of the lean circuit, be that choke, idle or mains (or a combo). This can quickly lead to death of the oil, clogging of the filter with carbonized bits large enough to be trapped. Hot spotting can take place within the water jacket where portions can overheat and cause microboils. Eventually, metal on metal contact will take place due to the fast breakdown of the oil barrier, resulting in scuffing and eventually seizing and such wonderful crap. Somewhere along the line, backfiring can occur, since periods of too-lean for combustion will occur, resulting in vapour buildup in the exhaust headers. As a 'good' combustion stroke occurs, the expansion in the cylinder head will ignite the mixture in the header, causing the 'boom bang'.

Rich: the intakes, plugs, valves and pistons etc will continually be getting washed with one of the best solvents around, ie gasoline. This will remove the 'dry' additives left on the cylinder walls after the engine is shut down, removing very quickly the scuff resistance of the motor during startup. The carbonized bits will develop a life of their own as a sort of glow plug, acting as preignition points, further screwing up the 4 cycle process. After a time, plugs will be firing more and more intermittently, allowing more and more gasoline to wash down the cylinders and contribute to acceleerated oil breakdown. If you are lucky, the engine will cease running BEFORE the oil is such sludge that it replicates engine failure as in 'lean' above.

Going strictly by the spark plugs on a 4 stroke STREET bike is problematic at best. If the pilot circuit is lean, but the mains aren't bad, the plugs may not reflect a lean condition. Vice versa is true, ie mains lean and pilot good/rich etc. Back to my recommendation of dyno tuning, especially with a sniffer to see what is going on within the engine (as reflected by the back wheel vis a vis throttle settings) and coming out the chute, via the sniffer. Anything else is just guesswork, sometimes very educated, most often, just a WAG (Wild Ass Guess).

:rider
 
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I've been getting a little bit of spitting and was worried about over-compensating.

Thanks for the info :thumbup
 
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