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Hello, I installed a full Muzzy Titanium exhaust, K&N air filter, and Dynojet Jet Kit on my ’02 6R in early May (5/3) and I am now having some serious tuning issues. I was wondering if I could get some advice from anyone with the same or similar combo, or from any carb experts. I’m not one of them….

Here’s the deal. I live in Kentucky, and the temp is now in the high 80’s to mid 90’s. In early May, the temp was high 50’s to mid 60’s. I used Dynojet’s recommended settings: 118 jets on two outer carbs and 120’s on two inner carbs, E-clip 3rd position from top. The bike ran fine after install, with a very small flat spot around 4000rpm.

Lately, it’s gotten much worse. If I give the bike full throttle between 3500-4000 rpm, the bike simply stutters, lunges, and will not accelerate until I ease up on the throttle. In general, the bike doesn’t feel as strong as it used to, although it still pulls pretty hard at the top. Thinking the bike is too rich, I shimmed the needles to be 2.5 positions from the top. This seemed to help the ‘dead zone’ by making the window smaller. The dead zone was originally in the entire 3000-4000 range. Trying for a courser adjustment, I changed the outer jets to 116’s and the inner jets to 118’s. This seemed to clean up the response as a whole, but the dead zone is still there.

Wondering if the bike was too lean, I ran it up near redline in 3rd gear (the highest gear I felt comfortable with, for obvious reasons) and eased off the throttle. The bike did not pick up power or lunge. Throttle response above 5500 rpm is good. The bike responds almost instantaneously when chopping the throttle or dumping it from fully closed.

I don’t believe it’s a vacuum leak. I sprayed WD-40 around the carbs while running, and the bike did not stutter. Checking the spark plugs, the insulators where a dull tan and the threads had some carbon buildup. The buildup may be from running the bike between 3000-4000rpm and varying the choke to see if it made a difference (it didn’t help).

Does anyone have any ideas? If there is anyone with the same setup, what jets and needle position did you use? I know every bike is different, but I’m currently not sure where to go from here. Low speed maneuvers are very difficult, and overall power seems down. By comparison: in May after the install, the bike was most definitely stronger than stock, albeit most was at the top.

Thanks for reading and for any help or suggestions.
 

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Where do you have you mixture screws set at? I have the a full system and air filter and have my bike set up like you had it the first time. Are your carbs in sycn, that could be part of the problem also. Check the mixture and sync, see if that helps.
 

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Throw away the K&N . . . just kidding! I would go back to the original main jetting 118/120? The mains really control mostly top end performance, above 8,000 and that seems to be O.K. Midrange (4,000-8,000) glitches are controled by the needles. If it does it more when the engine is cold it is too lean and you need to move the clip toward the point of the needle raising it. If it is more when it is hot you lower the needle. You don't mention if you adjusted the idle bleed screws or not. They will affect performance below 4,000. If you haven't adjust them you might need to drill out the plugs that cover them. Open them up a turn or so. You can open the up as much as 3 1/2 turn from full in. They usually come about 2 turns out from the factory.
 

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Discussion Starter #4
Thanks for the quick responses. Would've responded sooner, but we've got people getting axed at work for 'inappropriate' surfing. Don't wanna take any chances...

While the carbs were out during the initial installation in May, the plugs covering the idle mixture screws were removed. After reinstalling the carbs, a friend of mine helping me with the install tuned them by ear, starting by setting each screw 3 turns out. At the time, it idled very smoothly and was generally responsive.

All of the carbs are currently set to 2.5 turns out. The bike idles a bit rough and I know it's not optimized, but we're currently in diagnostic mode. The mixture screws didn't seem to affect the 3500-4000rpm dead zone very much.

>>>>Are your carbs in sycn, that could be part of the problem also.

The carbs have not been syncronized. From talking to people, I get 2 different stories: 1) those who believe carb sync is merely a fine tuning procedure and won't improve the current condition very much, and 2) those who believe it makes a big difference. Considering what I've done and the age of the bike (and 7900 miles on the odo), is carb sync that critical?

>>> If it does it more when the engine is cold it is too lean and you need to move the clip toward the point of the needle raising it.

There may be a change in the way the bike runs before and after it's reach operating temp, but I haven't noticed it. Considering that the bike ran much better when the outside air temp was lower, does it make sense that the bike could be too lean instead of too rich? I could go back to the 118/120 jets, but: since none of the current changes have panned out, would it only make sense to go the opposite direction? Maybe I should try the 120 & 122 jets? Like you said, I can go the opposite direction on the needles and see if that helps.

Thanks again the for input.
 

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you install the main jet that makes the bike pull the hardest up top,then work your way down.by this i mean ,do the neddle then the low end.neddle is mid range,low is the fuel screws
 

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I'm having similar problems which I plan to post in a minute. I would say check your float heights. I adjusted min trying to fix another problem first. And it made a world of a difference for my low end response and power.
 
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