Sport Bikes banner

1 - 7 of 7 Posts

·
Registered
Joined
·
209 Posts
Discussion Starter #1
i have a 98 zx7r with a full muzzy exh., a jet kit, a QA gear set, and am having a huge problem. up to about 3000 rpms it does great then it just creeps up to 8500 rpms, then it rockets back up, could this be a problem with the jet kit, or maybe the throttle responsive ignition control? please help! thanks
 

·
Registered
Joined
·
145 Posts
Did you just put the jet kit in?Have you noticed this for a while or is it recent?It could be a problem with the jets.Maybe try to clean the carbs a bit and check them.I'm not sure that it would be an ignition problem.I have heard before of flat spots coming from the carbs running too lean and carbon gumming up in them.You might want to check for that too.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #3
the jet kit was installed by the previous owner, it has been doing it since i bought it, and i just recently got the bike painted, so while it was all apart i went through the carbs to see if there was anything that i could tell was wrong, nothing. someone told me that i may need "spacers" on the jets, but i would need access to a dyno to do it properly
 

·
Registered
Joined
·
209 Posts
Discussion Starter #4
one other thing i forgot to mention, while in fifth or sixth gear and "neutral" on the throttle, (not accelerating or decelerating) it almost sounds like it has a "miss" or a stutter box, some one told me that sometimes an ignition advancer will sound that way, i have not put one on it, but the previous owner might have
 

·
Registered
Joined
·
145 Posts
If it is missing like that it might be the ignition.I thought maybe it was the carbs, but if they look fine I guess it wasn't.The timing of the ignition might be a little off as well.Have you checked the ignition and the timing yet?The owner that had installed it might not have got the timing right?Oh yeah, btw...taking your bike to a dyno would be a great idea.It would be more accurate than I could ever be.I would reccommend doing that!
 

·
second chimp in space
Joined
·
3,344 Posts
When you took the carbs apart, did you look at the needles? Did they have 5 or 6 slots for a clip to go in? If not, you do not have a jet kit (maybe you have b***** jets, but that's not good enough). If so, you may have that clip in the wrong place. The rpm range you talk about is the realm of the needle. The spacer thing is basically putting small washers under the head of the needle, to raise it a bit. If you really do have a jet kit, then you can just move the clip down a bit for the same result. Stock needles are not adjustable, hence the washers. Essentially that means giving the motor more gas in that range.

You can try finding out which kit you have (dynojet or factory pro, etc), then either getting the instructions for it (dynojet has all theirs online) or calling them. They'll tell you where the needle should be for your exhaust.

Edit: if putting it where the kit suggests doesn't solve the problem, do take it to the dyno. You can experiment with it if you like, but it may take ages.
 
1 - 7 of 7 Posts
Top