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Discussion Starter #1
Hi there,
I've got a 98 P model for Racing purpose only.
It was used and in a bad shape, so Im rebuild and cleaning everything.
The carbs are my main problem.
Thanks to the workshop-manual I could identify the wrong main jets and worn floate valves and swap them.
Also the sparkplugs, sparkcables and fuelpumpe are replaced now.
But from time to time the carbs are shaking/twitching. (Don't know how to express it correctly in english^^)
For better understanding, here is a short clip from my carbs.

carbs - zx7r

Could someone give me an advise what I should do next?
Cheers
 

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Is it doing it when the bike is just idling? Or if you were to raise the revs to 3000 rpm does it do it then? To me, it looks like a slight mis-fire and the carbs, being mounted on rubber, move because of the misfire. Does the engine move or jerk as well?
 

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Discussion Starter #3
Seems just in idling and I've noticed that it's just cylinder three.
After turn the screw a 1/4 turn out it seems gone. But the motor still sounds rough. So I checked valve free play and timings. Everything is ok. So I checked the compression. On 1-3 around 115-120psi and on #4 75psi... so I think the pistonrings are worn out.. sounds like I need a swap engine?
 

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You could swap the engine but it's perfectly fine to replace the piston rings. Any garage mechanic worth his salt should be able to do this or you could go the whole hog a rebuild the engine.
Having said that, does the engine still give you a smooth ride? I mean, could you live with this issue?
 

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Sounds like you've found your problem, but also the carbs may be out of balance.

I had a van that was losing compression on one cylinder and at a standstill and ticking over the whole van would rock. Blip the throttle and smooth again. However it did up my fuel consumption a fair bit.

I go for new rings. May as well do all 4 whilst your in there.
 

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Discussion Starter #6
I've found a used engine for really cheap. So I go for the swap and the bike will be ready for the next trackday in august. I will check the old engine during offseason if there is the time, but I am more interested in getting rid of the carbs and go on fuel injection :)
 
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