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Old 24-08-11, 09:25 PM   #1
coombest
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Question Heeelp!! ZX7R running rough! :0(

Right - as seen here, I have been having a bit of trouble with my 1999 ZX7R, which had led to me leaving it in the garage for the last few months (even then it was only ridden a few times before I thought I had the head gasket problems, since I'd given up on it several months before that!).

It had stainless exhaust pipes fitted a couple of years ago and has a cut down Scorpion titanium oval can (was on my SV but was cut to 2/3rds length to remove crtash damage and fitted to the 7R)
It has a K&N air filter and was dyno'd and possibly rejetted at a garage locally to me just before I lost heart with it!
I fitted a Nissin radial master cylinder (from a GSX-R600) and Nissin 4 pot calipers (from a bandit 1200 - was fed up with regularly siezing pistons and distinctly average performance). This necessitated new RHS switchgear (from a ZX6R), throttle tube & housing (from a ZX10R - therefore 1/4 turn action). This required custom throttle cables & routing.

There is a 'flat spot' from from about 4,200rpm up to about 6,800rpm.
Within this rev range, if I open the throttle, it judders and shakes and goes nowhere fast. When you hit the 7,000-odd point, it enters banzai-loony mode and lifts the nose (in 1st-4th gears!) and sods off into the distance , as it should! The juddering seems to be slightly less obvious when the throttle is opened slooowly.

On Monday, I spent the day tinkering and did the following (amondst other stuff!):
Drained (dark yellow) fuel and replaced with fresh Super Plus (with a dash of Redex).
Sprayed carb cleaner into carb bellmouths, opened top of carbs, sprayed rubbers and wiped clean, sprayed carb cleaner into the air intakes when running.
Checked air filter and checked airbox - all good and fits pretty snugly (as snugly as it ever did, any way!).
Drained oil, refilled with cheap oil, ran to warm & drained.
Replaced oil filter (with Kawasaki genuine part) and refilled with good, semi-synth oil.
Checked all oil & water hoses. Tightened one water hose which showed signs of minor water leak.
Located carb heater system inline water filter and cleaned LOADS of crud out from it.
Checked all spark plug caps & leads (couldn't find my long reach spark plug wrench to check the low mileage irridium plugs!)
Checked exhaust system is gas tight (good at engine and can joins but there is a small amount of gas-staining at a small dent on the end cap of the can).


I'm now at a loss, as it's still almost the same as it was before.


I'm wondering if the can could be having a detrimental effect, so could try hooking up the old one (Leo Vinci race can) if I can find the adapter for it!


Any helpful suggestions would be very gratefully received!

Thanks in advance
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Old 24-08-11, 10:45 PM   #2
Lozzo
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Default Re: Heeelp!! ZX7R running rough! :0(

First stop is check the jetting is correct. From the sound of things the main jet size seems to be about right but the needle heights may need work (the inner two jets are normally a size larger than the outer two, so don't be alarmed if you find them to be different). Also, have a look to see if it has been fitted with a Dynojet kit. ZX7Rs don't suit Dynojet kits but the Factory-Pro rejet kits do work with them. If it has been Dynojetted then you may have ovalled emulsion tubes where they exit into the venturi, and the only cure for that is to start again with a standard set of carbs and ft a Factory-Pro jet kit because their needles don't wreck the emulsion tubes like Dynojet's needles do.

Have you junked all the crankcase breather recirculation crap? That is a major cause of problems with ZX7R carburation. Google for how to do it correctly - you will need a short length of 15mm copper plumbing pipe or similar to bridge the two breathers on top of the rocker cover.

HTH
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Old 25-08-11, 08:05 AM   #3
mikerj
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Default Re: Heeelp!! ZX7R running rough! :0(

I'd get the carbs out and make sure none of the various jets are blocked.
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Old 25-08-11, 08:30 AM   #4
SV650Racer
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Default Re: Heeelp!! ZX7R running rough! :0(

Jetting as Lozzo says. The ZX7R's dont like short exhausts and are fickle sods for jetting. Again as said dynojet needles wear the emmulsion tubes which will make the bike run rich.
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Old 25-08-11, 12:46 PM   #5
coombest
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Default Re: Heeelp!! ZX7R running rough! :0(

Cheers guys!
I'm pretty sure it's not got a Dynojet kit.
I'm not sure what to do with carbs, so not confident with doing much with them for fear of bolxing them up!
I was planning on trying the rebreather mod but ran out of time - will try that, as well as putting the old exhaust back. Hopefully that will sort it!
Otherwise, it looks like I'll be getting famiiar with carburettors pretty quick, as being a poor student, I can'fford to pay garage rates! :0/

Thanks for the replies guys - fingers crossed!
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Old 25-08-11, 03:25 PM   #6
hardhat_harry
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Default Re: Heeelp!! ZX7R running rough! :0(

Spraying the carb cleaner around all the external bits of the carbs without getting into the jets and float bowls aint really cleaning them.

Take carbs off and strip them down, Unscrew the loat bowls, take jets out spray down them. Spray and clean float bowls, take emulsion tubes out clean and look for signs of wear also check wear on needles.
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