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[Help] 1989 FZR 400 won't rev past 6k rpm's


Grimmello
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Hi guys. So I'm running into an interesting situation. I have resurrected my uncle's old bike that was sitting for a while. It is now idling fine and will start in about 2 tries. However when I try to ride the bike won't rev past 6k no matter how much throttle i give it even though it can rev up to 14k. It's having trouble going above 50 mph. Does anyone know what could be going on?

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Hi, sorry to say there is just not enough info here to say what might be the problem, at best it would be a wild guess as to the cause of your problem. How long has it been stood? Have you got fresh fuel in it? have you changed the filters? and so on forever I'm afraid. Try listing the things you have repaired or replaced and from that we might get an idea of what else you need to do, even then it's all best guess time.

By the way it's usually polite to do an INTRO in the "new members" section before you do a "how do I fix my bike" question, so if you would do that next it would be appreciated.

Welcome to the YOC mate. :wavey:

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Sorry slice! Just posted, work has been kinda crazy. So far I haven't done much. All I have done so far is cleaning out the carbs a couple times trying to get it to run, changed the oil, new chain, new coolant, new gas, new rear master brake cylinder. I rode it on a country road, and I couldn't get past 55 mph and 6k rpm's, even in my top gear. I know it's a work in progress, it's just slightly frustrating right now. It idles just fine after adjusting the idle set screw. I could only roll the throttle so much until it felt like it would bog down. Thinking of getting a carb rebuild kit.

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Might just need an bit of fettling ( sorry that's "fiddling with") after any time being left bikes can be a cow to get back on the road, usually it's fuel - air or ignition that cause the most problems and yours sounds like it might be a combination of them all, try setting the bike up to the factory specs then work from there as it's easiest to start from a known quantity rather than just hitting stuff till it runs :biglaugha: Concentrate on the things that make it go not on stuff that you can add later, for instance no point buying new handle bars and grips if the thing won't run same with anything else really only fix the important things first tart it up later when you have it sorted. Good luck and come back and let us know how your doing. :jossun:

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sounds like the carbs need a strip and clean. peeps swear by seafoam as that can clean out some crud.

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Most versions of the FZR400 have an exup valve - this alters exhaust back pressure to change the state of tune dynamically. It's located where the downpipes meet, they are prone to seizing up and if the bike has been unused, it'll be seized in the closed position.

It'll probably have a chromed cover, underneath this will be a cable operated pulley (the cables may also be seized) if this pulley doesn't turn you've found the most likely cause of the problem, you can rev the engine whilst looking at the valve and see if the pulley turns, there are also calibration marks to set the pulley too. Sometimes the servo that controls the system can fail, so this is also any area to explore.

There are literally 1000s of web articles and advice about testing, servicing and repairing exup valves.

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