Probable fuel system/carb issues. Stumbling when riding.

[4Stroke]

Hey guys, I have an old ZXR 750 and lately as in the last week my bike has been idling very strangely, stalling at lights if I don't keep the revs up slightly but then idling fine a few minutes later.

I've actually witnessed the bike idle at 1.1k (manual recommendation for my bike) drop to 0.5k for a few seconds and jump back up to 1.1k intermittently.

Also the other day crusing along at about 80/90 on the motorway I had very bad carb/throttle stumbling problems and had to pull in to the inner lane, even then if I cranked it it didn't rev and started to stumble, and this occured at low speed with cranking open the throttle also when off the motorway.

I'm pretty competent at this stuff and I might even be able to answer my own question and say that I've been running it almost exclusively on reserve lately and have to say the reserve line in the tank never had a fuel filter so me and my father soldered one in albiet it was a bronze one off one of my dads BSA's so wasn't as fine meshed as the plastic one that was on the normal line.

I think what may have happened is alot of crap from the bottom of the tank has passed through this BSA metal filter we soldered on and probably clogged up the main inline filter and may have even passed through to the carbs but until I get the time to have a look I'm open suggestions.

Kind regards.

[hmmmnz]

clean out your carbs ect, usual shit,

my money is on valve clearances
i had no end of problems on my zxr, stripped and rebuilt the carbs so many times it just wasnt funny,

turned out all of my clearances were too tight,

bastard of a job on a h1 or h2 to change the shims, very easy on the later models,


have fun :d
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[4Stroke]

[NiteMare]

first thing to do would be to drain the float bowls, to make sure there's no water in them ...

then try the bike out again
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it ain't broke...

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[Smooth]

Before doing anything with valves, I'd remove the carbs and clean them out thoroughly. I use a high pressure bicycle track pump to clean out jets and passages.

Then set float heights, check the pilot screws etc.
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TDM850

[4Stroke]

[the grim reaper]

Sounds like float height could be an issue, although that shouldn't change over time. Could be some crap is clogging the needle slide as well.

Clean carbs, check mixture screws and balance carbs, should do the trick.

Cheers

Grim
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[4Stroke]

[4Stroke]

An update, bike pretty much broke down just off the motoway last night (luckily)

It wouldn't rev past about 4k even not under load it just backfire to hell with some crazy flames out the exhaust.

Managed to get it home by keeping it under 4k and had a look this morning. Alot of rusty water in the 4 float bowls when I drained them.

Checked for pinches on carb rubbers and all seem to be opening and such ok.

Didn't have time to fully refurb carbs as had work at 11:30 but road it to work and running very good for the moment. No stumbling or idling issues either.

[4Stroke]