gsx 750 running lumpy

[dransy]

Bought a gsx 750 inazuma of a mate and its running lumpy below 4k anything over and its fine .

Carbs have been stripped and cleaned but one of the downpipes takes ages to warm up where as the others get hot quite quick . It sometimes sounds like it's missfiring .

Could it be a dodgy plug on that cylindar which the downpipe takes longer to warm up ?

I'm gonna replace all 4 plugs just waiting for pay day
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Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles

[RhynoCZ]

Have you balanced the carburetors? Yes, plugs, leads, coils matter as well.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Ichy]

It sounds spark related. I'm guessing shared coils so try swapping the lead for the other off the same coil and see if the problem moves. If it does then it'll be lead, cap, or plug. If it doesn't move then possibly fuelling, valves or cylinder. Just a process of elimination then.
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[Suntan Sid]

Swap the, apparently dodgy, plug with one of the known good ones.
If it still misfires it eliminates the dodgy plug theory.
Look at one component at a time, therefore eliminating one thing at a time!
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"Everybody needs money, that's why they call it money!"

[temeluchus]

Rotten ht lead, cap or water in the relevant carb/dirty or knackered float valve/seat
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Some shite cruiser. Now with guns and FREEDOM!

[Robby]

Temelechus is right.

It's old enough that it could be many things, but is likely to be something simple. Do the electrical things first because they're easiest and even if they aren't broken, are probably past their service life.

If that doesn't fix it, carbs. I don't know how well you cleaned them, but the two areas to focus on are the mixture circuit (very small holes, easiest to clog, doesn't get cleared out by a hard ride) or needle valves (worn seat, knackered needle rubber or spring tip that isn't springing).

[temeluchus]

The O-rings around the float valve seat on period mikunis are also prone to going hard and square and making the bikes flood.
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Some shite cruiser. Now with guns and FREEDOM!

[kev2b4]

Have got a GSX750E ( Spanish import with round headlamp) - sitting in garage for last 7 years - let me know if you want any bits off it.