Running on 3 cylinders

[Guest]

Hi everyone I need your help please, I brought a 1981 GSX750E, and it has a miss that I have not been able to fix so far, I have replaced the coils,leads,caps,spark plugs, CDI box, signal gen, adjusted the valve clearances and cleaned carbys only thing left is check the wiring I guess, at idle it is only running on 3 cylinders when you really get her revving she seems to run on all four cylinders I did see flames and sparks out of the exhaust the other day, the bike has a four into one exhaust and no rear air box only just a a foam filter that sits on the back of the front air box case any suggestions?

[bonanzadave]

There is a lot of info to digest there. If I was gonna guess, and it runs like it did before the work was done, Id say its your air/fuel mixture. You'll have to give more details on the carb rebuild and what you have for jets.

Just for fun try to restrict the air a little. With a towel or something. It may be running too lean.

[gvrgsxowner]

The carbys were rebuilt an ex suzuki mechanic and he said they were all good he replaced a couple of O rings, the bike has std jets. would the fact that it does not have rear airbox could that be the problem. Compression is all good and within limits.
Will try and restrict the air flow and report back, thanks for your help.
Glenn

[bonanzadave]

the bike has std jets.

That aint gonna work with no airbox and a 4:1 header