[Guy Unwin]

I left my K4 GSXR 1000 out side over a weekend. It rained and now the engine wont run above 4,500 rpm approx without misfiring. It runs fine up until then. Any suggestions anyone?

 

[Jimmy boy]

When is the last time air cleaner was cleaned?
could also be a fuel pump issue

 

[Guy Unwin]

Thanks for that. I have been advised it might be a fuel pump issue

 

[rv6john]

Thanks for that. I have been advised it might be a fuel pump issue

Welcome to the forum.

Your description of a "wont run above 4,500 rpm approx without misfiring" sounds more like an ignition problem.

Usually a fuel issue is more of a power loss or bogging at higher rpm.

Is is missing or bogging?

 

[Guy Unwin]

Its bogging. The fuel pump seems to be fine. We think it might be the throttle valve actuator. it seems a bit stiff

 

[QRO]

I would bet coil packs.

You can test the coil packs by measuring the resistance between the earth pin and each of the other pin and the ignition cap.

Its bogging. The fuel pump seems to be fine. We think it might be the throttle valve actuator. it seems a bit stiff

Do you mean bogging when revved up or when under load and accelerating.

If it is the same in either case, I'll stick with electrical. If it is worse when actually accelerating then I'd say it is fuel starvation or as you say some fuel ratio issue.

 

[rv6john]

Its bogging. The fuel pump seems to be fine. We think it might be the throttle valve actuator. it seems a bit stiff

"seems to be fine" is not a good answer. You need to do a fuel flow and pressure check to make sure it is working correctly. There are other things like o-rings and the pressure regulator that can cause low pressure or flow and hence, your issue.

 

[QRO]

One other thought .. maybe there is simply some water got into the tank? Maybe bleed the bottom of the tank out before you run it further?

 

[Guy Unwin]

Thanks for that. Will look into it. We did think that water might have got into the tank. But it starts very easily and runs cleanly up to 4,500 rpm