1998 F3 Model.

Recently, my fuel pump died on me and I put in a used F4 fuel pump and it seems to run well.

Occasion 1: After riding for 3 hours, let my bike sit for 2 hours, when I tried starting it the engine basically got flooded with gas. I was able to bump start it, and ride it around with the fuel off until it smoothed out again.

Occasion 2: After a nice 2 hour ride, I was close to my home when it suddenly started running rich and choppy at low rpm. If I gave it the beans it would smooth out around 6-7K. I was able to get home but unsure why it would randomly run rich again.

Any advice here is welcomed.

 

Looking a the specs, the f3 and f4 have the same fuel delivery pressures.
It sounds like you have a float that is sticking.

 

That makes sense. I will pull the carbs and give em a clean. Would the float be sticking down, or up? I was thinking maybe of just replacing all of the float needles.

Additionally, I noticed that this issue is exacerbated when I have a full tank of gas. I also plan on checking spark plugs to make sure they are not fowled.

 

If it were me, I would just replace the needle with new ones. The majority of the work is simply getting to them. Might as well be sure the 1st time and just put fresh ones in there. They aren’t too expensive.
If I had to guess, I would say one or more are not returning to the up position.
In a basic sense, they operate just like the float valve system in a toilet.

You may actually have an issue with a float itself but less likely.

 

Okay so I just got back from a trip. I noticed this issue I have been having is really bad with a full tank of gas. I drained the tank to about half and it runs reasonably well. I also noticed the petcock automatically drains gas when switch on or reserve when the fuel line is disconnected. I read somewhere that this should only pass fuel when there is vacuum from the engine? Is this true? I still think I have float issues, but maybe the petcock is also not good? Trying to cross off the easy tasks before going back into the carbs.

Thanks,

-Aidan

 

I have not heard that concerning the petcock. It's basically just a valve. I would fight one issue at a time. The reason why it's worse with a full tank of fuel is there is more weight/pressure pushing the fuel down the line. This further indicates there is a float issue.

 

Thanks for the help hamlin. I took the carbs off and it was very obvious I had a stuck #4 float. The bike runs a treat now. I have only noticed one small thing. Occasionally if I come to a full stop and idle after some faster riding. The bike will idle higher than normal (idles at 2k instead of my set point around 1.4k) If I give it a good rev, it drops back down to 1.4K. Im assuming this is an adjustment thing with the carbs?

 

Great to hear about the floats. Conquering a problem is a great feeling.

The current issue could be a variety of things.
Are you positive the throttle cable isn’t sticking a bit?

 

Well done on getting to the float problem and fixing it.
The revs hanging could well be a mixture issue and is slightly out, revs hanging is a classic symptom of this.

 

So I actually discovered my issue. It was a weird one. I noticed at idle, my fuel pump would be going crazy, and it would get seriously hot. Knowing that this is only supposed to work when it needs gas, I needed to fix it before my fuel pump died. Long story short, there was a big air bubble in my fuel filter. After somewhat bleeding my fuel line, the pump returned to normal and that weird rev hang thing totally stopped. Thanks everyone again for their help. I love this bike.