95 f3

I have been running the bike on gravity feed ( no fuel pump ) for awhile and it was running below average. Some days it would run OK. I had issues riding at highway speeds which from what i understand is normal with no pump, the gravity feed can't keep up with the higher supply for gas.

The other and more serious problem I've had running it this was is that some days when I pull up to a light (petcock in Reserve position) fuel seems to build up in the carbs and start coming out of the fuel IN line and even out of the bottom of the air box. It seemed to me that there was just an excess of fuel in the bowls and sitting at the light the gravity feed was putting more in there than was being used, thus it was spilling out wherever it could.

I haven't really read about anything like this in any of the 'No Fuel Pump' threads I've looked at but I had simply been combating this issue by switching my petcock to OFF position when approaching a stop. Annoying but for the most part it took care of this problem. However sometimes the reverse problem would occur, where I would be riding around at normal speeds ( under 50 ) and I would run out of gas in the bowls and the bike would surge for a little bit as it ran out of gas then die, causing me to pull over and allow the bowls to fill back up before starting it again and continuing.

To me all of this has pointed to the fact that I need a fuel pump to regulate the gas. It being a litter bit warmer out I've had the bike out a couple times and just installed the Airtech Aftermarket pump today ( https://cbrforum.com/forum/cbr-600f3...l-pump-122884/ )
I had assumed that this would fix the problem but it has actually made it worse. The bike starts and warms up just fine, but as soon as I put the petcock into ON or RESERVE, it just starts flooding the carbs with gas which causes the bowls to fill up and spill out gas like it did without the pump.

I'm completely stumped right now, I thought that the fuel pump would regulate when and how much gas went into the carbs, but this doesnt seem to be happening at all. Correct me if I'm wrong on any of these assumptions, or if you think my problem lies elsewhere.

I have replaced/cleaned and checked float movement extensively because that was a previous problem I was having, and while its possible dirty carbs or a stuck float is still a problem, it doesnt appear that way to me. The symptoms I'm experiencing feel different than what I was dealing with when the floats were sticking, and when the carbs themselves where dirty/clogged. Like I said, the bike runs fine at times, when fuel delivery is working.

Any help or suggestions would be greatly appreciated, I never would have gotten as far with the bike as I have without the wonderful community and knowledge here!

 

From my understanding of the way carbs work, I'd re-visit the floats. They are what
control the gas flow. Check the needles. The cone should have straight shoulders.
If they have a divot/curve to the sides of the tips, they are bad. You can also measure
the elevation/travel (see the manual), but they are not adjustable.

Hope this gives you a direction, Ern

 

thanks Ern, the needles are new but i think that the floats themselves may be damaged. If they were unable to float up correctly and close off the flow of fuel that would cause the overflow i'm experiencing

 

Yup and check them for leaks. i.e. if they have fuel inside them, so they won't float.

Ern

 

Sounds to me like you have an intermittent blockage in the fuel delivery, caused either by a blockage in the tank vent.or the petcock.The overflow when running can surely only be in the bowls - needle and seats or floats ? .

Try running the bike with the fuel cap open enough to let air in -
Then run the bike with the cap closed and when it dies, open the fuel cap - if it goes Whoosh then you have a blocked tank vent.