I used to ride my CBR daily, until early December. It used to start perfectly and ran very strong. One day in early December, everything suddenly changed. I went out on a cold morning, started it up and left it on choke for 2 minutes. I went inside, put on my gear, came out, and it had died. It would turn over but would not fire afterwards.

Ever since then, it will start up like it used to and will run for several minutes. With the choke on, it sounds like it always did; the revs rise to about 4k and will remain there consistently. Off of choke, it will idle ok for several minutes. However, when I attempt to give it gas, it sputters and simply won't go above 3k rpm. Eventually the engine will just die, after which it will not restart for an extended period of time.

I have recently changed the oil, new air filter, new spark plugs, new fuel filter.

So the problem is: When the bike is on choke or off choke and idling, it sounds perfectly normal. The only trouble occurs when I try to give it gas, and it dies.

There weren't really any indications of the bike running poorly before this just suddenly occurred. I have no idea what's up... any ideas?

Thanks...


EDIT:

The bike is totally unmodified with the exception of a Two Brothers tailpipe and flush front turn signals. Mechanically, everything is bone stock.

 

I did this once. I had the petcock turned to off. It'd idle okay but when I gave it gas it wanted to die.

I'd check the battery/R&R/eletrical/etc. If all that checks out okay then it's the carbs.

 

Lets start from the basics and eliminate them first.

1. Check the fuel filter. I know you replaced it but as soon as you check it again it will be off the list for sure.

2. Check fuel pump. Be sure to follow the manual on this. Simply hitting the starter does not give it a proper test. If you don't have a manual please let me know and I will email to you.

3. Check all lines and hoses. I know this sounds like silly stuff but it may be that simple and you can eliminate hours of trouble shooting if it is that simple.

The way you describe it, it sounds as if the carbs are starving for fuel. To eliminate my fuel pump I ran a line directly from the tank to the carbs. Also, to eliminate the tank I ran a make-shift IV bag (gas of course) directly to the carbs. I was able to determine that my fuel pump wasnot causing the problemand continued trouble shooting else where.

If its possible can you try that and let us know the results? I have more suggestions but would like to start there if its possible.

Ender
Rival Riderz
North County San Diego

 

The fuel filter is brand new; I replaced it after the bike went bad. So I know that's not the problem.

I had the bike pretty far apart to check for hoses and for replacing the fuel filter and adjusting the throttle cable. So I doubt it's that.

Hopefully it is the fuel pump. I'll give it a look tomorrow and will be back...

Thanks.

 

The fuel tank flows fine. I can't get any flow from the fuel pump using the test prescribed in the manual. I have the fuel tank hooked up to the bike now, straight to the carbs, and it is running. I was actually able to rev it above 5krpm finally. So it appears to be a faulty fuel pump... it has no flow with the ignition ON!!!

New fuel pump here we come.

Thank you!

 

Try turning the twister thingy below the fuel **** (somebody tell me what that is).

 

The twister thinging just adjusts your idle