Hi all

Got the CBR up and running after moving house and I have my intermittent misfire issue back. Bike runs fine most of the time, except when warm the idle will drop and the bike will rough idle for 30 seconds and then stall most of the time. It will restart easily and keep doing this for a while and then clear randomly.

The bike revs through this misfire. If this happens while riding the problem only occurs under very light throttle at low speeds (20/30 mph). The bike has had a valve adjustment and carb balance very recently. It has also had new coil leads, caps, and plugs.

Any ideas?

Thanks all!

 

How about actual coils? Are they new? When those go out, its usually intermittent and when the bike is warmed up (they usually fail due to heat).

 

Its been so long since I worked on it, I think the coils are original. I'll arrange to get them swapped out and see if the problem goes away.

 

sparky wires too if cracked dried out etc.

 

Already replaced those, so I suppose only thing left on the ignition side is the coils.

 

good and as you look into the head where the plugs are there's no moisture and all
is bone dry ?

 

100% dry in there, yes.

 

It may be a different problem but I have experienced very similar symptoms with ethanol in the gas. Runs great at speed but blubbers and falls on its face or just plan dies at low speeds like taking off from a stop. Rev-ing up above 3,500 rpm and slipping the clutch to take off at temp but runs great when not fully warmed up.

I went up 2 jet sizes to get more fuel in and did the stick coil mod and the problem went away. The stick coil mod will make a hotter spark and help better than the rejet.
Neither one is costly and are needed to run with ethanol in the fuel.

 

Ah thats a good point, might be a good oppertunity for a stick coil mod, there are some on ebay so might try and snipe those!

Mines the same, runs spot on when not fully warm.

I if I fiddle with the choke when its running rough it just stalls, which makes me thing its not running lean at this stage.

 

Pull a plug and see if they're wet.