Hi, new here, anywho...

Its a 99 CBR F4, it has lots of miles on it, bought it at 30k, and it now has 50+. Recently its being giving me a stuttering problem when I'm in first gear trying to take off, say from a street light.

The only time it happens is after the temp gauge warms up to the middle or higher. And only first gear, and sometimes into 2nd but rarely. What has me confused is it runs fine when its cold out, or if I ran the twistys with no stops, its fine all day. The minute I start commuting though, and it acts up.

I'll engage first gear, slowly let go of the clutch and give it some gas, the second I start to move from that stand still stop, it chugs and bogs down, I can keep it alive it I feather the clutch until about 4k rpm and the chugging stops. All other gears are fine.

I've done many things but all end in failures. Spark plugs are changed, clutch cable/fluid has been changed, chain brand new, I even tried swapping octane but to no avail. I've did a full fluid swap, seals, and belts swap back in Nov 2010, ran fine until recently.

I've been told it could be my fuel valve or fuel filter? But these are from friends. I wanna see what the CBR enthusiasts can tell me. Thanks again!

 

check your fuel filter and clean your carbs.

 

Run a good dose of sea foam though , that will always cure my coughing problem on mine !!!

 

+1 on the fuel filter and carb cleaning... also you could try turning up your idle just a fuzz... my bike does the same thing (bad stator makes it even worse) but it's getting a major tune up this week.

 

Gonna try the sea foam and fuel filter first. The stator I checked with a volt meter and it checks out alright. I'm running through all the wires to see if there is any breakage between em too. I've already played with the idle abit, but I could put some more effort into it. I'm trying to do everything but look at the carbs lol, its not something I have much experience with.

 

Seafoam is more of a band aid then a fix though... if you want to clean the carbs you kinda really have to take them apart.

 

Back with an update. The spark plugs, fuel filter, were replaced. and I replaced some wires that looked like they were in pretty bad shape. Had a buddy check out the carbs and the spark plug wires. Everything checks out fine.

Still no fix. And all this was after I took the f4 to a shop for a diagnostic too. They couldn't find a problem...

I recently talked to another f4 rider on a bike meet who said he had the same problem.

He stated that there might be some air in my coolant. I just need to let it out by removing a coolant hose when the problem surfaces for a short period, and then reconnecting said hose.

What do you guys think?

 

I have the same exact problem. Please keep us posted

 

I have the same thing and I think I started a thread about it a while back.

It got a bit better when I did a full coolant flush. It's still there but not as bad.
When the temp gauges goes just over half way the fan will kick in and that for some reason causes the stutter. When the fan turns off it's fine again. When the bike get's really hot and I know the slight stutter is about to start I just give it a bit more gas. It's only the first few revs of first gear that stutters.

 

I guess I'll do a coolant flush then. Enough people seem to agree, and it couldn't hurt I suppose. Possible link to your thread? looked through your info but couldn't find it.