Well, I was out in my shop this weekend and I LOOKED at my bike. Does that count??

 

I'm surprised that the Valve clearances havent been mentiones, my baby was acting up like yours and nothing but a good valve adjusment job worked..

Maybe your valves are so tight that they wont close completely and fuel os not pulled into the chamber (at high revs it seals just fine)

 

point taken. I have fixed my issue on my bike but I have not checked the valve clearance in a while. Ill have to check that some time before winter ends.. ahhh the best time to set down your bike and just work on it. most riders hate winter, but i think of it as an opportunity!!!

 

 

So that vacuum hole at the bottom is required for the diaphragm so the vacuum wont rip it in two. I have had to rebuild it again with the proper rebuild kit soooo ignore the past posts. but again fixing it to where the vacuum is fixed again has cleared my issue. I have been working with Tacoma Motor Sports, and a motorcycle mechanic on this issue of mine, and so far all I have done to fix this is correct the valve clearance to make sure the timeing is correct, repaired the petcock valve to a working stock condition, cleaned and re-jetted the carbs, and baught a new Regulator Rectifier and installed it. it now purrs like a champ and throttle response is soo much better. honestly alot of it wasnt just for the stutter issue, but my bike had alot more problems. I had a number of issues that consisted of improper throttle responsae, charging issue, delayed start, and a stutter under 300rpms. which the vaccum repair from the petcock valve is what really made the differnace on the 300rpm stutter issue.

 

I ordered the petcock repair kit yesterday. When I put it in I'll let you guys know how it turns out. I truly believe it is the reason for the rough running. Mine has resorted to leaking gas out onto the ground now. I'm sure it has diluted my oil as well.

 

+1
Valves, coils, carb sync and carb COMPLETE cleaning. My bike had all the same issues and after all those fixes.. Ran like new.

 

Yes, I agree. After this fix, if I'm still having trouble, I'll check the others you've mentioned.

I forgot to mention that it surges while cruising. Cleans right up if I'm accelerating hard.

 

I put the petcock repair kit on my bike and it cleaned up the stumble considerably. I had all the body work off and needed to change the chain and sprockets so I didn't take it out on the highway to see if the stutter went away but I'm sure it has. I'll let you all know as soon as I get my hands on a chain link peening tool to finish my chain and sprocket install.

 

[QUOTE=Optimus_Prime;1174106]My first thought is that the bike might not be firing on all cylinders. It would be more noticable at lower rpm and once the revs pick up the engine would run better. You said you changed the spark plugs - I'd check they are all giving a spark, make sure they are fitted correctly and that the leads are attached firmly and in the correct position for firing order.

As far as I know, the popping on deceleration comes from air entering the exhaust system and mixing with unburned fuel, causing it to ignite. So, you may have a leak somewhere. If you have a cyclinder not firing then that would be pumping fuel into the exhaust and adding to the popping situation too.[/QUOT

Hello from MALTA. I know my bike is not a CBR but I m facing the same problem. It is a 2002 honda hornet cb600f2. Had the same problem when it warms up. I changed the ignition coils, changed new spark plugs. Serviced the carburetors and even changed the fuel petcok diaphram. Yesterday I got stuck in traffic and the bike warmed up. The fan came on and after a few seconds it started to work bad. I kept it on 3000rpm and if you accelerate it would go without any problems. I dont know what I m going to do more. Someone can help me please?
Thank you