Okay, here we go. I have a '91 CBR F2 with 19k on the clock. I've cleaned and synced the carbs and replaced the spark plugs. The idle is pretty lumpy and under part throttle there's a bit of a mis-fire but as soon as I get passed maybe 10% throttle angle the misfire is gone, it's not as bad now that it's been sync'd and new plugs. I'm thinking it might be a coil or the pilot screws need to be removed and cleaned then re-adjusted. When I cleaned the carbs I did not remove the pilot screw/adjusters. Here's how it sounds now.

 

i cant tell from the vid souns ok to me. but being u have a good aftermarket pipe u probly should clean and re adjust especially if your running a useless bmc or kn filter.

 

Why doesnt anybody like K+N filters? Does a stock filter flow more air? I have both, which one flows best. I have a flat spot between 8k and 10k. Would a stock filter work better? Thanks (i might have just stollen thread, sorry)

 

Stock filter has dyno'd better, and lets through less dirt particles... It might fix your flat spot, only one way to find out.

 

ok, k n and bmc are better for bikes with ram air. we don't have that. the problem is the free er flowing filter creates too much turbulence where the your fuel atomizes there for reducing overall smoothness and power. its more evident in the mid where your needle is not fully open. your flat spot could be the filter but is more likely to be a jet kit.

 

I just recently put in a K&N just so I don't have to buy stock filters anymore. Took a lot of jetting work but it seems to work as well. The thing is that running stock is easier... Honda did the settings for you. If you put in a K&N you need to tinker a lot in order to get it to run properly.

Stock will filter better though.

As for fast tracks. I would adjust the pilot screws. Let it idle with the choke off for a few minutes and take your plugs out. Wet? brown? light/tan/dry? Turn pilots out to richen and in to lean out.

 

good info. Ill put stock in this weekend and try it. My bike is track only, so I cant do any test and tune at home on street. This is why im trying to get as much info. as I can before I try anything. At a trackday is pricey to spend alot of time tuning. Thanks guys.

 

That's what an hour on the dyno is good for.