I have a 93F2 I bought 2 months ago that is used as track bike only. runs well, from what I can tell, it has k+n filter and two brothers pipe.. I was told it was full exhaust, but I dont know how to verify this. I have not had carbs off yet, so I dont know what type of jetting I have. My question is this. The flat spot between 8-10k is a little frustrating coming out of turns. Is this a normal issue with F2's or can it be cleared up with jetting? I can use next lower gear to skip flat spot, but then she's winging pretty hi. Im running -1-+1 in sprockets. Any help on this would be great. Thanks.
Rick

 

I have a 91 and she pulls hard everywhere except under 5k so its not an F2 thing. Definitely can be cleared up with jetting, problem is to figure out which way to adjust. Do a few test runs. Find out whether the flat spot is worse with a cold or hot engine. After that check the plugs, white or dark? Hopefully the plugs agree. If you run better cold, your bike is rich and the plugs should be dark. If the flat spot is worse hot, you are lean and the plug should be light. Adjust main jet to the next needed size. This will probably upset the current needle position so you will have to recalibrate that as well.

 

i,d start adjustin your needles first. and if u like power then ditch the k and n filter.

 

Does the K+N rob power? If so should I use stock filter? Thanks

 

I hear that it does, but I just threw a K&N in my bike so I don't have to buy stock ones anymore then jetted for it and don't have a problem. Not like I have a Dyno in my basement to tell me if I lost half a horse power but it feels fine with proper jetting.

Switching to a stock filter probably won't fix your problem UNLESS your carbs are stock and your pipe is stock.

Needles effect around 4k-8k RPMs, 7.5-13k is Main jet. If you adjust start with the main jets like I said. once the upper RPMs feel solid, you move to needles, then you move to pilot.

 

To tell if the bike is running too rich... What if I ran 1 lap with no air filter? this would lean it out, and if it ran better I would know which way to jet. Would 1 or 2 laps with no filter be real bad? Thanks. If I was to look at the plugs now would they tell me anything.. I idle off track, idle to load, idle to unload. Might give poor reading.

 

Don't do that, what if you win the lottery and get a leaf or something sucked into your engine, not cool. lol... Plus that is TOO lean. Go by cold engine/hot engine. Just don't push 100% and up to red line on a cold engine. Check your plugs after a good session, not after you have idled.

 

For what it's worth. My main jets were stainless steal 135.. stock size. no washer under stock needle. I put 140 jets on outside carbs. and 137.5 on two inside carbs. Flat spot was fixed. Almost felt slower because it was smooth, no kick at 10k. Still ran K+N filter. Will switch to stock filter next, hope it won't require another jet change. This was just an update. Thanks to all who helped.