when i got the bike it was inop really.. yoshi pipe, a/f screws closed off, etc.. was a basketcase.

i have had this apart 5 times now.. everything is spotless, carbs are synced (i have the tools) it has 138/140's for jets, and k&n filter..

it starts, purrs like a new bike, will run 140mph, and will stand up in 2nd no problem. its a great daily rider..

but... now the problem...

its running rich, (black tailpipe) no ill effects from this other than crap for mileage.. 20-30mpg and 30 is if i ride like grandma on a scooter.

the main problem is...

at 6krpm's dead on the nail it sputters like its running out of fuel.. at 6300+ its smooth and at 5700 or less its smooth. its only at 6k rpm's that it does this, which for my commute its right at 70mph which is the speed i need to travel at.. it is aggravating beyond belief, and i can't figure it out..

any ideas?

 

I am having the same issues. Just pulled my carbs off this morning and cleaned but havent put them back on yet. I was hoping it would fix it but after reading your post I am now thinking it wont. GRRRRRRRRR! So dang frustrating! I am thinking it cant be fuel or else it would be doing at the top end. I am wondering about plugs. I am a boat mechanic (although these arent boats) but all engines run on the same principle. Fuel, Compression, and spark at the right time is all you need. I have seen plugs do some crazy things in boats so I wonder if it could be that. I am gonna try it next week to see.

 

do you have an aftermarket exhaust? is the only mod you have the k&n filter?

if so, those jets may be too big..(would explain it running rich and poor mileage)

also, are the jets in the correct order on the carbs?

hopefully im not insulting intelligence here, just trying to get some more info..

From what i know though, it is pretty common for flat spots between 5-6k with k&n filters or if the carbs are over jetted.