so last august i borrowed my buddy's f2 to run the final round of the WERA North Florida season. Its a fairly stock bike, its got a pipe and the motor may or may not have some head work (came from a donor bike where the previous owner said that some engine work was done).
Well it did its job at the race track, even surprised me on how well it ran in a beat to hell stock condition in comparison to my f3 (which was fully race prepped)
It then sat in my garage from August to December around Xmas/New Year. My girl was interested in learning to ride so i figured that i would teach her on that. took a bit but i got it started. and for a couple of weeks at the beginning of the year i would take her out a couple afternoons a week on it and teach her some stuff. it would stall every now and then but nothing out of the ordinary for a new rider until i rode it.
The thing died at a red light and i had some trouble getting it started again.
but the ordeal was on the way home
i was cruising in 6th gear at about 55, and it started to stumble and act up. in order to hold 55 i had to go WOT. then it just wouldnt pull anymore so i dropped down to 5th, and then 4th. finally the bike just died 3rd, almost like it ran out of gas.
at that point i had no idea what was wrong with the bike (since there was 1/2 a tank of gas in the bike). it was weird. it was struggling to do 55 in 6th gear kinda led me to believe that maybe the gas had gone bad and the carbs were gummed up.
i didnt get any time to work on it between then and yesterday (bought a race bike, modified said race bike, sold said race bike).
i pulled it out and took the carbs off and apart. the main jets were 127.5 RD (dont know who RD is) with a Kiehin 38S pilot jet. needles were at the 3rd clip from the top (total of 5 clips). Now im coming off an F3 and thinking 127 is WAY lean, so i take out a set of F3 carbs and take out some jets. changed the pilot jets to Kiehin 40s and the main jets to 135 Mikunis.
called another buddy who said that i should have checked the plugs first to see if i was running too rich or too lean. i removed them and they seemed ok, much better than rich plugs ive pulled. if anything they were a tad on the lean side of being fine.
i just need another set of eyes on this analisis. I cleaned the carbs throuroughly and put in some nice new gas. buttoned everything back up and have killed the battery twice trying to get it started again.

 

Leak/disconnected vacuum line from carb1 to the petcock?

 

got it fixed.
wound up the petcock was clogged.
went back to the smaller jets as well

 

well maybe not completely fixed, i got it started and it idles.
so this morning i took the stock headers and super trap pipe off and threw on a full Yosh system that i had in the garage. the can was dented up a bit but no holes in it or anything.
with the stock headers and the Supertrap pipe i couldnt feel anything coming out of the canister. The Yosh system fixed that right up and it sounded healthier as well, aside from the cam chain noise, which is quite prevelent, and why i was also looking for an MCCT.
i took it for a test ride, and 1st gear feels great all the way to redline, and 2nd gear below about 5000rpm feels fine, but anything upwards of about 5K or 3rd through 6th gear and it just stumbles and struggles. no matter the throttle input it is just jerky and stumbly and feels like its running out of gas. but put it back in 1st and its super responsive and smooth. (the RMPs are guesses as i dont have any guages but from speed and gearing and general feel compared to my old F3 it felt like around 5000rpm)
i brought it back in, checked the exhaust and there isnt any black or white residue to tell me if im rich or lean. i know its richer than before with the 40 pilot rather than the 38, but i put the 127.5 back in yesterday so its not that much richer. and the spark plugs werent black or white so i assumed that the jetting previously was acceptable.

i just need to know why its running like crap now that it is running...

 

CDI issue?

 

your jetting is still off. i had the same problem with my f3 when i had it jetted.
here is the dyno jet instructions for a stage 1 for your f2 plus the biggest main jet for them is a dj126. good luck http://www.dynojet.com/pdf/1140.pdf

 

what kinda air filter u running?

 

swapped CDIs and its not that.
I believe its running a stock filter. im more familiar with the F3 air box than the F2, but there is a solid plastic plate and there is an orange paper filter in the middle.

i may head down to the shop today and see if they have any jets for the F2 small enough.
thanks for the chart white knuckles

 

i had a somewhat similar problem on my bike. i thought it was the petcock because i would be riding and it would do that then i would quick flip the petcock off and it would run fine for a little bit then it would chug and so on.... i took the carbs off to clean them and to my suprise they were sparkling clean on the inside. the only thing i noticed was coming out of my #2 cylinder was a vaccum fitting just like the one out of my #1 that goes to the petcock. i talked to my mechanic buddy and he said plug it. so just to double check i went to the spare motor i have that i am going to build and sure enough its suppsed to be plugged. so i plugged it and it seemed to work. so i would say take a look, make sure your vaccum line to your petcock isnt leaking at all and see if there is an open hose coming out of cylinder #2, if there is plug it and try it again

 

so i went back, put in 4 new spark plugs, put on another set of ignition coils and plug wires, removed the main jet holders and cleaned them, replaced 2 of the boots that had slight cracks. buttoned it back together. didnt fix the problem.
the jetting doesnt make sense why it would work great last summer and now it wont. ive got a guy sending me some jets for it though.
Brown I'll have to check that tomorrow as right now its pouring outside. but also it doesnt matter what position the petcock is in, i still have the same issues, on or reserve.