need advice for my 85 vf500f! please help!

ive been having problems with my vf500f, ive cleaned the carbs countless times, replaced parts that needed replaced, i bypassed the vacuum in the petcock. still my bike wont pull past 5000 rpm. it feels like its not getting enough gas after 5 grand, it pulls strong from 1 to five thousand rpm. ive got good spark too. i am stumped on this bike. does anybody have any advice?

 

From the '84 Factory Shop Manual:

 

CDI box?

 

thanks alot! , this should help me. do u know where i can download the whole manual?

 

I'll bet your cam timing is off a hair. We have a 'Busa 1300 sitting in the classroom that showed a horrible power curve on the DynoJet due to the intake cam sprocket having been spun from an engine seizure. The power was great until it hit high/mid range and then it dove and sputtered. If you held it wide open throttle long enough to get out of that power band it would rip open and go back to full power, but from 5500-8500 it was dead weight.

 

I support Lazy's idea of cam timing. That's also a lot easier to check than pulling off those carbs and trying to put them back on again. If it is not a cam issue i would pull the carbs off and make sure compressed air can easily pass through all the passages. I use a rubber hose fitted with a basketball pump needle and blow with my mouth to check. Just a thought, first time I cleaned my carbs I never did that, and they were sparkling clean with the exception of a blocked connection. Good luck!

 

thanks, i think that maybe my fuel pump might be bad because it ticks like crazy and is very inconsistent. could this cause poor performance?

 

vf500f

it appears that the bike has weak spark. i followed the procedure in the manual for checking the coils but it shows no continuity on the secondary side of the coil yet it still runs. how is this possible , am i missing something?