Rejetted the carbs...power loss at full throttle

[MB2]

'91 GS500e, Yoshimura pipe (mated to stock manifold by the looks of it), stock air filter/box.

Carbs are at 142.5, 37, 2.75 turns. I was running stock jets with the pipe but had a lot of back firing, after the rejet the back firing almost completely went away but now I have a new issue...

Through every gear I get hesitation/bog/power-loss at wide open throttle. I can get 3/4 throttle and be OK, but as soon as I rip it all the way it's an immediate power loss. Sounds to me like she's not getting enough fuel or air. I did have the air turned out 2, but after finding the power loss figured I'd try 2.75 and that should fix it...no go. Does the exact same thing, however I did notice the bike seems to pull harder (got the front tire off the ground leaving my driveway for the first test run on accident) with the 2.75 turns versus 2.

I also adjusted my valves at the same time as when I did the rejetting, but I can't imagine that would have caused the problems I'm having now.

So should I adjust my carbs more, try a washer, or what? I'm out of ideas...I'm not a carb guy.

~Scott

[pandymai]

idle air mix screw only affects the low end (idle) so turning more screws out wont really affect WOT.
it seems like youre getting really rich past the midrange. so yeah, probably a washer on the needle to improve midrange.

something you could try is: take out the airfilter but leave the airbox (make sure everything's pretty clean so you dont suck any crap into your carbs) and test the WOT. if it responds better to WOT than youre not getting air and the bike's running rich. the stock airbox is heavily restrictive.

im not a pro. so use your own judgement. just a thought though.

[MB2]

Turns out my main jet was too big. Went back to a 125 main and threw a washer in while I was at it...WOW! What a difference.

To anyone who rejets their carbs, remember not to make the mistake I did by looking at what guys did with aftermarket air filters when you have a stock one.

~Scott

[black and silver twin]

1 would probably bump that up to at least a 130 main, but yes a 142.5 with stock intake is much too big.

[pandymai]

1 would probably bump that up to at least a 130 main, but yes a 142.5 with stock intake is much too big.

+1
take it with grain of salt, but i think buddha was one of the people who said the stock piping is not nearly as restrictive as the stock airbox, so jetting too high with the stock airbox will run you rich real quick.  glad you got it sorted