Dellorto 25 tuning again / 180 FXR

Hi! I've got a mystery, changin idle jet and needle position has effect but changing main jet has practically no effect in jet range 90-120. Bike goes otherwise strong till 3/4 throttle but there is no power gain anymore after that in full throttle (main jet range). In the opposite when you close throttle from full the bike seems to gain a little bit more power in that point (no matter what the main jet size is).

I am not after top speed but good acceleration.

Jets now are 40 idle, 100 main, needle second from top. Foam filter, Arrow exhaust. Std variator 12,5g rollers.

I was wondering if there is not enough vacuum for full throttle because limited std reed valve?

 

No, the PHBL will run on a totally standard engine

My memory of the jetting on these is hazy but that sounds like a lean main jet for an open filter. Reduced power at WOT would also confirm this. Use the forum search, a lot of people used these on here back in the day and so lots of well tested setups

 

Thx for the answer, I've gone way up to 125 (main jet) where the engine started to gallop when you released WOT but no power gain. I've of course searched the net but no jet combination seems to work in my case. May be the (Arrow) exhaust...

 

Is the Arrow quite high revving? 12.5s work well with the pm59 and other high revving pipes but I'd imagine they totally ruin performance on a pipe that's closer to standard. Any heavier rollers laying around to play with?

 

I've tried 13,5 rollers but not really any chance. I'm going to try the stock pipe and find out if there's any difference...