Yet another jetting question

I’m having trouble getting my scoot to run nice and crisp. It runs ok at full throttle, but bogs and stutters around 1/4-1/2 throttle…

This is my setup:

Polini head on DR177 cylinder with transfer ports between engine block and cylinder base opened up to about 3/4 the size of a polini cylinder
Timing at 18 degrees
approx 1mm squish
JL RZ EVO lefthand
Rotary valve
Dellorto phbh 28mm carb with standard slide, 55 pilot, x2 needle on 2nd clip position from top, an AV262 neelde jet and a 122 main. Idle mixture screw is set at 3,5 turns out. And I’m not running with a filter, only the rubber bellow.

Any advice would be appreciated!


Mb do a guide on them

Try a x7 needle, it is weaker on the tip

Ok, will do!

I’ve never really understood how to interpret the different needle sizes. I’ve only tried an x3 before, but that did not run very well. What other needles are there to try that could be similar to the x7?


x13 is inbetween x2/x7
x2 seem to be the needle most sold as standerd in the 28/30mm carbs
I have the needle chart somewere?
thier is a chart somwhere!? on the net which would help but buggerd if I can find it! [:)]