Yet another 210 issue

Schaltroller / Classic Motoscooters Vespa Largeframe
1

Ok to save me some time can someone point me the right way:

Mallossi 210
PM pipe
Timing fully retarded (err spark as late as possible)
mallossi reed valve with new reeds
PHBH 30mm with filter.
changed crank seals to be sure
no fuel pump
fitted to SS180 andusing SS180 tank

nice and smooth but pre ignites full throttle in 3rd and 4th also pre ignites worse if you drop down to 3 quaters throttle or if running at 3 qtrs downhill.

needle set in the middle, tried it fully raised but way too rich as it 4 strokes

It was on a 135 main then went upto 139 with no diffrence

B9 plug

plug is light brown, anyone running a similar set up?

2

ok so the carb at the moment is

Main 139
pilot (idle) 50
Slide 40
needle X3
needle jet AV262

3

I was thinking along the same lines on the needle and jet, vent is clear checked the fuel flow and it ***es out, I may as well fit a pump as well

4

You don’t say what your needle or needle jet is. Try an x2 needle and av266 needle jet. You’ll probably find bout 132 main jet ok. Fuel pump esential unless you keep the tank above half full always

5

try a different needla as an x3 is almost the richest needle dellorto do. goto a 266 needle jet and try an x2 needle, also check the vent in the petrol cap is not blocked