Malossi 166 advice needed

Hi all,  I have a PX125 powered Sprint with malossi 166 kit, upjetted standard 20/20 carb (115 main, BE4 mixer) and ScootRS stainless expansion pipe.

I’ve noticed a few problems with my scoot recently after taking it out for a longer than usual run, after about 50 miles it started to cut out as if it was an electrical fault.  I was terrified it was going to seize, so I kept it out of the powerband and got to my destination. Everytime I went beyond 3/4 throttle, it cuts out, then catches and starts again over and over.

The plug (I only had a B7HS handy at the time) was pretty much white, was it just that my mixture needs adjusted, running lean? Or will a colder spark plug clear it up? I haven’t had this problem before on shorter runs (less than 100 miles). Or is it simply not enough fuel and I need a bigger main and/or a bigger carb?

I have just fitted a new CDI and the stator has just been refurbished, so it’s getting a much stronger spark, could that be anything to do with it?

Any advice on a set-up to avoid this happening again would be most appreciated. I don’t thrash my scooter, I just want a nice cruising speed and a bit more to overtake if necessary.


Incidentally, this setup has been running fine up until now, I’m using 3% silkolene pro 2 and the porting has been done, crank isn’t modified and the timing is set correctly.