Scooterotica

what am i missing ? running a tuned ts1 with a 34 delly and jl3 ,runs fine but when the tank gets below a quarter it starts to over rev as in fuel starvation it's allways had a fast flow tap and i've changed the needle valve fom a 300 to a 350 which i hoped had cured it.when the tanks above a quarter i can thrash it everywhere no probs,any ideas ?

Could be an airlock,drill through the petrol cap with a 2mm bit that should sort it.
Alternatively it could be down to the routing of the petrol pipe,i.e.over the frame

No!!

Are you using a fuel filter?

no filter and the cap is clear but i'll try a bigger hole in it

I take it the actual flow rate is ok?

I've had three 'fast flows' on mine , 2 were crap from the start, one of which the rubber deteriorated causing the flow rate to slow.

I think I got the current one from Cam Lam and it's fine...so far

It sounds like an airlock to me,when the tank is full it doesnt need to get as much air in to fill the gap left by the rapidly depleting petrol at full bore
The less fuel in the tank the more air needed to replace it,if it was the tap restricting the flow it would happed regardless of how much fuel is in the tank.
Time the flow rate from full,at least a pint a minute then time it from half full and see what the difference is.

Have you got this sorted yet mate?

hopefully,i've re routed the pipe under the frame and drilled out the inlet on the carb[it was half restricted] so heres hopeing