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hi,

ive rebuilt a 67 150 super recently, it has the origional, standard factory carb on it but i added what i believe is a sprint or sportique top end which has a deflector piston and matching head instead of the the old domed piston which i smashed to bits during removal. The scoot started without trouble, feels sweet and pulls great....doesnt miss a beat. But, on my way to the mot station, after 3/4 a mile it began to overheat, i limped tot the garage, passed the mot and limped back.

I'm wondering that i need to upjet from the 88 main jet (150 super) to a larger jet.

advice please gents.

regards, james

Bit strange there - the domed piston are the new type the deflector piston are old school. The port timmings on the old style cylinder are way short, What size carb are you running - just to be on the safe side i would over jet for now.

Have you still got the old barrel what about a rebore.

hi, its a 20 ml carb, 88 main jet. its basically the standard 150 super carb and set up. can you explain your comment about the timings ? the old cylinder was damaged beyond use by yours truly in an attempt to release the pistona. should this top end not work on these casings then ? i fugured if it was two port it would be ok

james