ooheck

Forgot to mention, have already done crankcase seals and replaced air filter as this was missing when I bought the bike. Swapped carb and intake makes no difference. Its definitely a 175 (66.5mm) with a 0.5 piston. I have a spare 125 top end as well Rings aren't stuck, barrels not scored, Cranking them both over slowly by hand hand has very similar compression Will have a look at swapping heads, but can't remember noticing any difference Where/ how do you measure piston clearance?

I have two TY175's of similar vintage, one runs perfectly with crisp throttle response an plenty of low down power. The other only has power at high revs and feels like it has an elastic band between the twist grip and carb. The barrel is not marked and they have similar compression. Same fly wheel I have replaced; all the ignition system, new points, condenser, coil, plug. Timing set the same on both bikes, and I've done it 5 times to make sure. reeds to fiber and they have the same opening on the petals (9mm). (came with petals from an 50/80 with 7mm opening). When you suck through the reed block they fully seal shut. all the carb is now back as standard (came with larger carb fitted either 24 or 26mm) Exhaust decoked with no restrictions. This bike has slightly lower gearing than the good one, so can eliminate that. The only thing I haven't compared is the porting in the barrel, but this looks standard as far as I can tell and the piston. The piston has large ports but I can't decide if this will have much effect as there seems to be large and small port pistons for these. Looking at the piston in the barrel the intake transfer port in the piston never closes, but I presume it relies on the reeds closing to stop blow back through the carb. I've completely ran out of ideas other than changing the piston to one with small ports, but am not convinced thats the problem. Any ideas??