Hi, Does anyone know if there is a difference in the porting between the later 325 and the 340 barrels? Was it simply a bigger bore?

many thanks

The original pistons had holes in them and I think the porting was different but not 100%

Coincidentally, we measured the ports on a Model 159 barrel and a 340 barrel recently and whilst I wouldn't claim it to be accurate to the nearest thou, they seemed to measure up identically.

I think you're looking for something you don't need. Any 325 Bultaco has more than enough power. The best way to ensure it is running at it's optimum is make sure the carburettor works correctly (ie: it's not knackered or incorrectly set up, regardless of which type) and that the exhaust is repacked if it needs it. You could remove the baffles from the rear box and make it straight through like the earlier banana type silencer. Make sure the ignition is in good order.

Coincidentally, we measured the ports on a Model 159 barrel and a 340 barrel recently and whilst I wouldn't claim it to be accurate to the nearest thou, they seemed to measure up identically.

I think you're looking for something you don't need. Any 325 Bultaco has more than enough power. The best way to ensure it is running at it's optimum is make sure the carburettor works correctly (ie: it's not knackered or incorrectly set up, regardless of which type) and that the exhaust is repacked if it needs it. You could remove the baffles from the rear box and make it straight through like the earlier banana type silencer. Make sure the ignition is in good order.

You're probably right Woody, easy to ride = less marks lost.

Thanks for the advice.