Scooterotica

I have just fitted a Malossi 166 kit and it has a metallic tapping/ knocking noise when running
I can't replicate this when I turn the engine by hand it seems fine
I have refitted the original barrel and piston and it's ok, no tapping
The kit was bought second hand, and although it visually looks ok there must be a problem wit it
Any ideas, the ring gap is good but cannot measure the piston bore accurately

my 172 rattles like a bag of spanners has done for 4 years never let me down

Yes I know the t5 172 had a reputation for rattling but don't know about the 166
Could it be piston slap , if so how could you tell

Measure the gap between piston and bore

Sounds like piston slap. No problems.
I've found if a Malossi 166 dont rattle, then it seizes instead.

Excellent I like that answer

i think the malossi rattle is down to the taper of the piston being more exaggerated than others ,my T5 malossi has always sounded like a tractor ,years ago before i read that i even kept changing the crank and bearings over and messing around like that, but it always sounded fine when revved up and i've had the same kit on for ten years now ,changing rings every few 1000 and no problems.