Scooterotica

Just been informed by my mechanic that my scooter died due to a dropped piston ring, anybody any ideas why it would do that?

1) cylinder way over-bored
2) ring peg lost allowing ring to spin in its groove
3) ports not chamfered
4) exhaust port too wide for diameter of cylinder
5) simple failure of ring- worn/ damaged?
6) sods law......

you have to tell us what kit was this on

maybe a few pics of the piston and barrel might help to work out what went wrong ?

Polini 177 kit not matched or ported, PM exhaust and at the time a Delorto 30mm carb ( now running a Delorto 24/24 ) was using 2% mix now using 3%
Don't know how to put pics on here?

On your other thread i advised you check the basics cdi,ht lead etc and piston and rings.
which you have done.
I suspect the carb was not set up correctly. However i am no expert.
on my li 175 ally af barell i had the same problem.
i know its a different scooter.
it turned out the carb was jetted incorectly. Causeing a mild seize that snapped the lower piston ring.
Af managed to sort the asso piston and fit new rings.
the barrell was only lightly marked due to being steel so i was able to emery it down.
they rejetted the carb.
i run 3 to 4 % mixture. Bit rich which can cause problems. But 5 years on it hasnt been a problem.
Hopefully you will get better results with the new carb.

Robbie

Thanks for the info...it seems i had the same problem but didn't catch it early enough! hence all the damage! wether it was carb not set up right or wrong mixture who knows?

To be honest im not clued up enough on carburation to know.
its just what af told me.
many years ago i tried a 30mm dellorto on a vespa. It ran like a bag of poo. Took it off and it was better. But i dont really understand jetting and mixtures back then. Still dont. I know what it should be....but achieving it is beyond me. So i get my scooters set up or dynoed.
Personally i think its the hardest part in scooter building.
You can put on any cylinder, exhaust, gears and carb. But if the carbs wrong it wont last long.
i personally like iron cylinders for me easier to sort if they go wrong. Others prefer nicasil lined. Just personal preference i suppose.

Robbie

Me and you both, i don't know much either thats why i bought this from a shop that deals with scooters thinking it would be set up right, think i might send them the bill ( £486 ) and see if they will go halves with me.