Problem today.....

[Timbo]

I was riding back from Coventry when the engine cut out, as i was coasting to a halt i let the clutch out and the scoot fired up and eveything was fine, 5 minutes later the same happened again.When it fired up again the performance was fine,maybe a little rough and i could hear a rattle but didnt think it was coming from the engine so i kept going . At home i found that the bracket that the big (NG?) exhaust is bolted to had come away from the crank case studs.One stud was missing and the other one had a nut missing. Would this (seems obvious) have led to the engine cutting out? Would there be any damage to the engine?

[joespeed]

are you sure this was not the 'nipping 'of the piston?
regards
joe

[Timbo]

..........not sure.........

[sean brady scooters]

check for cracks in exhaust..........................

[coaster]

Timbo, if you are asking if the missing studs could cause the engine to cut out or run eratically then the answer is no. It would obviously acount for the rattle though.

[Timbo]

The exhaust system was loose at the manifold as its only attached by springs........

[Timbo]

Timbo, if you are asking if the missing studs could cause the engine to cut out or run eratically then the answer is no. It would obviously acount for the rattle though.

....No wasnt thinking this... ....but yes your right about the rattle.......anyone else any thoughts re the cutting out and any damage to the engine.....

[corrado]

Tim, potential is for the loose manifold to drag air into the chamber making it run very lean and causing it to nip up due to lack of lubrication, the next stroke of the crank would introduce fresh fuel/oil/air mix to lubricate but the cycle would keep going around until the piston expands too much because of the lack of lubrication and cooling. The piston melts (only tiny fragments at this stage) causing it to lock in the barrel, that locks the crank, which in turn locks up the drive and the rear wheel locks up, pulling in the clutch frees up the rear wheel for the scooter to coast. Within minutes if not seconds the piston cools freeing itself up and you ride on but the cycle will repeat. You need to obviously repair the exhaust and seal the leak but you also have to repair the damage to the piston and barrel, which may just need a bit of wet and dry to remove the fragments of alloy from the barrel (assuming it's cast iron) and smoothing out any score marks on the piston. Assuming the damage is minor it'll probably be OK to use again. Taking the barrel and piston off if fairly straight forward assuming the gudgeon pin comes out of the piston easily and assuming you reuse the same gaskets (or replace with same thickness ones) then all the timing etc is unaffected. To get the barrel off you'll need to remove the rear shocker for extra clearance. Worst scenario (for the barrel & piston) would be a rebore and new oversized piston.

[Timbo]

............thank you sir,have posted some pics on the Feckers.............