Small locating pin came off piston--

robin · #1 (**permalink**) 07-17-2009, 11:17 PM

50cc HT engine --The small locating pin came off the top of my piston-floated around inside and scored up the piston bad cut the top ring in half -scored up the cylinder wall--i put a new piston in and jug(piston body) -was going to buy a new engine--none available in Vancouver--engine now starts but runs on the level or downhill--whenever you load up the engine to go uphill it bogs out--is it possible the pin could have done damage to affect compression--have tried all the carb settings i can to no effect--found the pin imbedded in cylinder wall and used a chisel to take it off--it fit!!
will get my friend to check compression tomorrow.

**Norman** · #2 (**permalink**) 07-22-2009, 11:15 AM

did you replace the head and cylinder base gasket? If not you should have.
Is the new piston and cylinder the same size as the old piston wrist pin same height?
Did you use a torque wrench when you put the head back on? uneven torque on the head bolts will allow the head gasket and cylinder base gasket to leak.
Norman

robin · #3 (**permalink**) 07-22-2009, 11:24 AM

No i did not use a torque wrench that possibly is what went wrong--ran for 5 minutes-cleaned carb ran great then seized 2nd time little retainer clip came off !

**Norman** · #4 (**permalink**) 07-22-2009, 01:11 PM

toasted it again! I hate that for you.
the retainer clips need to be double checked for being in place once in place you should be able to rotate the clip by pushing on the cross wire on the clip that will help you to tell if its in the groove properly. Lot of good that advice did as its after the fact.
Did you measure piston dia verses the bore? You have to have some clearances.
Did you make sure that the rings had end gap before installing? They can't or should not butt up on the ends when in the cylinder.
Some more things to check before you try it again if you decide to rebuild it.
Norman