i recently changed my barrel from 125 to 180. i bolted it all back together, now when i try to start the engine, it just sticks. ive pulled the engine out, taken the top end off and tried to crank it without the head on. it works fine. soon as i bolt the head back on and try to manually crank it, it just sticks. what could be the issue? do the 180cc need a different head to the 125? for the record, the engine is the 4t liquid cooled leader engine. ke1ko
did you check the cam timing properly? If its wrong the valves will still be extended when the piston is near the top and they will hit each other. Does the piston sit flush or recessed or proud of the top of the barrel when its at tdc. How does this compare with how the original piston sits in its barrel?
the timing was correct. however, the piston did look like it poke slightly out of the barrel at tdc though....
this is a question for stevep.... im guessing at either different crown to pin offset or different head
funny you should say that, i was looking on ebay for cylinder heads. i found a 125, and a 180. i managed to compare the underside of the two. there is definitely a difference in the two heads. so it looks like a new head is needed too...
Of course you need to change the head. The combustion chamber in the 125 head is built for a 55mm piston where as the chamber for the 180 is built for a 65 or 65.6 mm piston. So if the 180 piston crown is clearing the barrel even slightly it will just connect with the underside of the 125 head. Hence the reason why you buy these things as a matched pair. I'd be surprised if you haven't damaged the piston if you've tried to start it and its banging off the head and coming to a dead stop
