Problems With 2 Stroke Engine Starting

[leigh47]

problem with 2 stroke chainsaw. Chain and bar removed. With sparkplug out engine will turn freely. With sparkplug in engine will not turn. Plug is correct size. Any suggestions ?

[1ozzy]

First guess would be spark plug too long, but you have ruled that out.

Possibly the muffler is clogged?

Try removing the muffler, spark plug in, then see if it turns.

Check the exhaust port is clear when the muffler is removed.

[tonyav]

Probably a build up of carbon in the exhaust port.

[leigh47]

Thank you both for your suggestions. However it did turn over correctly a few min. earlier, you could feel the compressions when puling the starter rope. Now you can not turn the engine at all with the starter rope and the plug out. Have mentioned this to someone and they said it could be that petrol / oil has leaked into the crankcase/sump below the piston and on the downward stroke the piston is trying to compress this which it can not do! What do you think?

[tonyav]

Stands a good chance, will need to be stripped down to know for sure though. If you do strip it down change the piston rings anyway.