Loss of compression, engine turns on pulling start cord but it sounds like air leaking out somewhere, I removed head but it and the gasget looked Ok.

Peter Warner, January 2009

My victa has had a febuild when it gets ho it back fires out the decomp valve

Terry, February 2014

simple procedure.
1.remove three screws holding top cover on depending on model there may be a grill to remove first. Using pliers remove the spring steel securing clip on top of the muffler, carefully ease out muffler from exhaust port tilting to detatch the lower clip.
This will give a clear view of piston, is it scored has machine been straight gassed ? if so a rebuild is possible but this depends on the state of the cyclinder walls it possible to fit +0.20" pistons but reboring cost may prohibit this

David (New Zealand), February 2009

These engines have a decompressor - at cranking speed the compression is almost undetectable, and when functioning correctly it does indeed sound like air is leaking - it is!

Under normal circumstances, the first (half-hearted) firing stroke snaps the valve shut, and the engine will then accelerate with full compression.

Having said all that, the valves are known to fail open. As an easy way to check, unscrew the valve (it's the round object screwed into the cylinder near the carb, with a tube attached to it). Use an old spark plug to plug the hole temporarily. Attempt to start the engine - note it will take considerably more effort than usual! If sucessful, replace the valve. If not, check out the usual suspects (spark, water in fuel, etc).

phil_saunders@bigfoot.com

Phil Saunders, January 2009