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Exhaust Valve on mountfield mower?

On taking the head off my mountfield rv150/sp534 i notice the exhaust valve is slightly open on the compresion stroke should this happen?everything else seems to happen as it should . The inlet and exhaust valve's open and close in there normal cycle .
joe martin, July 2009
cheers for that

joe martin, July 2009
This is correct - it's the compression release mechanism. At running speed, the exhaust valve stays closed and the engine runs at full compression.

Without it, the engine would be almost impossible to start with a recol starter.

phil_saunders(a)bigfoot.com

Phil Saunders, July 2009
link Click here to see other fixes for Mountfield.