its a modern day 3 1/2 hp classic engine with pretty plastic bits . grounded heavy smashes the powerdrive pully blade spacer . i have however replaced the damaged bits .but the machine is hyraulicing when you pull the cord ( a term i am aware of as a vehicle fitter ) it rips the cord from your fingers as it atempts to fire . oil level is ok , i suspect a timing issue possibly as i am aware they have aluminium woodrift keys intended to break in the event of a ground strike ? with the plug out it turns freely , i have checked the 2 i am aware of flywheel and the steel key on the main shaft . excuse the random order of events just putting all the facts i can remember

steve, October 2012

Only 2 things can cause this - either the blade assembly is loose on the shaft, or the flywheel key is sheared, allowing the flywheel to rotate relative to the crank. If this has happened, it will have the effect of advancing the ignition timing, causing the effect you describe.

You will have to REMOVE the flywheel to check - just looking at the top of the key through the slot that is visible when you remove the nut/washer will not show if it's broken. It will be TIGHT on the shaft - even if it has moved.

phil_saunders(a)bigfoot.com

Phil Saunders, October 2012