I've got the same problem. My local mender says "ha ha - said you shouldn't have bought it" However, he reckons that if you've maxed out the adjustment on the foot pedal, you're going to have to face up to some big bills. That's if you can find anyone to do it - and get the parts for this obsolete machine.
Sorry.
Simon
November 2010
I can answer this question...
How can I fix my 15/40 hayter heritage hydrostatic drive lawn mower?
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix lawn mowers.