Does anyone know how to replace the timing belt on my Honda gvc 135 lawn mower engine? I have removed engine from mower and opened rocker cover, and also removed cam-belt top sprocket.

It looks as if I must split motor casing around the bottom end to be able to thread belt around bottom sprocket. What about the timing of the valves? I have no manual, so any advice would be very much appreciated.

Stephen Roderick, May 2008

Thanks Highrange and John for your prompt reply. I have found the timing marks on the top sprocket. I am in the middle of making a simple puller to remove the alloy bottom casing as it looks a bit fragile, and there are 2 studs and a crank bearing which has to slip off with it. I agree a book would be a good investment.

Stephen Roderick, May 2008

Yes, the latest Haynes Mower manual does cover this engine. As I recall, you need to split the crankcase to slip the belt onto the crank pulley, set crank to TDC, and then remove the camshaft spindle to pass it over the cam pulley. Refit the spindle. The cam pulley has marks to align with the top face of the head, at TDC... set both camshaft and crank to TDC, and then slip the belt into place..... but check the book!

Highrange, May 2008

I think you will have to split the bottom of the motor to replace the timing chain.....sorry I can't help with the timing mark alignment but they will be punched onto the sprockets. However, Haynes do a Lawnmower repair manual which covers this engine - it could be an essential buy here.

John, May 2008