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Collection, Preservation and Display of Old Lawn Mowers

Villiers mark 10 no speed control


I finally got the MK10 running after using an in line spark tester and finding out it had a good spark after all and the only issue was a blocked jet... Only issue now is that it 'runs away'. It starts first pull from cold every time but once started gets faster and faster until I have to pull the HT cap off of the plug to stop it. The governor is engaging but even when it fully closes the butterfly, it keeps getting faster. The only thing I can think of is that there is an air leak somewhere but I've changed all the gaskets and put a good layer of gasket sealant onto them too.

Any ideas would be greatly appreciated,



wristpin Fri, 29/04/2016

Can't quite get my head around that. Unlike a diesel it wont be running on overfilled sump or air cleaner oil!

Not doubting your sanity but are you sure that the throttle butterfly is working correctly  - any possibility of a full rotation causing the governor to open it rather than close it?

I think that if it is a bad air leak the engine would just run out of "steam" and be a pig to start. I'm not a great fan of gasket goo especially on new gaskets ; so long as all flanges are true it should not be necessary and excess goo may lead to other problems . If I'm reusing a gasket on good flanges (needs must!) I'll sometimes put a smear of grease on it.

Keep us posted when you solve it - never too late to learn!