Mountfield 4155H not turning over on start

Hi , intermitently my Mountfield 4155H (same as Stiga Park) has not been turning over on the key , it will do about half a an engine turn on each turn off the key, but not enough to start the engine. Symptom is like a weak battery. Previously I've been able to solve the problem by loosening and retightening the battery connectoions, but today that makes no difference. Have also tried a fresh fully charged battery but gain that makes no difference. Any ideas out there ?

I would check your valve lash settings. Briggs engines are usually .003-005" on intake valves. .005-.007" on Exhaust valves. If you aren't familiar with setting valves, there are a lot of good videos on youtube explaining this procedure.

sorted, seems like it was simply a bad earth

If tightening the connections help, you probably need to clean them. Glad to hear you're working. BTW, that's a wild looking machine.

battery connections are fine and clean . Started playing up again today and not turning over more than about half a an engine turn on each turn off the key when trying to start it. Symptom is like a weak battery. Last week when I put it away it was turning over on the starter no problem, . Today even with a fresh fully charged battery it would only turn over about half an engine turn on each turn of the key . Eventually got it started today by giving it a hand by hand spinning the top of the engine. Seems now like it starts okay when the engine is warm, but doesn't turn over more than about half an engine turn after being left sitting for a week or more

Check the oil, smell it for gas. If needle valve is leaking you could be getting hydrolock. If you smell gas, need to clean carb and test to see if valve seals. Change oil before running.

oil was changed at start of summer, no smell of gas

No smell now, or start of summer?

no , no smell now or at start of summer....but looking at youtube, the symptoms are very like those for a hydrolock. It has a fuel tap below the fuel tank so i'll close that till next time i use it and see if that makes a difference

Like Wood said check the valve lash