Kitchen Garden Forum

Are you out there Clive?
My rotary mower with a B&S Quantum 40 engine has recently developed an alarming kickback when I try to start it. It will eventually start up and run quite well so I can still use it.
Searching for this problem on the web, it came up with either dodgy valves or a slipped flywheel. I don't remember whacking anything while mowing which might have moved the flywheel.
Can anyone help? Is it easy to check the flywheel which I presume is the bit with the air vanes on it under the starter mechanism?

John

My partner suggests you might be pulling the starter too hard, causing it to recoil, try pulling smoothly for the full length of the cord. Sounds like your engine is running OK.

Hello John,
Sometimes a slightly loose blade and/or damaged blade mounting can lead to a most violent kick back...
I remember one such on an old Mountfield M4...nearly took your fingers off as the rope handle snatched back.. .

..Also with ref to fingers etc....take spark plug lead off and earth it before investigating blade...same with the flywheel end of things...and if in any doubt of your own abilities entrust it to a local service agent. Do I sound like a worrier.?....er, yes I am

..and put the lead back on after..!!

Clive.

Thank you both for your replies. I took the blade off a couple of weeks ago to sharpen it. After your comments Clive, I think I had better check that I have got the blade back properly!

John

I was just wondering, if you have ground one side of the blade more than the other, John, whether the blade is out of balance, maybe this could cause the problem.

Thanks OH
I think some serious blade checking is needed this weekend.

John

Deleted

Dear John,
sometimes there is nothing actually wrong with the machine but the engine is just at the wrong point in the four stroke cycle when you start to pull and it goes the wrong way. This can either result in the machine backfiring or snatching the pull cord out of your hand. It mostly occurs on older engines as they become worn or if you pull the cord too slowly.
The easiest way to reduce the incidence of this is to slowly and gently pull the cord (you are not trying to start the engine at this point just moving the piston to the correct start position) until you can feel the pressure building up within the engine. You then allow the cord to wind back into the starter housing and then pull firmly.
Of course this will not cure the problem but will reduce the incidence of it occurring. Try not to have too firm a hold on the pull cord as it is a lot less painful to have it snatch your of your hand rather than yanking your shoulder to pieces. I have three machines which do this to me and all are older machines. One a four stroke cylinder, one a four stroke rotary and two stroke hover mower. All are very well maintained but have simply got slack inside and there is not a lot that can be done to rectify this.
regards Sally Wright.