OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines B&S Quantam motor

I had this motor running and starting very easily a couple of days ago and all of a sudden I can't get it started or even attempt to start. I normally wouldn't bother too much with it but it was running so well. I have tried everything I can think of and not a peep out of it. Any thoughts as it is annoying me?

Hi Norm,

When they run one minute then won't start for me usually it's one of the following ,spark plug ,coil ,kill switch wire earthing,
sometimes the fuel hose perishes on the inside and drops small particles of rubber that blocks the carby or the choke / throttle
linkage fails to work correctly. Occasionally a bolt or bolts etc can come loose stopping it running like when the flywheel nut
is loose and the key breaks throwing out the timing.


Cheers
Max.

Hi Max,
All of the above have been checked, new plug, can't get a peep out of it even with starter fluid. I haven't pulled the fanwheel yet but it is giving no sign of kickback as I would expect if the timing had moved. Throttle linkages all fine, coil has been changed, got me stumped, it was running so well. Got me stumped

Hi Norm ,

I once had to change the coil 4 times until I found a good one ,when you don't have a coil load tester it's worth
taking a coil from a mower that you have just run a minute ago to save time , it's the same thing with a spark plug I'd rather
use a plug that runs in another mower just in case the new plug doesn't work .

I've had some run then next time won't start and when I check the magnet on the flywheel they have lost
their magnetism.

sometimes I put starter fluid in the spark plug hole instead of the carby as that will tell if you have a valve or cam problem
or a flooding problem.

I usually start with a compression tester and do the easiest things first then later on check the flywheel key just in case the
flywheel has moved a lot and the motor has no kick back.

Cheers
max.

Yes Max,
The coils I use I know have come off a running motor and my tester says I have spark. ( actually this was part of the problem when I went to test for spark I had none but after swapping coils around I discovered the LED in my test light had blown, I had lasted a while) Fitted another LEd and then I was able to test for spark again. I usually test with the plug that is in it, then another from my box of plugs and then with a new one. I figure one out of the 3 has to be ok. The only thing I haven't done to this motor is pull the fanwheel which I will do tomorrow

If I remember correctly the Quantums are side valve engines. Have you checked for either a sticking valve or if the valve have made to near zero clearance?

Hi AVB,
I haven't checked the valves but compression feels the same, just so strange to go from a good running motor to nothing
Just checked and keyway on fanwheel lines up with the crank so timing hasn't moved. Think it is time to ditch this motor

I got it running, played with so much on this motor I'm not really sure but I think it was an issue with the primer, they are a dog of a setup. I just don't understand why it was working so well to suddenly refuse to start. Anyway all is well that ends well even though I spent a lot of time on it

Now it has one those air filter base mounted primers those filter bases do tend to warp requiring a wedge gasket to be made up. And easy to warp them by over tightening the mounting screws and from excessive heat and aging plastic.

Yes AVB,
That is a pretty rubbish setup and yes I fitted another filter base and the old one went straight in the bin. What threw me here was I thought the primer was anot working but I couldn't get a peep out of the motor with a squirt of starter fluid down the throat of the carby. I ended up putting a squirt into the manifold with the carby off and it fired so that proved it was a carby issue