OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Suffolk motor

I got my qualcast going it was running good till I frantically turned it off cos it threw a apart out the muffler but it floated a but in the air so do you guys think it could of been dirt in the muffler cos it's sat for so long? Or something much worse like a valve?

sorry but its not real clear what your sayin there.


It was running and something flew out the exhaust.
And it floated.


Did it clunk and bang??
Does the motor turn over fine???


Could have just been a bit of carbon or something.

Could have been a piece of cloth someone had stuck in there to keep the rain out, who knows? I suggest you go through a rudimentary "safe to run" check on the engine. Disconnect spark plug and crank it slowly, to see if there is any resistance at some point in the rotation, or any odd noises. Turn it backwards as well as forwards. If all seems well, crank it faster. If it still seems OK, feel the compression specifically - most valve gear problems will cause an obnormality there. Look for oil leaks and check oil level. Check that it has fuel and the fuel is not going anywhere it shouldn't - not leaking or flooding. Then, reconnect the spark plug, start it, and run it at idle for a while. If it sounds good and runs properly, increase the speed a bit, with no load. Don't get carried away with the speed - I'm not sure it has a governor. If it is still running smoothly with no smoke or odd noises, try applying some load (i.e. mow a bit).

Threw a spark out the side sorry auto correct made it into apart! It seems to turn over ok still thought it might be an exhaust valve doing something wrong

We can't assess the condition of the exhaust valve without either doing a compression test or removing the cylinder head and inspecting the valves. If you were doing the latter you would lap them so you knew they were sealing properly. Normally, though, even if the exhaust valve threw off a spark, it wouldn't make it through the muffler. Most likely any spark that comes out from the exhaust pipe was generated in the muffler, by burning old carbon. However if you are going to run that old engine under load, it should be checked out first.

That begins wth some form of compression test. Preferably, use a pressure gauge with a non-return valve so it retains the maximum reading, and hold it against the spark plug hole while cranking the engine rapidly, with the throttle wide open. If the pressure is less than 100 psi, you should then put a spoonful of engine oil in through the plug hole and repeat the test. If it doesn't increase to perhaps 120 psi, you would need to remove the head and lap the valves. If it does increase to a decent figure, the valves probably are in reasonable shape, but the rings are worn out.

I would say if its been sitting a long while the carbon/coke build up looses its adhesion to the inside of the head and muffler etc. It either dries out or it oils up then it all gets blown out the exhaust when you run the motor next.


If the mixture is a bit lean this will make the carbon burn off as well.


I get the same sparks thing with a lot of the older (60's & 70's) 4 strokes i fix up. Even after setting the valve clearances and de-cokeing the head and piston they can still blow sparks. Carbon in the muffler, definately more prone to doing it with a lean mixture.

No question the exhaust gas temperature is higher when they are lean, Bob, and that heats up the valve and the muffler. A healthy muffler doesn't really have anything in it to burn unless it is on a 2 stroke, and there is probably no such thing as a healthy muffler on a mixed-fuel 2 stroke unless it's always run flat out. However we just don't know if Michael's ancient engine is healthy or not. He could have a gummed up carburetor resulting in lean mixture, he could have worn out rings leading to a carboned-up combustion chamber and muffler, or he could have gunk on his exhaust valve causing it to not seal properly.

Ok got it going and mowing just need a new exhaust gasket it's a fibre washer where would I find one?

I estimate that there are probably about ten of those engines in Australia Michael, and all of them are about as old as yours. The way you get a gasket for it is to buy some exhaust gasket material from Repco or someone similar, mark it up to match your muffler flange, and commence cutting.

I know someone who has not only bought one but has two full engine kits, I just googled "suffolk 75cc gaskets" and found several useful links.