Its much more common for engines to spit back through the air cleaner, due to a weak mixture or whatever, but through the exhaust is unusual! An explosion in the exhaust when the ignition is turned off isn't a worry though.
I'd replace the plug, and check that the silencer isn't loose. Which machine do you have?
John
Many thanks John. On reflection I think the spit comes from the air cleaner, I just assumed it was the exhaust.
The machine was purchased from Homebase...Sovereign XSZ40, does the job well, am just not used to being spat at from an engine!
For sure, engines spitting back through the induction system is always due to a weak mixture somewhere along the line......not too helpful as the fast running speed mixture is actually fixed by the main jet size.
It may be possible to richen the slow running mixture by turning the idle jet screw (if there is one) 1/4 turn anticlockwise, otherwise there could be a tiny air leak somewhere.
I'd still try a new plug though, even if the machine starts well.
John
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local