Surging Lawnmower

[Burnerman]

Here’s a wee test.
Hold the governor rod by hand, so the engine runs slowly. If it tends to stall, screw in the idle screw to keep it running.
If all is well here the engine will continue to run with no issues.
Then, hold the engine at high speed, using the governor rod. ( you’ll feel the rod trying to fight you here).
If the engine is short on fuel, it will tend to splutter and fail.
John

 

[WhoMe?]

may not be helpful
but have you replaced all the fuel from last year
are you using E5 / 95% 97% or E10 ???
unlikely but thought i would perhaps mention .....

Yes, last weekend when the issue started. Before that it was a couple weeks old

'The bit at the bottom', probably. The weights are flung out, under centrifugal force, which then closes throttle. The surging, and the video suggests that there is an issue of sticking governor.

Is that nut at the bottom left of your photo done up tightly to prevent the mechanism from moving on the shaft?

Thanks both, I'll take a look

 

[WhoMe?]

Here’s a wee test.
Hold the governor rod by hand, so the engine runs slowly. If it tends to stall, screw in the idle screw to keep it running.
If all is well here the engine will continue to run with no issues.
Then, hold the engine at high speed, using the governor rod. ( you’ll feel the rod trying to fight you here).
If the engine is short on fuel, it will tend to splutter and fail.
John

I did this. Hold it one way it stalls, the other way it fights me and revs high

 

[Burnerman]

If the engine stalls when it’s trying to run at low speed......
Turn the tick over screw clockwise to keep the throttle open;
If it still stalls, it’s a pilot jet blockage or adjustment required. Some are adjustable, some are not and we’ll need a picture or two of the carb to sort that one.
Interesting, this one or you may not agree!
John

 

[WhoMe?]

Thanks for all your advice. I'll have to find some time this week between work to take a look

 

[Burnerman]

Stick with the diynot heroes and we’ll get there.....

Probably!

John

 

[WhoMe?]

Thank you, I just hope I've not done something stupid