B40 stops after 5 mins and won’t start again.

[Bees]

Persistance will pay off.

This type of problem are so frustrating. I have always felt diagnosing a problem is the real skill of a mechanic. Once the fault is found sorting it is compartively easy.

It could be many things.I would try replacement parts if you can, for example the coil might be fine on the bench but breakdown in use. Same with all electrical parts.


Have you checked valve clearancrs to eliminate them?

[Hancock]

No I haven't ,it is frustrating . I have a feeling it's the spark breaking down. I'm going to get a couple of new ones set the gap.when the bike stops and won't start I'll put the new plug in see what happens, I'm no mechanic so takes me a lot longer.
Thanks for help

[Bees]

Its all part of the charm of owning old bikes!

My hunch is electrical. Its a process if elimination. Change 1 thing at a time. I'd try the coil if its not the plug.

Checking valve clearances doesnt cost any money just time.

It could be fuel flow. Next time it happens press the tickler to see if the float bowl is full or empty.

Does it start easily once it has cooled down?

You'll crack it soon. Then you get the grin factor that is also part of the charm if fettling with these things.

[MICKREEVES]

can you get good flow from the carb when you disconect from the carb
Mick