10 replies to this topic

[Mutley001]

Hi all - hoping someone can help
I have a very specific issue that I just don’t know whether to start with:
My 1275 A+ Mini has starts and drives fine from cold - no issue at all.
However - if after driving I park up for say 20 mins and switch off it will start up again fine but as I push the throttle to pull away the engine revs die and it stalls, it will do this 2 or 3 times unless I rev the nuts off it! then after a few minutes it runs absolutely fine again.
Anyone any ideas?
Thanks in advance!

Edited by Mutley001, 24 January 2025 - 03:28 PM.

[sonscar]

It is possible that the float is letting fuel into the engine and flooding it,Steve..

[alpder]

Manual choke, or automatic?

[timmy850]

I’d do all the usual checks:
Make sure the dashpot oil is topped up
Make sure the piston rises smoothly up and down
Check there are no air leaks on the manifold or breather ports
Check the air and fuel filters are in good condition
Check the choke mechanism is fully returning closed when you push the cable in

Next time it happens I’d also be tempted to remove the spark plugs and see if they are black/covered in fuel and misfiring

[bpirie1000]

Think it is a mixture issue.

Is the driving normally fine. No flat spots?

Is it a 1.3/4" carb?

[Mutley001]

Yes all driving normally other than the issue described.
All good with the carb as far as I can tell - dashpot has oil, piston smooth, no air leaks, just had new air and fuel filter along with new fuel pump.
Choke (manual) seems fine and returns normally
Any other thoughts?

[BobbyMax]

Check inline fule filter isn't gunked up

[andyapanel]

Have you tried increasing the idle speed?
I had a similar problem on my RSP; eventually, I found the idle screw had decided to change itself.

[coopertaz]

was it fine before you had the filters renewed? if so start problem with parts fitted. have you got heat shield fitted to carb or re-routed fuel feed closer to exhaust when doing work could be fuel vapourisation whilst parked up.

[Mr Piggy]

What's the new fuel pump you fitted? The original SU pumps produce about 2 or 3 psi, ideal for SU carbs. Some non standard pumps produce 5 or 6 psi and need a pressure regulator or the pressure can overcome the float needle valve and flood the carb causing an over rich mixture. Maybe ok when the engine is cold and when running and using fuel but when parked up hot, will gradually flood the carb.

[Mutley001]

Mr Piggy - right on the money - thank you!
Fitted a fuel pressure regulator set to 3 psi and the issue is now sorted - thanks very much!