Unleaded midget "run on"

Seems like there is a still a hot spot problem in the combustion chamber reshaping or polishing the chambers does help. (and quite common)

Mine has the same problem. I stop the engine using the clutch.

Peter...

I have a MGA 1600 Mk II, which I have driven since 1962. I used to have that problem all the time...especially with the high compression head. Unless I could get fuel with an Octane of over 100, it "ran on" all the time. I got in the habit of dumping the clutch in 4th gear to stop it.

I've since lowered the compression ratio, and the problem has mostly disappeared...along with the horsepower, I might add.

I recall that the problem was worst when the car had been run at low RPM for quite awhile. I think the combustion chamber got fouled with carbon, which caused ignition after shut-off. You might try a slightly hotter plug, but keep it within the range of acceptable operating specs.

The cheapest solution is dumping the clutch. If you are an MG driver, you must have a high tolerance for these idiosyncrasies...otherwise they will drive you nuts.

John

I have has same problems with an MGA, and a TF1250.

I got into the habit of just easing off the clutch pedal in 4th gear as I turned the key off.

Ian F

somehow - basically a valve is opened when the ignition is turned off. BTW my 1970 AH Sprite also runs on on occassion.

Neil

Just a cautionary note on this,

our midget used to run on something cruel ( not unleaded) and we wound up with a head gasket going south during a drive. since I put in the new head gasket, we have had no problems with run on at all.

I use the we as it is meant to be her indoors car ..........