Hello Adrian:
I suggested a fuel problem but you seem to have eliminated the possibility.
The only other way I can think of fuel starvation would be a blockage in
the line from the tank which restricts flow at higher speeds. The carbs
could be starving for fuel but you won't find it once the engine slows down
and the pump catches up. One suggestion would be to run the car flat out
to the point where it won't rev, then declutch, shut off the engine, stop
the car, and check the level in the float bowls.
Your changing the distributor suggests that the problem is not there. Have
you considered the possibility that the timing chain may have jumped a
tooth. This could happen if the chain is old and stretched. The only
other thing I can think of is valve seat recession which would cause the
tappet gap to close up to the point where the valves are staying open.
This might be the cause of the backfiring. Let us know what you find.
John McEwen
>Well Folks,
> First off, thanks for responding. The situation is as before - I
>can't get my Midget over 3500rpm. It just won't go fast and it starts back
>firing in the exhaust. It seems to run fine at idle and just before I hit
>3500rpm.
>I done the following, to no avail:
>FUEL:
>Removed air and fuel filter.
>Installed new electronic fuel pump.
>Checked float height, Grose jet operation, choke operation.
>Checked for manifold/spacer leaks with carb spray.
>Fuel in both reservoirs is clean and about the right height.
>Checked fuel line between carbs
>"Pistons" move up and down smoothly
>Fuel is not old, as this is my regular driver.
>Tried various mixtures (raising/lowering jets)
>
>IGNITION:
>Replaced CB points, condenser, rotor, plugs.
>Swapped with old but good distributor, distributor cap, plug leads.
>Rechecked timing and dwell.
>
>MECHANICAL
>Checked compression - 140 +/- on all cylinders.
>
>All I can do now is rebuild the carbs and recheck the valve clearances
>(they were spot on a couple of months ago)
>
>Any other ideas. I'm at the point of taking it to my mechanic but he knows
>even less than me about MGs, which is scary.
>
>TIA, Adrian
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