MG Car Repair: A series engine starting problems, temp guage, morris marina


Question
Hi my car is actually a Morris Marina, but the same A-series engine etc as in
the MG Midget.   My carburettor (SU) is very worn apparently so I've got a new
one coming but its going to be 2 or 3 months...

When starting the car it doesnt like the choke to be used otherwise it will just
cut out.   I have to start it so it kinda fires on one cylinder and let it shake and
judder until the temp guage hits the normal position (30ish minutes) where it
suddenly starts to fire properly.  If the throttle is touched at all in that time it
cuts out then struggles to restart.   Once the engine is run it seems to run
after a few initial backfires and pops,  all day.   But then morning comes...

A garage tuned the carb and set everything perfectly but warned me that
around the 2000rpm position on the needle wasnt to healthy so best get a
new carb.

So whats making it a nightmare to start?   How can I help it?

Answer
Hi James, the choke of an SU is not a choke but it just loweres the jet in relation to the needle. It is very rare to need a new SU carb. The jet and needle are replacable and the butterfly shaft can be replaced and the case bushed.
You need to start from scratch and do a compression test (wet and dry) then check valve adjustment and ignition timing. AFTER you do that and confirm the engine is good, you can work with the carburetor. The carburetor is adjusted by the reactions you get when lifting the small pin on the under side of the the top pot and if anything is not correct on the engine you can not get a correct carb adjustment. Let me know the results of the wet and dry compression tests and the ignition timing and I will walk you through the adjustment of the carb.
Howard