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MG Midget and Sprite Technical - learned all about technique for adjusting valves

I have decided that putting the car in 4th gear and pulling it while watching the valves move is a fine way to adjust valves (you can see when to stop). I found that all of mine were too tight (by about 1-2 thousandths). I did get a few looks from passers by as I was crouching in front of the car pulling while sighting down the valve train. While I was at it I also determined that my static ignition timing was about right and that my timing mark is in the correct location. I used my multi meter continuity beep to hear when the points were opening.

See more pictures:
http://www.pangalacticconsortium.com/cars/MG_midget//index012.html

I had to remove my carburetors (AGAIN) more time (float valves sticking for some reason).
Is sticking float valves a common problem on SU carbs?

I think that I am getting reasonably good at adjusting the carbs now. It is actually kind of fun.

Rebecca
R Harvey

Nice one Rebecca. I use that method to do my tappets because, as you mentioned, you can see exactly where to stop to make the adjustment, using the rule of nine, ie. when number 2 valve is open adjust number 7 valve, 1 open, adjust 8 etc.
Yes the float (needle) valves on SUs do stick. You can overcome the problem by buying a kit which contains the needle valve and seat. Easy to fit too.

Bernie.
b higginson

You need a filter in the fuel line to stop crud from the tank blocking or more likely holding float valves open.

A
Anthony Cutler

>>> Is sticking float valves a common problem on SU carbs? <<<

>>> You need a filter in the fuel line to stop crud from the tank blocking or more likely holding float valves open. <<<

Funny, I've been through this with my Zenith carb. The first time it stuck open, I'm positive that my fitting of a Grose Jet was the cause. (Sorry to flog that old horse again - I've mentioned it regularly in the past). As I result, I went back to the original type of valve, and it's worked great for years. I also fitted TWO clear inline fuel filters, one right at the pump (mechanical pump in the 1500), and another at the carb.

I mention all of this to say that my car showed symptoms of overflow just the other day (deteriorating idle and stalling, plus fuel in the forward charcoal canister), and lo and behold, it was indeed overfilling again. I disassembled the ZS, and even though the float chamber was spotless thanks to the filters, and the float valve was free to rattle, and worked well when I tested it by blowing through it and pushing the pin, it had still overflowed somehow. Yes, the float is good and has full travel...

So I don't know. I attended to the valve with carb cleaner and compressed air, and I hope to get the carb reinstalled this evening. We'll see what happens. Just another little mystery, I guess. Ain't it fun.

;-)

-:G:-
Gryf Ketcherside

I have a filter. I could not find any crud. My fuel lines and my fuel tank are new (but I did not replace the float valves yet). It is a clear type so that I can see how nice and clean the fuel is.

Rebecca
R Harvey

This thread was discussed between 10/08/2010 and 11/08/2010

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.