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MG MGA - Throttle cable and choke linkage adjustments

Question #1: When the accelerator pedal is fully depressed should the throttle shaft in the carbs be fully open (touching the throttle stop tab.) I've assumed this is the case but there isn't enough cable movement from the accelerator pedal travel to pull the cable through the total travel available at the throttle shaft. I have about 90%, or in other words there is 10% more movement to go. I know that the cable attachment arm on the throttle shaft is adjustable but when adjusted for full throttle opening the butterfly will not close completely when the accelerator pedal is released as it needs more cable travel to close completely. I feel I'm overlooking and obvious solution.

A note about the choke linkage adjustment as I've never seen this mentioned and when out of adjustment it resulted in a rich mixture to the rear SU carb on my MGA. I had what I assumed to be a sticking jet bearing assembly on the rear carb. After using the choke the rear carb jet would not return fully to the upper position resulting in a partial choke and rich mixture on the rear carb. I would have to manually push the jet to the closed position as the return spring wasn't strong enough. I assumed that I would need to rebuild the jet bearing as it appeared the seals were binding, but once the carb was off the motor the jet bearing moved smoothly. The culprit was the adjustable link between the two brass choke arms. The link needs to be adjusted to the correct length so it fits easily between the choke arms with a slight amount of free play within the choke arm connections. In my case it was slightly too long and as a result held the rear jet bearing in a slight open choke position resulting in a rich mixture for the rear carb. -M.S.
Martin Straka

Martin, just checked my 1500, and yes, the throttle opens fully. There is a little bit less than 90 degrees of turn on the butterfly spindle, and about 3 inches of travel measured at the throttle pedal. There is an adjustable stop on the throttle pedal, have you got it adjusted too high?
Lindsay Sampford

Lindsay,

Thanks for your information. I assume that the throttle stop is adjusted with the carb off the motor to visually see when the butterfly is parallel with the carburetor bore. -M.S.
Martin Straka

Martin, I don't think the throttle butterfly can go any further than fully open, and the throttle pedal stop (down on the toeboard beneath the pedal) is simply there to stop the throttle cable from being strained too much when you floor it, I may be wrong. I wouldn't bother removing the carb, just get someone to push the pedal all the way down, then see if you can turn the spindle any further. If you can, you need more travel. Also, make sure that your cable can move freely in its outer, sometimes a strand of the inner cable breaks and restricts the travel.
Lindsay Sampford

See here:
http://mgaguru.com/mgtech/carbs/cb114.htm
http://mgaguru.com/mgtech/carbs/cb115.htm
Barney Gaylord

Thanks for that Barney. Checked mine out and it was a right mess! All set up properly now.
Lindsay Sampford

This thread was discussed between 06/07/2010 and 08/07/2010

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