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MG MGA - Setting idle

The idle on my 1959 MGA 1500 is way to high. How do I set it to a lower rpm?
david kirkpatrick

Hi David

The two carbs are linked with a connecting rod. You should release the rod by loosening the clamping bolt on the rod, so the two carbs can work independently. You can then adjust the idle screw on each carburettor, but you should also check they balance.

I would suggest you take a look on the web as there is lots there - such as this John Twist video https://www.youtube.com/watch?v=4nvGLgO6pj0

Graham V

Graham

Adjusting the idle by disconnecting that rod will definitely upset the balance. If the carbs are already in balance that rod should never be disconnected. Idle adjustment is simply done with the rod connected and adjusting the idle screw with a screw driver.

Steve
Steve Gyles

Hi Steve
Yes of curse you are right, but in my defence, I did say the balance would need to be checked.
And in practice, I wouldn't do it without undoing the rod and checking the balance, as it only takes a minute or two.

But in fact if David doesnt touch the connecting rod, I guess he would actually need to adjust both the idle screws by the same amount

Graham
Graham V

Graham

I screw one a turn out of the way while I make the idle adjustment with the other. Then bring it back to make light contact against the stop. Flick the throttle cable a few times to check all is well, then job done.

Steve
Steve Gyles

check the high speed idle cam that brings up the idle speed when you lower the jets for starting
S E Bryan

Thanks for the advice. It appears that the springs do not have enough tension. How does one tighten the spring? An auxiliary spring looks like a viable solution.
david kirkpatrick

Each carb should have a torsion spring on the outboard end of the shaft. Loosen the clamp screw, rotate the clamp to wind up the spring to be tighter, and tighten the screw.

There should also be a tension spring from the end of the throttle input arm (also end of the throttle cable) to a bracket that is attached to lower bolt of rear carb mount.
barneymg

This thread was discussed between 09/10/2015 and 11/10/2015

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