Chicagoland MG Club
Adjusting Your MGA Choke
Mixture adjustment and synchronisation of SUs seem to be widely understood. Of equal importance is the adjustment of the choke mechanism. If set too rich, the choke will fill the cylinders with raw fuel and dilute the engine oil causing premature bearing, piston ring and cylinder wear. If set too lean, the car starts hard, which drains the battery and overheats the owner.
Of first consideration is the fit of the clevis pins in the choke levers. If these holds are worn larger than the pins, the chokes will not operate through their entire range. New levers and clevis pins are the cure for this problem.
Once the new parts are fitted, adjust the slack out of the choke linkage at the interconnector link. Slacken the top and bottom nut so the linkage is "relaxed", then tighten the bottom nut so that just a bit of pressure is brought to bear on the lever. Do not overcompensate, as this will "pre-load" the chokes and cause over-rich mixtures. Once set to your satisfaction, run the top nut down on the fitting to lock the adjustment. You may want to use an extra nut on the bottom as a lock nut. Now, hook up the choke cable. Give it a turn to the right to help the cable lock work, and don't get the cable too tight; leave a little slack.
The choke cam may be adjusted to suit weather conditions by moving the link rod to the appropriate hole. #1 opens the butterfly a small amount slowly, #3 opens it a large amount quickly. #3 is intended for colder weather, #1 for warmer climes. Yours may be set at #2 where the majority were set to begin with. If so, you may want to leave it alone, as the #2 setting seems to work in just about any climate.
The choke adjusting screws should be set last of all, and should be backed off completely when setting the idle, and synchronizing the carburetors.
Set the screws equally so they are just shy of the cam, about 1/32". Smear a dab of light grease on the cam face. If the chokes and idle screws do not hold their settings, new tension springs may be in order.
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