MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Sputtering acceleration

This problem won'y go away. The acceleration sputters for a second after upshifting at high RPM, indicative of low oil in carb (HS4) dashpots, or too light oil in dashpots. But I've tried everything from 3in1, 20w, 30w, 50w, and ATF with the same effect. This is an acquired problem (didn't used to do it). Any suggestions.
thanks,Tyler
TYLER

Tyler,
It is common for the inside of the vacuum chambers to get dirty above the normal travel range of the carb pistons. Especially if air filters are neglected or gaskets are omitted. This causes the pistons to hang up erraticly on full throttle - high rpm excursions, causing the mixture to go off. Depending on how they stick, it can be rich, lean, or both in alternating random manner. If severe, it can temporarily foul or overheat plugs, sometimes taking a couple of miles of "normal" driving to clear. Similar things happen to motorcycles with sticky carb slides. Yours sounds as if the pistons are hanging in the max up position briefly, giving lean mixture until they fall down to the correct vacuum determined postion.
Remove the vac chambers and clean carefully with carb cleaner, lacquer thinner, etc - NO ABRASIVES! Do a drop test on the piston/chamber sets. They are matched sets, and despite the 50/50 probabilities, I find that something like 75% have had pistons switched in their chambers.
FRM
FR Millmore

FR,
Thanks. Your explanation sounds most probable. I don't think it's electrical related. I'll tear into the pistons to find the problem.
Tyler
TYLER

Just a thought Tyler, but check your vacum lines for splits etc. as well,
happy motoring.
jim.
J A Kelly

This thread was discussed between 10/10/2005 and 12/10/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.