Engine Races on Startup


Asked by TomKr43 Aug 28, 2020 at 02:50 PM about the 1970 MG MGB

Question type: Maintenance & Repair

Prior to work car ran perfectly with new exhaust but leak at manifold.  I
removed the twin SU carbs (new 30,000 miles ago) and manifolds a couple
of weeks ago to replace the exhaust manifold (stripped studs).  Since
pollution control was removed years ago I decided to go with the earlier
intake manifold which appears to be in good condition.  Reassembled using
gasket sealer only on the manifolds.  All additional gaskets all accounted for.  
Reassembled all and have double checked throttle linkage and vacuum lines
and can find no issue there.  Oil had leaked from carb dampers on the bench
so replenished.  Starting the engine it immediately jumps to 3,000 rpm
before I can shut it off.   

4 Answers

How to adjust SU carbs. http://www.sucarbs.com/?page_id=20

1 people found this helpful.

Thanks for the link. I revisited the situation to see if idle screws were touching their stops and they were not. The rear shaft between the two carbs was not installed correctly as actuating tab was behind the carburetor it should have been in front of. Loosened front carb enough to correct the situation and engine is back to normal.

1 people found this helpful.

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