20-05-2018, 06:51 PM
(20-05-2018, 07:53 AM)Dave Wortley Wrote: Yesterday I did a 75 mile run in the chummy. It was a hot day.All was well for the first 30 miles but then the engine started running very lumpily and would not exceed 25mph in 2nd gear for a further 20 miles. On climbing out of lower ground onto the moors above Sheffield everything returned to normal. The same thing happened two years ago on the same run so I fitted a heat shield on the exhaust manifold and on the downpipe but these mods haven't done the trick. I checked and cleaned the distributor points,ap and all HT lead connections but all appear sound anyway. Any ideas re preventing this please? The chummy has a 4 blade fan and small SU carb and electric pump. Looked on the old forum but can't find anything.Presumably with the SU you are using a later type manifold. As I said in another post recently, I have found it helpful to cut through the hotspot. It was there to help vaporise old fashioned petrol, but it's more of a hindrance with today's product. The other thing which can help is winding the exhaust from the flange down to a point beyond the carburettor with the modern equivalent of asbestos tape.
Thanks,
Dave.
Robert Leigh