QuestionQUESTION: Hi, Engine serviced with new everything incl leads, points, condenser etc, timing set correctly. SUs have new butterfly shafts fitted..no leaks. Car idles roughly. I have tuned the carbs by usual method..ie 2 turns in the jet and start from there. No problems except that the car idles smoothly with the crankcase breather pipe disconnected from the manifold. As soon as I reconnect the pipes to the carbs idle gets rough. Any ideas?
ANSWER: Hi Roger. Are you sure you have connected everything correctly? The breather pipes should go from the crankcase breather to both carbs, not to the manifold. Do you have the earlier system with a flat circular valve on top of the manifold? They often cause problems if the internal diaphragm has split or perished.
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QUESTION: Hi. Its the later one where the pipes go to the carbs. What would happen if I left it off?
Thanks
AnswerHi Roger. You cannot tune the carbs with the pipes disconnected. If you leave the pipes off, excess air will be sucked into the carbs producing a weak mixture, which could lead to engine overheating, burnt pistons & burnt valves.
If you tune the carbs without the pipes and then connect them, you will get a rich mixture.
Have you cleaned the wire gauze air intake filter situated inside the oil filler cap? If it is blocked, this can cause rough running. Wash the cap out with petrol (gasoline) and dry it.
If the problem persists, please give me a description of the rough running. Is it a splashy uneven sound, or is it a rhythmic `thrum, thrum, thrum' sound?
