Quote:
Originally Posted by Clan
you need to determine if the mixture is weak or rich when the problem happens . with the air filter off spray some brake cleaner down the carb , if the revs go up its weak ... then introduce some air into the brake servo line some how when its playing up , if the revs go up its too rich ..
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Brake cleaner no longer works!
All the VOCs have been removed so it's about as flammable as a wet lettuce! Need to ue WD40 as that is STILL a petroleum distillate.
Also, if it's black smoke, it's running rich. I don't know which carb it has, if it's that horrible Solex twin-choke thing then it might have one of those vacuum operated accelerator pumps on it. In common with Webers so equipped, two things can cause this to happen. One is the diaphragm in the carb that the vacuum operates has gone weak and/or has a pinhole or split in it that opens up once warm second likelihood is the small bore vacuum hose, usually only a couple of inches long if that, can have a pibhole or is perished but again, once it gets hot and flexible, allows air in which pushes against the diaphragm causing a discharge from the booster jet.
Not sure when or if they changed from this design or if it ever had it but i've seen many similar engines that have had this problem. Also general wear in the carb can sometimes cause it but isn't quite as common.