Valvola Carb coming loose problem

 

 

Quite a few people are having problems keeping the carburettor of the Valvola engine in place, increased
tightening of the drawbar does not stop the carb coming loose it only ends up crushing the carb spigot.

One method of preventing the carb from coming loose is, whilst it is still fitted into the housing, drill two holes through either side of the housing and carb and tap to 3mm. Two shortened 3mm cap screws can then be used to prevent any future movement of the carb.
   

 

 

 

Update

 It would now seem that the problem of the carburetor coming loose is due to the profile of the cutout in the drawbar  being incorrect, i.e. too large. Only the end of the cutout grips the carb spigot, this is not enough to prevent the carb becoming loose. A simple modification will overcome this. File the other side of the drawbar to create a much shallower cutout that will fit tightly against the full width of the carb spigot.
Note :- The drawbars of current Valvola engines have the correct profile.