Terry Syd
Addicted to ArboristSite
I don't know how the base compressions were measured, but those figures seem high to me - especially since this engine isn't using a crank with stuffers (and the transfers extend all the way into the cases). Perhaps it is the formula that is used, but I wouldn't figure the stock 64cc engine having a base compression as high as 1.62.
The 1mm increase in the venturi of the carb may help, but I'd expect that a new carb would be a better approach. Say the intake manifold had a 20mm diameter, I'd be looking for a carb with something like a 19mm venturi and then blend the throttle chamber of the carb into the intake manifold. The smaller the throttle valve the better.
Perhaps someone has used a bigger carb on the Dolmar and can chime in with what is available.
The 1mm increase in the venturi of the carb may help, but I'd expect that a new carb would be a better approach. Say the intake manifold had a 20mm diameter, I'd be looking for a carb with something like a 19mm venturi and then blend the throttle chamber of the carb into the intake manifold. The smaller the throttle valve the better.
Perhaps someone has used a bigger carb on the Dolmar and can chime in with what is available.