I am running a Polini 75cc kit on my Minarelli. The carb I am using is a SHA14-12 that I bored out to 9/16" (14.29mm) and a manifold that I also bored out to 9/16"
Here is the problem: The bike seems to run lean in the mid-range. What happens is when I am going along at say a constant 35mph the engine will heat up and then tighten up, not really sieze, but getting there. If I blast up a hill at WOT I do not get this condition. The plug is a rich chocolate brown.
I am running Redline oil at 40:1
I think that I have about 150-200 miles on the engine.
So the questions are these:
Do I have to break it in some more? The Polini instructions say 300 mi.
Is there anything about the Dellorto carb that makes it run lean in the mid-range? Is there anything I can do to it other than changing jets?
Thanks in advance for any info given