I dont know if this will help with your issue but...On my 212. I disconnected the rubber hose from the valve cover to the carb housing and meshed over both orifices. Then I drilled about 40 holes around the air filter housing to let air in. Im sure its not as much flow as you have now, but a lot more than before. Then I cut off the flange on the exhaust and made a 1" header 16" long. I dremeled around the inside of the flange to open it up.(home port job)
I did not change jets. I was going to drill out the jet and then I thought . Lets just see how it runs first. It runs fantastic. Very torquey and pulls hard up top also. And thats with a 60t rear sprocket and a 230lb driver. I pulled the plug and its a nice carmel color with just the slightest tint of white creeping in. So to be safe I mix12 ounces of 93 octane in each tank to raise octane and prevent detonation.
Nice tan plug with no white. I think ive got this thing tuned about as good as its going to get......My point is........I prob have close but a little less air available than you do.....with a stock jet. And a/f ratio according to the read the plug meter is:thumbsup: The engine wont use more air just because its there Nor will it use more fuel because its there. You are prob way to rich. All my runs were checked on 4000-5000 rpm runs wot and then pulled over and checked the plug. No tach but no g#&*@*^r either.
Short of bumping the compression or adding cc's. Or porting the head and flowing the carb. The little engine doesnt want any more. Remember.....lean is mean! Just dont want to go boom boom. LOL Thats why I mix in a little 93
