I just rebuilt my engine and carb, had the shop tune the carb for me and the bike is running great. I made a run from gainesville to st augustine with the great weather and found something weird going on. It seems like whenever I go over about 70 miles/hour, (hit 100 top on some of the backroads) the carb doesnt seem to be keeping it all in, its like some of the gas vapor is getting sucked out of the air cleaner? After one of the higher speed limits I got into a town and when i looked down there seemed to be a slight oil/gas residue film on the rear rocker, all of the oil tank, on the top of the battery box and on the side of the secondary belt cover. I wiped my finger across the inside of the bottom of the air breather and the oil/gas mixture was sitting there. Why is this mixture getting pulled out at high speeds? Is the high speeds causing a strong vacuum that is pulling it out? Is it running too rich? the bike is running very smoothly. My bike is a 1992 sportster 1200 with a CV carb.

 

if you fill the oil tank all the way up to the full mark on the dipstick, they will puke oil out of the aircleaner.

 

Yuo are pushing a lot of oil vapors thru the top end of your engine and it all can't be drawn in to the carb. When I had a Sportster I always kept the oil level about a half inch from full. You might want to post this question on the Sporster forum for a more definitive answer.

 

That could be. Also, one or both of your breathers may be leaking. Pull your air cleaner and you'll probably see where the leak is coming from.

 

Have you got the accelerator pump turned right towards the center of the carb bore?