Max and fellow learkers 
this weekend I had a customer in from PA and he mentioned that he was having a problem with the gas tank accumulation a fair amount of vacuum. He would notice this when the gas cap was removed. He did not say that it was causing him to brake down or that it lowered the miles per gallon but he pointed out that there is a vacuum operated valve on the clear hose from the charcoal canister to the air filter on this 85 and that when he replaced the valve the vacuum in the tank problem stopped. I thought to myself he must have one of the only gas tanks in the country that will hold vacuum and that this is a acuum leak that would be not so easly detected 
B. Bob