QuestionHello, I have a '00 Nighthawk 750 with 11,500 miles on it. I've been riding it for the past five years mostly rural and city driving. The valve cover breather tube has normally contained very little discharge. It was thick and contained mostly oil. I had to empty it every oil change.
Recently, I began commuting on the freeway 30 miles roundtrip. I noticed the other day the breather tube was full. The discharge was very thin and smelled like gas. I emptied it and checked again yesterday and it has 1/2 inch of the same discharge. I checked the air filter, checked the operation of the choke lever and checked the routing of the tubing. All OK. Any idea's? Or is this normal with the change in my driving habits? Thanks.
AnswerHi Jerry,
The problem may be related to the change in habit, but not the cause of the problem.
1) Check oil level with MC level on level ground.
Overfilling may be due to excessive amount of oil, or by varnished carburetors leaking fuel into the crankcase and raising oil level. (I believe you properly fill the oil as often as you service the MC.)
Combustion blow-by gasses positively pressurize the crankcase. A low pressure exists at the crankcase vent and vent hose. The high pressure rushes to low pressure(i.e.; flat tire, fart) some of the oil may be forced out with the pressure. Especially if the oil is overfilled.
Regursion from the carbs may have placed some fuel in the airbox drain tube and into the vent tubing.
It's tough to say without being present and making a few checks.
Send me an email address as requested and I'll return several tech files that may be helpful.
Respectfully,
Mark Shively
