Roadstar Crankcase Breather Modification

I didn't want crankcase oil misting into my carburetor and possibly making my valves stick.


NOTE: This modification has not been tested thoroughly and is a work in progress.
It works but I have yet to test it out under extreme summer temperatures of Florida and it may require using tubing of a different type material. Don't do this modification unless you're the experimental type like me and willing to have a mess of melted neoprene on your cylinder fins or pushrod tubes, not to mention the oil.


The stock crankcase breather tubing which connects to the stock air cleaner housing has a 3/8" dia. hole but where it connects to the air cleaner housing it's reduced to a 1/4" i.d. by the nipple connector on the rear of the housing.

Therefore, although I would like a larger diameter vent, apparently 1/4" I.D. is sufficient to function or at least the engineers a Yamaha feel it is. I took an 18" length of 1/4" I.D. neoprene tubing with a 1/16" wall thickness (which gave it a 3/8" O.D.) and slid it inside the stock tubing about 3/4" and secured it with the stock spring clamp.

I routed it behind the rear cylinder push rod tube, down alongside the crankcase, exited it just below the frame and cut off the excess.

(Note: tubing diameter is always measured by I.D. and pipe diameter is always measured by O.D.)