Motorcycle Repair: trail 90, crankcase pressure, oil leaks

Question
I have a 1977trail 90, leaking oil on a weep hole on left side alternator cover(not from gasket but rather a hole) is there a common part failure or is it crankcase pressure pushing oil out. please advise me where to look
thanks


Answer
Nick, you may have to email me a photo through my website, if we can't determine the cause here. I am not sure which "hole" you are referring to.

Oil leaks on that side, generally are related to the cover gasket, the neutral switch, wiring harness lead packing coming through the cover, output shaft seal or shift shaft seal. If you are referring to the drain hole at the bottom of the left rear sprocket cover, remove it and check for leaks there. Excessive chain lube will get flung off in that area and drip down when the engine is hot, too.

Certainly, after almost 30 years, the gaskets and o-rings deteriorate and can start weeping. Crankcase pressure will surely aggravate any leaks, so be sure to locate the vent tube and be sure that it is not pinched off for some reason. I think the hose is on top of the right side crankcase half up front. To access it will have to be either to reach down through the battery box cover area (battery and hardware removed) or drop the motor to check it.

Miles on the engine and condition of the pistons/rings can affect your leaks, if they are crankcase pressure related.

Be sure to adjust the valves, check compression and set timing correctly, to ensure that the engine is giving best performance. Tight valves and inaccurate ignition timing will cause the engine to be stressed and overheat, damaging parts inside.

Bill Silver
www.vintagehonda.com