General Motorcycle Question from a True Suzuki Enthusiast

[Anonymous]

Since my GS850 is torn apart for the winter I thought I would work on my 1973 Honda CB350 Four. When I purchased it the bike was not running due to the fact that the owner had rebuilt the motor and just lost interest. Well I have since brought it back to life but have been noticing some strange things happening. For the last week it has been running pretty well, but last night I noticed what I think is smoke coming from the breather hose that comes off the top of the head. On my GS850 this hose connects to the air box. On this bike it just runs towards the back of the bike and hangs there. There is no place on the air box to connect it.

What exactly does this hose do? Should it be blowing or sucking?

What would cause smoke, or exhaust to come out of this hose? Incorrect valve adjustments (which I did adjust)? Did the previous owner screw something up while reassembling the engine?

Sorry for the non Suzuki question, but there seems to be a lot of general motorcycle knowledge here.

Curt

[Pete's GS]

Well, it should vent to the airbox but if there's smoke it sounds like you have some blow-by past the rings. Is the bike's engine broken in ?Sometimes builders will put too much oil on the piston skirts--only one drop in necessary on each--and over-oil the cylinder walls where none is needed at all. Then they don't rev the bike enough upon start-up. One-half of redline for 30 seconds then shut it off to check for any leaks. Then go out and ride it. At least use 2/3s of the way to redline within the first 400 miles, then gradually to redline and a quick back-off from the throttle to increae vacuum pressure on the rings to fully seat betweeen 400 and 1000. I know your bike wa '73 or '74 if it's the Four but I'm pretty sure even then manufacturers were venting to the airbox. Alternatively, you could put a breather on it from Emgo or K & N.

[Anonymous]

It should be blowing. All of the diesels I drive have a 1" tube coming off of their engines (crankcase vents) and they smoke (drip oil) so don't be too worried about a filter as long as you keep the oil away from your tires.

Steve

[Anonymous]

A 1973 would have just vented to the atmosphere and, yes, there would always be some smoke coming from it.