Mikuni VM36 Roundslide: Venting Question

[TeeCat]

Hi, Mikuni VM Roundslide experts.

Quick question:

I have looked at the literature for this, but can't seem to find an answer to my specific query. On my single Mik VM36 roundslide, there are three vent hoses. One is at/off of the bottom of the bowl, and the other two "straddle" the bore, at the body. On my single carb conversion, the carb is in such a place that, when the top two hoses "dribble" (just a tiny bit), they do so on my left side cover, which is painted. So I just wanted to lengthen the tubes and run them just out of the way.

That's easy enough, but I noticed that the tiny bit of dribble seems to be more like clean oil than gas... or maybe it's gas that has the volatiles evaporated off, and feels more like oil. (Incidentally, my bike doesn't seem to smoke or anything, so I don't think I have any "oil control" issues up top.

Anyway, what exactly do those tubes vent? Do they balance the carb's atmosphere somehow? And do I need both? Can I cap one with a vacuum cap and leave the other one open, but venting away from my side cover? If I have to leave them alone, I suppose I could. I just hate those little dribbles.

Thank you!

TC

 

[racerdave]

They should not dribble. Check your float height. Is the bottom tube on the center bowl nut? That would be a drain hose.

 

[TeeCat]

dave, yes, the drain hose is off of the lower part of the bowl. The upper two are off of the bore or upper part of the body, and over time, they seem to collect a little bit of oily feeling "condensate" or something. There are no observable issues with the way the bike has been starting or running, though I confess that I may keep my warm idle a little higher than it needs to be. The float level is spec, and this is a new carb since Oct '10, when I did the conversion, just fyi. I just wanted to address this because I'm neurotic.

From powersports.net:

"MIKUNI CARBURETOR VENT LINES - Mikuni OEM quality vent lines keep fuel off your engine."

I was basically wanting to make mine a touch longer to get them away from the side cover. Thanks!

TC

 

[racerdave]

Don't make them to long where they could be sucked on by "airspeed" passing by them. That can lean down the top end.

 

[TeeCat]

Dave, thank you... I just made them about two inches longer so I could zip the ends together and just tuck them slightly behind the rear-top of the cover (clear of the chain, though!) and away from the painted surface. Should be fine now. Still gotta toss a little zip tie on there.

Thank you!

TC