what's the line from the case to the airbox?

[tab1324]

Is this line a breather filter or something? Haven't unbolted the cover from the case yet to check. If so and I remove the stock airbox for pods, do you just install a breather type automotive filter on the hose?

Tom B.

[Czekus21]

Sounds like the crank case breather tube. Running pods, A small pod filter on the crank case should do the trick. I would use a small elbow tube mounted to the fitting on the case. Mount the small filter to the elbow so the filter is pointing up.
Just my opinion. You could also take a long piece of hose mounted to the case, route the hose to wherever, ( under the seat, tank, by the rear wheel, by the license plate etc,, ) and install the small filter.

[EricNW]

what about the other 2 smaller lines running to the stock intake box?

[motoman]

There isn't any..............U workin on an XS11? Post your bike info, year, etc. would be a big help.

[petejw]

the early model carbs have the 2 hose vents,
u can put a small filter on them or leave them
as is, just dont block them off.

[DGXSER]

Yep the 1/2" or so line is the crankcase breather, if removing the stock airbox, I would recommend adding a small air filter to it. On the 78-79 models (or those with that year carbs on them) the smaller 1/4" or so lines are vents to the carb bowls. Those also leave open to atmosphere and I suggest adding air type filters. The filters just keep critters from making homes in those warm holes and plugging things up.

[EricNW]

Ya sorry, it's an '79 XS 1100. I just registered yesterday and haven't gotten the details in there yet.

THe filters on the the hose ends sound reasonable. Is there an issue with not having the positive pressure provided by the intake in the stock setup.

thanks, you guys are really helpful this is an awesome site

[CatatonicBug]

Is there an issue with not having the positive pressure provided by the intake in the stock setup.

What positive pressure? The intake sucks air through the filter. The only reason those hoses are on the airbox is to recycle the fumes from the float bowls bach through the engine instead of "polluting" the atmosphere. It does not have any effect on the flow of fuel to have them connected to the airbox.

[cywelchjr]

What positive pressure? The intake sucks air through the filter. The only reason those hoses are on the airbox is to recycle the fumes from the float bowls bach through the engine instead of "polluting" the atmosphere. It does not have any effect on the flow of fuel to have them connected to the airbox.

That said, when putting my airbox together I made note of how that is put together. From my limited knowledge of fluid dynamics, those are designed to provide a small amount of suction (at least at the higher flow rates) on that tube which would tend to help with scavenging the blow-by gases into the intake flow. I would personally want to find a way to achieve the same affect as scavenging the blow-by gases as I understand it will do nothing more than increase the life of the engine.

[CatatonicBug]

Would it make sense then, to put some kind of hose nipple on the underside of the velicity stacks for the pods, and connect the vent lines there? You could even put a T in the vent line, so it was evenly spread across all 4 carbs. I can't imagine how that would make any difference in engine life, but if you really want to connect them, that seems the easiest way to me.

[cywelchjr]

It might. Remember, the more contaminants you keep out of the oil, which is what a pcv valve does by pulling the stuff suspended in the air of the crankcase out, is going to keep the oil in better shape, which is going to keep the engine in better shape. I believe from what I see looking at the airbox, that the setup in there is designed to function much like a pcv valve does, only without an actual valve since there is not a common vacuum source to connect a pcv valve to like on an automotive engine. I think to do a pcv valve setup, would require 4 pcv valves, and I'm not sure just how much it would affect the mixture and how much re-jetting would be needed to compensate.

[CatatonicBug]

But this doesn't have anything to do with the oil... We are talking about the float bowl vents on the carbs, aren't we?

[cywelchjr]

But this doesn't have anything to do with the oil... We are talking about the float bowl vents on the carbs, aren't we?

The question was about the hose coming up from the engine to the airbox, and he also added about the smaller hoses that are the vent lines for the carbs on the 79 and earlier models. I'm talking about the crankcase vent line which was the OP's first question. The others I agree do nothing except keep the fumes inside an enclosed area.

[dbeardslee]

I think to do a pcv valve setup, would require 4 pcv valves

I put a pcv valve right on the end of the breather tube, with a screen-type filter on the end of that, and wired it up to the frame under the seat. It should provide a slightly negative pressure inside the crankcase. Mikes XS sells them, and they even claim a small horsepower gain. I can smell some fumes when I'm sitting at a light, but I really don't want that hot air going back into my carbs - I want the coldest air I can get going there - but I'm probably just being anal about that.

On the vent lines, I had some small lawn mower filters on the ends of mine. They were great until the paper elements inside got clogged (probably water contamination), and stopped working properly. There's some really interesting physics going on inside those carbs - plug your vent lines and it will cause gas to pour out of your carb bells. I removed the filters after that happened, and have since opted to run them with nothing on the end. If I was going to put anything over them it would be a small piece of screen, or the like, just to keep bugs from crawling up in there. As far as that's concerned, however, I haven't had a problem. My $.02

[slow mo]

crank case vent

K N. makes a filter chrome vent for the xs11 g model 25 bucks up here,,model number 62-1517//1/2 inch,,ride safe ,,slow mo!