the crankcase breather hose comes off the front of the rear cylinder, and in stock set-up the hose goes into rear of air filter. This allows any oil fumes to be sucked up thru filter thru carb and burned in the combustion process. I would say most remove the hose from back of air box and route it somewhere else with a small filter attached to it, especially with an after market air kit.

The other hose, if that is what you want to call it, looks like a 90 deg elbow, is just vented to air. that is for the upper carb chamber vent. There should be no attachment to the carb that is sealed. There would also be a short hose for the float bowl vent. Since there are no vacuum ports on the carb itself, nothing gets sealed that is connected to carb. There is a vacuum port on the manifold (topside) that a hose is connected to if the AIS is still on bike, if no AIS, then that vacuum port should be sealed. Also a good idea if the manifold vacuum port is sealed, is to check yrly to ensure it did not dry and crack (leak)which it has a tendency to do since it is quite hot in that area.

LuDogStar wrote:
tex, not sure what you mean about crankcase vent hose. However, I did notice twice while cleaning the air box that there was some oil in there and wondered/worried where it came from...

mine has two hoses: one big hose which I believe is crankcase vent and one small hose that goes into top of carb. Can you explain what these do? That might clear up what you mean about extending the hose which I believe you are referring to the bigger of the two
Yes, I was referring to the larger hose which, as Erbman explained, is connected to the top of the rear cylinder valve cover. As he explained most have rerouted that hose somewhere else. The other added benefit of routing the crankcase vent externally is the intake valves will stay cleaner. The crankcase vent is notorious for causing a ball of deposits to build up on the intake valve stems right at the valve itself. Been there, seen that.

great info!

1. what is common routing for crankcase vent hose (externally) and what is used to place on the end of hose?

2. how do I know if i have an AIS and, if I do, should I take it off?

LuDogStar wrote:
great info!

1. what is common routing for crankcase vent hose (externally) and what is used to place on the end of hose?

2. how do I know if i have an AIS and, if I do, should I take it off?
Most I've seen have routed theirs down behind the tank so it comes out near the rear horn with a small K&N filter attached. Mine is routed down the left front down tube. Did that because the tubing I used is too stiff to bend around in the other direction.

The Road Star has an AIS but maybe in your case it has been removed. If it's still there you'll see all of the pieces just below the regulator/rectifier between the down tubes. It'll be connected to 2 tubes on the left side of the engine, one to each head. Not the little oil pipes that form a "Y", the AIS tubes are larger.

Personally I'd leave it on if it's there with the stock pipes. It greatly reduces unburned hydrocarbon emissions.

I found the AIS and I will go with your recommendation to leave it on as I plan to run the stock exhaust for a while.

When externally routing the crankcase vent hose, should I take into consideration that oil may spew out sometimes or will that go away? My thinking is that I need to route it down low so that oil is not spraying all over the bike. I believe that is what you are describing by saying "down the left front down tube" and "near the rear horn" which is on the bottom of the bike

texasscott, thanks I'll look into that.

There won't, or shouldn't, be any oil "spew out" although if you're riding in the cold there'll be some milky looking junk (condensation) forced out sometimes. Keeping it low keeps the mist from accumulating on the bike although Erbman has a handy little filter setup up under the tank that eliminates the problem altogether. He can describe that for you.