I've got a '91 Sportster 1200 and when I remove the oil dip stick there's a good gasp of air from the oil tank. It's building up negative pressure in the tank (vacuum). I traced all the lines on the tank, and they all correspond to this picture. But after the vent hose runs behind the gear case cover, WHERE DOES IT GO? I pulled up on it just a little to see if it was hanging free, but it won't come out. Either it's hooked up to something, or it's being held in place by something I can't see with the gear case cover on.

 

Mine just ends there but it's an 07 so I'm not sure if yours is the same.

 

Appears to go into the side of the engine and attach to a 90 degree fitting. Not a clue to what the fitting is plumbed to. Guess the engine vent system takes care of oil tank vent. Sure the oil pump can overcome the slight vacuum of the tank. Better then pressure. If mine happens to kick back hard, it will blow the loose fitting dip stick out.

 

Thanks for the reply's. I'm gonna ride down to the dealer and see if they can lend any insight to. It's bike week here so you can imagine that place is PACKED.

 

The vent line connects to the cam gear area, vents inside with the cams.

I've got a 1991 as well.

John

 

Thanks again for the reply's!

So the oil tank is vented into the crank case, and the crank case is vented through ??? Where? I've looked at several drawings for EVO's and each drawing seems to have a completely different answer for where the factory vent is at or where it goes.

So far in trying to resolve this I've found and fixed four other problems with the bike anyway LOL! Screw holding a relay in had fell out, zip tie holding the oil lines away from the exhaust was broke, and the fuel tank vent hose was pinched shut by the positive battery cable that had corroded terminals... Silly stuff you can expect buying a 22yr old bike. No complaints here!

 

Your crankcase vents through the cylinder heads into the air cleaner, unless a previous owner install an outside breather kit. I've owned my 1991 since brand new, so if you have any questions, feel free to PM me.

There is also a transmission vent hose that comes up out of the top of the transmission area near the starter. It just vents to atmosphere as far as I know.

John

 

Roger that. I checked all over the cylinder heads, and can't find any place a hose would hook up at all. While looking for the crank case vent, I DID find a hose coming off the top of the S&S carb. that according to their manual is supposed to be going to the VOES system... It's running to open air!

EDIT: Found out what VOES is, does, and where its SUPPOSED to be on the bike.. I'll be shopping online for one to install here shortly.

Is there a chance you have a picture of where the crank case vent is on your '91? I've crawled ALL OVER and can't find anything on the heads at all. THANKS!

 

If you have the stock air cleaner set up the vents are in there. 2 big bolts that actually hold the back of the air cleaner on the bike. Those bolts are drilled through and act as vents for the oil system. Should be 5/16 allen head screws or something crazy like that.

 

Your breathers are on the carb side of each head, above the carb. There are breather bolts that are hollow, and there are aftermarket breather systems. They all use the same threaded holes in the top carb side of both heads. Please do a search of this forum, there are hundreds of references. They aren't leprechauns or unicorns.

I can't provide pictures of mine because it's hidden from view, unless I had a fiber optic camera. I have not had to change out any lines so far after almost 23 years, but garaged in SoCal probably helps.

Check DK Custom, Hammer Performance, or NRHS for information on breather systems.

John