I've been doing some work on my wife's 1988 4-speed Evo 1200 and for the first time today I removed the air filter. I immediately noticed that the bolts that hold the back plate of the filter to cylinder heads do not have vent holes in them. This seemed odd to me until I realized that the motor vents from the black hose that sticks out by the oil filter on the cam cover.

My question, can I change the solid bolts to breather bolts and then close off that stupid looking hose without creating any pressure issues on the bottom end of the motor? I dont want to vent into the air filter. I' set up a hose system that vents into a smaller filter so that crap doesn't go into the motor. The hose at the can cover likes to get oil all over the underside of the bike. I know it's the underside but I work to keep my bikes clean.

 

I don't think so, my '91 was first year with head breathers. I think the lifters, pushrods, tubes changed and maybe the cam chest venting.

Of course, a 70 year old design should allow some modifications. I bet Hammer or NRHS will know.

John

 

Don’t think that you can … however, I could be wrong. I’ve a 1987 Sportster in my garage set-up the same way.

I actually prefer venting to the AC filter. Every bike I’ve purchased vented to the atmosphere leaves an oily friggin mess on the engine and frame.

 

You can direct the oil into a catch can if you hate cleaning up the oil..

 

I routed the breathers to a separate filter on my Deluxe and just clean the filter every few thousand miles. I figured I'd do the same thing with the Sportster if I couldn't close off the breather at the cam case.

 

They don't have the required passages through the rocker boxes for head breathing. You're better off just running a small filter; it's a lot less hassle.

 

That's what I was looking for. I had the rocker boxes off to replace leaking gaskets but I never removed the heads nor did I ever think to investigate. I only took the air cleaner off because I have a sticky throttle, which turned out to be crap Avon grips. I figured that the head was not configured to allow for pressure to escape. Thanks!