What do people do with Breather Outputs With No Airbox?

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Like many I've disposed of that dust coffin that was the old airbox.

In the 'ol days we used to strap a tin can to the frame to catch oil.

Anyone got any suggestions..

What do you guys do with your breather outputs? When you dont have an airbox?

Retiredgentleman

Still have my airbox, but I use 2 clear plastic tubes running down from breather output to 2 foam filters just in front of rear wheel. Works good.

grizld1

Matter of fact, Jake, I run mine into a tin can! WD40 can to be exact, middle drilled out for the line, edge of the top perforated for breathing, piece of air filter foam pull-tied on to keep debris out of the line on the back-pulse. Since I've ditched the safety relay and moved the starter solenoid under the seat there's plenty of room for it under the right sidecover.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

There are small breather filters made for this. Cheap K&N repros are available at most auto parts stores, even at Walmart. Of course, there are real K&N breather filters as well. For this application, you really don't need the best filter, if your hose is long enough you probably don't need a filter at all. Most bikes from the late '60s and early '70s just had a pipe or hose vented right to atmosphere (no filter).

Some mount the filters right on the breather, above the carbs and engine. I don't think this is the best method. That filter will sweat oil and if you happen to over fill the engine with oil, it will dribble out the filter. Having it above the carbs is gonna make a mess. Most of us run hoses back and down, by the battery box or behind the motor. Some position the end of an unfiltered hose over the chain so any oil or mist will aid in lubing it. I had a K&N breather filter that came with a box of parts so I used it. I ran 2 hoses back to a brass "T" then one down to the filter. The minor oil sweat I get doesn't harm anything back down behind the motor there.

xsjohn

Biggest problem when I tried to get the breather out of my stock air box was that it STINKS....pull up to a stop sign and think....dang these cars smell....smelling own ass.......sounds a bit weird too.....

John

Tomterrific

The generic Motormite Power Brake Check Valve will plug into the stock breather hoses. The stock hose is the perfect length to run to the top of a pod air filter. My '77D has two breather hoses with a check valve in each. The outlet of the check valve rests on the top of the K&N filter. Any oil mist is absorbed by the filter element. The check valves are one way so dirt will not be breathed in through the valve.

The check valves are one way -out- so a vacuum is in the crankcase through the pumping motion of the 360° pistons. The check valves are $5 each at Advanced Auto. I run the same check valve on my old Triumph and it cuts down oil leaks.

Tom Graham

TeeCat

I read this thread with great interest. Presently, the breather tubes on my '73 are open to atmosphere (and seem to be clear), and appear to have been that way from stock. However, I'm considering doing 5twins' idea because they mist and are a little messy.

But Tom's idea about the check valve also has me wondering if running those and creating a little vacuum in the crankcase might help to minimize my drooling left crank seal. Thoughts appreciated.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

I've since changed mine to the set-up Tom recommends and I like it better. It's simpler, less cluttered, and should help control oil leaks (even though I don't have any at the moment).

Retiredgentleman

That check valve looks like something I need to try. I'll buy 2 and give it a try.............great tip.

TeeCat

Well, then I'm going to try it, twins. Reason suggests that if I can create a little bit of vacuum in the crankcase, leaks might be somewhat mitigated. Thanks to you both. I'll be stopping by Advance Auto today.

ine hang all the way down, though, so I might have to rig mini filters at the ends of the vacuum valves.

I don't know if you saw my other post, but I'm noodling a trick little "bib" for her... a little racing overflow canister-type catch can to pick up stray oil droplets that would otherwise end up on my exhaust. I'm not beyond eventually trying a speedy sleeve either.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Here's the one I used (well 2 actually) Power Brake Check valve part # 80190. You can't use a PCV valve because they have a ball bearing in them and it won't move fast enough at higher RPMs. Basically, the thing won't function.

TeeCat

Oh, they have a Help isle, so I'll look there first! Thanks, sir! Smile

Now I'm really curious; I wonder if the vacuum created in the crankcase is literally significant enough to discourage oil from finding its way to potential "unauthorized" exit points? Guess I'll find out!

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

I've got a '74 TX 650A that's kinda flat-tracked, with twin K & N breather filters mounted just above the twin K & N air filters. My problem is that the oil-fill specification seems to be screwy for the '74's, and she pukes oil out the breathers fairly bad. Anybody see this before?

I think I'll try the vacuum booster valve trick too, tho, just fer kicks.

jayel

on my 74 I ran long tubes down the back frame tube to dump under the engine with the check valves tucked between the starter and swingarm area and yes the 74's say 2500cc but are happier with 2300cc they were around the time of the case capacity changeover and Yamaha dealers were remarking the oil dipsticks per a service bulletin

penn71911

metalredneck... That bike is sweet... got any close-ups?

TeeCat

metal... I'm getting ready to install check valves on my stock breather tubes that run to just below the the centerstand hinge, but I'm going to install miniature K&N knock-offs on the exit ends of the valves to catch mist. I'll see how it works and post pics.

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

I'l be posting some more recent shots with the new bars & tires tonight, Lord willing & the creek don't rise. I took her out last night for a rip, and there are still a few minor bugs, but she works OK for a field wreck plus about $450 in parts.

TeeCat

I have not yet had a chance to install my check valve/mini-cone breather setup, but I was curious as to how this works in theory and practice. I know that the idea is to maintain a fairly constant vacuum in the crankcase to help mitigate blowby and oil leaks, but I was curious as to how our chosen valves are different from PCV valves... just speed of operation? Also, what happens to any possible excess vacuum that might be built up in the case?

Just curious... any knowledge imparted is welcome.

TC

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Yes, I think speed of operation is the difference. A PCV valve with a ball bearing can't move fast enough as the engine pulses increase with RPMs. I don't think excess vacuum is a concern. The flapper valves probably don't seal 100% and then there's all those oil seals that could suck some air in if need be.

TeeCat

twins... thanks! Good info!

Hey... did you have a LOT of trouble getting the larger end of your valves to fit into your hoses? My hoses are clearly stock, but are too small to insert the end of the valves without the risk of splitting. So, I got a few inches of the next size up to overlap the ends (with glue) of the stock tubes, and then clamp the valves into the other end; they fit perfectly and without forcing them. Then my neat little filters will go on the other end of the valve. I'd planned to use KrazyGlue for rubber to adjoin the hose... I think it's basically vulcanizing glue.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

I got some new hose from Mike's and they fit right in. It's nice and soft.

.ET. · Full Member Joined: Jul 22, 2008 Posts: 28

Metalredneck - your problem is to much oil. Yamaha had a lot of complaints about this

www.650rider.com/index...pic&t=3458

that's were i got my info on it....

tweedy64

What size hose for the oil breather , is it 12mm ? Got an 80. cheers guys

xsjohn

I have an idea where I would stick that tube..............xsjohn

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