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Buell Forum » Old School Buell » Archive through June 23, 2012 » Question about crankcase venting? « Previous Next »

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Imaposer2
Posted on Saturday, June 02, 2012 - 09:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Ok, so I hate to ask such a question but even though I'm mechanically minded in general, and do all my own motorcycle service work, I've never actually investigated it so, here goes...

How much actual volume is moved through the crankcase vent?

Ok, so we all know that crankcases need to be vented to atmospheric pressure in some fashion. Most often from the factory the venting is accomplished through the airbox or such. But, in installing my Forcewinder I'm going to run my crankcase vent hose to a small catch tank. I know that the common hose size used is 3/8" ID, but why is that?

The reason I ask is that the catch tank that I have has hose barbs for 1/4" ID hose. Would those barbs be too restrictive if I left them in place and bushed them to accept my 3/8" hose? I have the pieces I need for this but I can't find 3/8" hose barbs with 1/8" MIP threads to screw into the holes that are tapped in the tank. And I don't have a 1/4" npt tap to redrill and tap the holes to accept 3/8" barb X 1/4" MIP.
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Coxster
Posted on Saturday, June 02, 2012 - 10:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

If you're venting to atmosphere, ANY pressure that 'blows by' will move the gases to the catch can, provided that your catch can is not sealed up. My hoses are 1/4" I.D. and I don't see any problem with the minimal oil moisture ending up in my can. My hoses actually had two low spots before the can and I still see a small coating of oil inside

RightSide
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Imaposer2
Posted on Saturday, June 02, 2012 - 11:32 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

So, you're using 1/4" ID hoses without issue?

I knew the oil and moisture would still pass, but I was just not sure how much air actually flowed through the hose during normal operation. I didn't want the smaller orifice of the 1/4" barbs to prevent adequate breathing of the vent system.
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Ratbuell
Posted on Sunday, June 03, 2012 - 09:37 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

You're not running high pressure, or high volume...all you need is a clear path to atmosphere. It's a vent, not a pressure line.
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Dannybuell
Posted on Sunday, June 03, 2012 - 08:52 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

These engines when run at highway speeds or driven aggressively will puke/vent more than you think. I can easily put several ounces of oil and condensation into my catch can in 1K miles (oil change)..
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Buellistic
Posted on Sunday, June 03, 2012 - 09:11 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Are we trying to say put a PCV VALVE in the TIMING PLUG HOLE ???

If you are, "i" have been running one for years !!!

(Message edited by buellistic on June 03, 2012)
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Coxster
Posted on Sunday, June 03, 2012 - 10:08 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

after looking at this pic, I shortened up the hoses and made things look a little cleaner. Wondering if I shouldn't put the factory airbox back on
carb
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