Crankcase Venting 101

HusaBELGfs570 · Nov 14, 2014

So the crankcase vent hose ont the valve cover has to be connected with something to create vacuum on a 570???
I would like to eliminate that hose from spitting oil in my airbox...
I thought maybe guide a hose to the back side along the frame and make a reservoir before the rear schock where the hole is from swingarm it's not a big problem but the oil annoys me and my airfilter is always covered in oil

(dna)

bushmechanic · Nov 15, 2014

the 570 has a scavenge pump so the difference should not be as great as with the old engines

but yes you can add a high speed air valve to the breather, send it up the back of the bike and see if there is any outflow .. if there still is a bit a then a foam filter would be a good idea

badsted · Apr 17, 2017

Venting

Hey guys,

I just got my berg together again, and i cannot figure why its using oil.. Its mostly while i wheelie i have figured. I have blocked my rear vent and the frame, and fitted a one way valve in my breather mod routed to the swingarm overflow bottle. I have attached some pictures, also so you can see my finished berg project!

What do you think about the setup, is the hose too bent, or the valve too early in the line or?..

Engine is fairly new built with rings, valve seals etc..

I fill my oil up to about 1/3 of the oil glass, and after a single ride i refilled more than 200ml.. Then i had a commuting ride just low rpms and bike used almost nothing.. Its not like im revving the **** out of the bike, im really babying it..

I really hope you can help since solving this problem means alot to me..

canolman · Sep 5, 2017

BUMP.
Like the pics above I'm venting out and straight down as I can't go up due to the fuel tank sitting on top of the motor (supermono).
The check valve is always a bit greasy, oil and water mix, as I think on initial start up some oil is blown down the tube before a vacuum forms.
I have an extra vent through the oil filler if I added another through say the clutch cover? Crankcase? Could I seal off the forward rocker cover spigot (the rear spigot is sealed off on all my 'berg engines) using two check valves both pointing upwards?
Is this a really bad idea due to cam and rocker lubrication?

thorgan · Oct 22, 2020

Hey Mr. Bushmechanic, I'm curious about your double-reed-valve engines.

I have a 2005 450 engine that I'm refreshing and I noticed the 2nd hole up in front of the counterbalancer shaft. What do you suppose would happen if that hole were to be simply plugged? There's plenty of thickness there to accept a pipe thread and a plug. I expect that this shouldn't be any different than the earlier engines in function.

I have a '94 vintage 600 engine that Thumper Racing bored out to use a 100mm piston. They also converted it to a wet stator so there's only a single crank seal now and all of the pressure from the 84mm stroke is pushing past the single factory reed valve. I have not noticed any detrimental effects on the left side crank seal from the vacuum either.

I'm also thinking about manufacturing a tube that directs oil, via the rear vent above the ascending cam chain, over to the rockers (maybe I'll split the flow and try to get oil directly onto the cam follower bearings via a pair of small holes in the rocker cover).

Any thoughts on these modifications?

bushmechanic · Oct 25, 2020

Hi there Thorgan, I think all those ideas are fantastic, I didn't simply block off the second hole because I figured it was necessary for something. Perhaps not. In any case redirecting the mist up to the cam followers is a great idea.

Would love to see some pictures of the oil lines to do that
Cheers !

Crankcase Venting 101

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