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Opinions on 501 crankcase venting mod

A

ajw30

Joined Oct 2010
20 Posts | 0+
I have just recently had some work done on my 01 501 and one of the mods was to vent the crankcase through the exhust. Craig at HRT racing hs been doing this mod to all sorts of racing bikes for years so I had him do it to mine. All he did was weld a small tube on the header under the gastank petcock. Now instead of venting through the carb it runs through an air injection check valve right to the exhaust. I have ridden it once since the mod but ran into a small oil leak so its back at the shop. He also dialed the bike in so I could start it cold with my left leg and one kick :cheers: should have it back wed so I can ride it to work :D
 
Interesting. Sounds like a lot of work. What is the benefit of venting to the exhaust?
 
from what craig explained to me is when the exhaust is exiting the header the force created from the exiting gasses pulls the pressure out of the crankcase creating a lower pressure inside the motor. He showed me the mod he has done on some other bikes such as a TT 500 dirt tracker, An old KTM with a rotax motor, and a KTM 640. I thought it was an interesting Idea so I wanted to give it a whirl. I will try to post some pic's when I get the bike back. It is actually a very easy mod if you know how to weld. And oh i did read the linaweaver crankcase 101 forum and that is where I pulled the part number for the air injection check valve.
 
Theoretically the negative crankcase pressure will increase H.P. , at least that is what Dale had said. What I like best about the idea of venting through the exhaust is that you won't get oil dripping out of the vent tube. If the bike flips over though you still may get oil in the top end running in from the exhaust header. A very cool race mod nonetheless.
 
I do know that it works because it actually sucked in the clutchcover gasket below the waterpump cover. The gasket was just put on and no gasket adhesive was used but needless to say that I lost every drop of oil out of the bike. But it now has a fresh gasket on with adhesive on it so it wont happen again.
 
cool can we see a picture?

it should be pulling a higher vacuum than just a high speed air valve

on multi cylinder engines the exhaust venturi effect is a much better idea becasue the pistons going up and down out of phase cancel out the negative pulse you get in the single when just one piston travels upwards.
 

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