I came across this short description of why Evo's leak oil.. It's about the Spyke KVS valve. I've had one on my evo since I've owned it and never to this date has it had oil leakage or seepage except for loose rocker covers (I use rubber seals only) It's easy to fully understand it's purpose and functionality and I would believe it to be a must for anyone that relocates their breather system to atmosphere (instead of the factory design to base of the carburetor). Actually I would think that if you install a bigger cam with more valve over lap and still use the factory setup of the breather system I would think that the possibility of reverberating air could possibly charge the crank case due to weak umbrella valves. How many times have you heard of someone having problems with oil bubbles at the cylinder base gaskets? Do yourself a flavor and check it out......

http://www.jpcycles.com/instructions/pdf/432-271.pdf

 

I'll just leave this here:

http://www.nightrider.com/biketech/crankvent_test.htm

 

I was only referencing the reduction of positive pressure in the crankcase and oil leakage throughout the motor. Not soliciting a performance upgrade.....

 

I was only referencing another published point of view.
I don't have a dog in this hunt.

 

http://www.jpcycles.com/instructions/pdf/432-271.pdf

That is a snake oil advertisement if I ever saw one.

"Deeper more powerful sounding engine"....Absurd.

My big twin has never had an oil leak problem, unless there was a bad seal or gasket. Simple.


How would a camshaft difference affect the breather system? The valves have nothing to do with the volume of air in the crankcases, or the timing of the breather system.

As far as base gasket leaks go, the best thing to do is solve the problem at its source, the uneven sealing surface at the base of the cylinder.

Have the base of the cylinder trued by a machinist while the cylinder is removed for the base gasket replacement.

 

Installed new base gaskets, roughly 10,000 miles ago, along with other stuff. No more leaks. Works for me.

Ride Safe,
Harold

 

It's just a suggestion to help alleviate the poor EPA design.

But here goes my explanation, right or wrong it sounds logical. Doesn't it?

The more overlap in the intake and exhaust valves would create a greater amount of reverberation of airflow in the intake. As the piston is on the exhaust stroke and the intake valve is starting to open the piston will create a positive pressure in the intake (overcoming the atmospheric charge in the plenum). If you still have the factory setup of the breather system to the base plate of the carburetor this positive pressure can be displaced back through bad umbrella valves and into the motor creating a positive pressure that will in turn make your leaks worse...Yea, Nay, Logical or not?

 

I think you are reaching for something theoretical that is not there...

Leaks are caused by bad seals and gaskets. Yes, they can be caused by a breather problem, such as a mis timed breather gear, or a damaged breather gear. The krank vent is nothing but a fancy check valve.

When I had a base gasket leak on my Evo (at 50,000 miles) I had the bases of the cylinders trued. No more base gasket leak. The bike ran leak free for the next 80,000 miles (it has now gone another 10k without leaks since overhaul).

 

Dan89, maybe i am reaching a little and i do follow you 100%, truthfully engineering has always been one of my areas where good enough is to me, not good enough and therefore I'm always trying to improve thats all... thanks for the replies...

 

I put a Spyke crankcase vent "check Valve" on my 86,could not stand the sound it made at idle, just like a rod knock,took off,(waste of $100 bucks),drilled hole in back off k&n breather, put fitting close to carb any mist will be sucked into carb,works great and no oil in air filter or anywhere else. Been that way for two years now what a easy fix!!!