Elephants trunk

[davidd]

Thanks David, the Ducati one-way breather, is that on your replica race bike or a twin? if on the twin how is it set up?

Chris

Chris,

It is on the racer. I raced the Grey Flash with the timed breather. Also, on my twins I ran the timed breather. Do not be alarmed if the leak does not go away. There is a lot of upward flinging of oil in the timing chest and crank case pressure may only be part of the issue. If the check valve is in the breather itself it seems to me that you just need to run the hose.

David

 

[ET43]

If anyone can read page two they are lucky, as I am still forbidden. ET43
Having just posted this comment and being able to read it, I was then able to scroll up the page to see David's reply ok. Strange eh!

 

[Martyn Goodwin]

For anything to "breathe" in needs to inhale as well as exhale. Have a look at this for what appears to b the solution.

http://www.bunn.co.nz/more.html

I have used the original timed breather banjo for the inlet (with all the internal timed breather parts removed) and a "D" type as the outlet.

 

[Chrish]

G'Day MartynG,

Did you find that the Bunn breather works, how long have you had it in use?

Chris

 

[timetraveller]

I'm not sure that you are correct MartynG. Do you really want to use energy to suck air into an engine and then use more energy to expel it? Is not the problem that leakage past the piston rings can increase the pressure in the crank case which is what can cause engine oil leaks. If the pistons are descending against a partial vacuum then it seems to me that less energy will be required than the same pistons descending against full atmospheric pressure. Having read Mr Bunn's advertising literature I am still not sure how it works so possibly I have something wrong but sucking air in, which might be contaminated with road grit etc, only to blow it out again does not seem like good practice. We need more explanation from yourself as to exactly what is happening before we can decide whether this is a good mod or not. Over to you.

 

[ET43]

I looked at the Bunn system and elected not to use it because I was worried about the temperature of the incoming ( filtered ) air going in to the crank case, especially as I have been known to ride in some awfully low temperatures. I wondered if the cold air mixing with the hot air in the c/case might condense and cause custard. From what I understand, this system could be likened to having two reed valves in the system on two different places, one opening at tdc and the other at bdc so that no pressure is built up in the c/case. Their roles are reversed when the pistons move up and down the bores. You have to think about this! ET43

 

[Howard]

I'm with TT and ET on this - I looked at the Bunn system before I settled on my overcomplicated system. Having kicked out all those corrosive gases left over from combustion, I didn't see the point of repacing them with cold damp air - not even for 0.2 extra horses.

H

 

[vibrac]

As I understand it you dont want to breath in you want to keep the crankcase at negative atmospheric to reduce the pumping action this subject has been driven to exhaustion over many years long before there was a forum. experiments with condoms have proved the effect they blow up to a point and then stay steady
Once again I cannot understand anyone wanting to fiddle about and spend lots of money when a PCV car valve in a piece of hose costing a couple of quid does the job but its your time and your money...

 

[Comet Rider]

To follow from Vibrac's comments
Why do you think that many very high performance normally aspirated engines run vacuum pumps to remove air from the c/cases

QED
Neil

 

[ET43]

As a poor retired chap with a lowly income I do not have money to chuck away. My reed valves are from a Chinese 125cc twin emissions control system which the local bike shop throw away. It fits, with a minimum of modification, on to the end of my elephants' trunk, and does stirling service. My mod is to open up the bore of the exhaust side of the reed block. The machine has not leaked oil since fitting this. As the machine does not exist any more, and if I get the blankety blank starter, another will be fitted to the Comet engine in the trike. I have several in stock! Each to their own I say. ET43