Crank case breather

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Crankcase pressure valves are not limited to motorcycles, see this for the Citroen 2CV, also a twin in which pistons reach TDC together and which leaks when the pressure builds up. They also claim a power increase..

http://www.ecas2cvparts.co.uk/valve-cra ... -1401.html

Interestingly, the oil filter for the 2CV also fits the Commando. Useful when living in France!

Phil.
 
Re breather

Hi all.What i have done to releive pressure is to simply drill the inlet rocker cover,fit a brass plumbing fitting and connect pipe to it and then existing breather pipe,works a treat no more leaking tacho drive or any other weeps and i'm sure it go's faster!!!..............Cheers Andy
 
Yeah, but you've got to remember that you are still sucking a crankcase full of air in at every upstroke. What it means is that your engine is a big air pump both ways, ie. top and bottom of your pistons. Takes power to do that.
I suspect that early Jap twins weren't oil tight because of superior quality but because they used 180 degree cranks. Therefore, the crankcase volume didn't change because as one piston was going up, the other was going down.
 
PJL said:
Crankcase pressure valves are not limited to motorcycles, see this for the Citroen 2CV, also a twin in which pistons reach TDC together and which leaks when the pressure builds up. They also claim a power increase..

http://www.ecas2cvparts.co.uk/valve-cra ... -1401.html

Interestingly, the oil filter for the 2CV also fits the Commando. Useful when living in France!

Phil.
Click to expand...

Hi Phil,

Do you know if the valve you have linked to above is a reed valve or plunger valve?

Does anybody know what pressure is 'pushed' out of the Commando engine? Do these valves have a pressure rating? My concern is that if you got the wrong type of valve it could actually cause pressure to build up blowing seals :cry: or is this not a concern?

There seems to be lots of these type of valves available in the USA but I'm finding it difficult to track any down in the UK/Europe. Most of the plastic valves in the USA are around $5 but most suppliers won't ship to Europe (We're way to dodgy over this side of the pond :D )

Kevin
 
Hey Kevin,
I just went down to an auto parts store and described what I wanted and they handed over a one way fuel valve with 10mm spigots at both ends. Fitted straight into the breather line from the timing case up at the oil tank. Cost was about AU$30.00. About 14 quid. Works a treat.
 
I've used the Bunn breather for about 5 years with no problems, it's small, light and simple, it works on the the same principle as the Krank Vent, but it lasts!! I bought a Krank Vent, (5 times the price, and it lasted 10 miles before the disc dissappeared...so much for nuclear proof!)

rexbunn@bigpond.com or (02) 9899 9439

http://www.panther-publishing.com/defau ... ntentID=35


I used the original one way valve. it arrived within a couple of days, took 5 minutes to fit and has given no problems
 
I've been using the Motormite/HELP 80190 check valve for 4-5 years. It is a nice solution in that it can just replace the 062617 adapter fitting where the piping from the breather changes diameter. The hose wants to make a right angle bend there anyway. The hose sizes are perfect for it. (This is on a '72.) It took me a while to realize it but I no longer have oil weeping out of the case halves below the carbs or the tach drive. Both of these leaks had been there from brand new.

"Cheap plastic" works for me.
 
Fullauto said:
Hey Kevin,
I just went down to an auto parts store and described what I wanted and they handed over a one way fuel valve with 10mm spigots at both ends. Fitted straight into the breather line from the timing case up at the oil tank. Cost was about AU$30.00. About 14 quid. Works a treat.
Click to expand...

Is this the kind of valve you mean? if so what would be best bore size?

http://cgi.ebay.co.uk/Fuel-one-way-valv ... 0308144478
Robert
 
rbt11548 said:
Fullauto said:
Hey Kevin,
I just went down to an auto parts store and described what I wanted and they handed over a one way fuel valve with 10mm spigots at both ends. Fitted straight into the breather line from the timing case up at the oil tank. Cost was about AU$30.00. About 14 quid. Works a treat.
Click to expand...

Is this the kind of valve you mean? if so what would be best bore size?

http://cgi.ebay.co.uk/Fuel-one-way-valv ... 0308144478
Robert
Click to expand...

Hi Robert,

Thanks for the link. Not sure of the exact bore size of the existing breather pipe. The valve on Ebay seems to have a very small bore size, I suppose it is a fuel valve.

I really appreciate you posting the link.


Many Thanks

Kevin
 
Is this the kind of valve you mean? if so what would be best bore size?

http://cgi.ebay.co.uk/Fuel-one-way-valv ... 0308144478
Robert[/quote]

Hi Robert,

Thanks for the link. Not sure of the exact bore size of the existing breather pipe. The valve on Ebay seems to have a very small bore size, I suppose it is a fuel valve.

I really appreciate you posting the link.


Many Thanks

Kevin[/quote]

Hi Kevin, I noticed the bore size was 3/8th and Fullauto said his was a fuel valve with 10mm spigots which is about the same. That's why I was wondering if this would be ok.
Cheers
robert
 
I've been fitting these valves for close on 40 years and generally any check valve will do providing it is big enough, will stand heat, engine fumes, oil, is fast acting and has a very very low blow off pressure.

Hope this helps,
Cash
 
cash said:
I've been fitting these valves for close on 40 years and generally any check valve will do providing it is big enough, will stand heat, engine fumes, oil, is fast acting and has a very very low blow off pressure.

Hope this helps,
Cash
Click to expand...

Do you reckon the one I posted on would do the job then?
 
cash said:
I've been fitting these valves for close on 40 years and generally any check valve will do providing it is big enough, will stand heat, engine fumes, oil, is fast acting and has a very very low blow off pressure.

Hope this helps,
Cash
Click to expand...

Hi Cash,

Thanks for the reply. Can you recommend a brand/make of blow off valve you have used? You mentioned my main concern above, the blow off pressure, get it wrong & it could get nasty :oops:

Kevin
 
If those are ball-and-seat type check valves, they won't respond fast enough to be effective. That is why the brake booster flapper valve and (better yet) the reed valve units are preferred.

Ron L
 
I've tried many types but never an assisted valve as yet.

The best results were usually valves taken from other motorcycles; Enfields, Velos, Guzzi etc. Valves fitted to cars tended to fail perhaps due to high flow/volume rate. My home made valves, well, least said the better, though a couple were acceptable. All seat of the pants stuff and a lot of fun.

I'm currently using a SX650 valve and cannot complain at all, thanks to this site.

rbt11548, I can't comment as I've no idea what the lift pressure might be or what is even in side it. The problem with a lot of fluid check valves is they usually use a very strong spring to ensure a good seal.

As long as the valve lifts at very low pressure it shouldn't do any harm. But keep an eye on it, it gets a real beating.

Cash
 
Here is the valve I made today, as I said, a scooter shop gave me a carbon fiber reed so I made the rest of the parts. Although it looks like it, I don't have that much free time, but all these parts did not cost me anything. I still have the gaskets to make. I will see how that fits on the back of the timing chest soon.

Jean

I would really like to have a proper milling machine :(

Crank case breather

Crank case breather

Crank case breather

Crank case breather

Crank case breather
 
I'm currently using a SX650 valve and cannot complain at all, thanks to this site.


Cash[/quote]

Hi Cash , any where in the UK you can by the XS650 breather valves? They look neat and small so looklike the would fit anywhere.

Cheers
Robert
 
any where in the UK you can by the XS650 breather valves?
Click to expand...

rbt,
No, I don't think there is, got mine from Germany for e13 about £7 back then when the £ was doing fine. Try this www.xs650shop.de

Jean,
Nice reed valve it looks the dogs bollocks.

Cash
 
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