Bunn Breather Kits

Hi Chaps - have any of you any experience of Bunn Crankcase Breather kits fitted to Commandos - I've Googled the subject - there seems to be some info for Royal Enfields and a few Triumphs but not much else - - any info ref suppliers in the UK ?

Cheers,

mwoo said:

Hi Chaps - have any of you any experience of Bunn Crankcase Breather kits fitted to Commandos - I've Googled the subject - there seems to be some info for Royal Enfields and a few Triumphs but not much else - - any info ref suppliers in the UK ?

Cheers,

Click to expand...

I think Norton folks tend to use less expensive solutions like PCV valves or reed valves which seem to work as well or better than the Bunn.

Bunn site
http://www.britcycle.com/products/bunnb ... er_kit.htm



Motormite site
http://www.outdoorpros.com/Prod/Dorman- ... 5/Cat/1260

If I can find that motormite here locally which end is up? I'm assuming it's a one way valve like a PCV?


Tim

A blow-suck test, but it only fits one way, half the benefit of the Motormite is it mates the 2 sizes of Cdo hoses w/o extra adapters and makes the sharp turn of rising breather hose aim naturally toward the oil tank port. Replace every few years if plastic gets decayed. Fancy ~$100 versions are made by Krane and sold to Harleys and lot and Brit vendors as well. Motormite don't knock around but the inline Al body Krane can so care to place w/o rubs or hold still.

Without being too preachy here - I have tried just about every breather set-up available on my bikes - street and race. The Motormite valve only held up for a day on my race bike (yes, I'm revving to 7k all day long - but still...), so that was useless. I never had good luck with it on my street bike either. You pay peanuts, you get monkeys.

I've tried PCV valves with steel bodies and balls inside, again with poor results. I was even given a "Krankvent", a high $$$ piece used on V-Twin bikes to install on my 850 Roadster street bike. Yes, it was really pretty, but it didn't hold up. I can blow through both ends now.

Without question the CNW breather kit works, and works well. Whenever I'm building a motor for a client, if we get down to the cases, I strongly recommend this mod. Yes, it does require machining of the cases, and I know that won't help someone who is just looking to bolt something on their existing bike. But if the time comes (winter, for example) and you want to do something wonderful to your bike, this is it. Not only does it work, it looks beautiful too.

I found the Motormite valve to work for a 100 miles or so of street riding. If have a belt drive, so it pretty easy to see if the crank seal is passing oil. I've not tried the CNW valve, but the XS 650 PCV valve is same in funtion. I've had long term excellent results with it. I will admit the CNW approach is much tidier. I understand it is more effective to mount any breather valve closer to the crankcase. Can't get any closer than CNW's setup.

JimC said:

I understand it is more effective to mount any breather valve closer to the crankcase. Can't get any closer than CNW's setup.

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This is how I have my breather valve installed, being a 72 there is already the breather on the back of the case.

Dave,

I'd be a bit concerned about the XS valve banging against the tranny. I believe it needs to be solidly mounted somewhere. Mine is mounted on the back of the air cleaner plate. Yours is, however, closer to the crankcase.

JimC said:

Dave,

I'd be a bit concerned about the XS valve banging against the tranny. I believe it needs to be solidly mounted somewhere. Mine is mounted on the back of the air cleaner plate. Yours is, however, closer to the crankcase.

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Why, do these bike vibrate or something? :mrgreen:

Yes, properly mounting the valve is on the "to do" list for this rainy season, which around here starts today and lasts until July... so I have time. :mrgreen:

But I just stuck it on there for now just to see how it'd fit and if it would work ok. From the few times I've had it running it hasn't been a problem but I did have to put in a drain hole because that close to the crankcase and you will get oil past the valve if you have the slightest wetsumping.

xs650-breather-exposed-t7345.html

When stock Combats wet sump the crank spin and cold blow by force a solid jet of oil via the breather tube back into oil tank. Check valve in Combat breather must be able to pass and withstand good amounts of oil flow for 20-30 sec or so.
If anit-sump valve keep the Combat sump mostly empty then can see an issue.

I'm bypassing iffy check valves in Peel via an exhaust extractor but poor ole Trixie Combat must retain all the original un-optimal do dads and warts or I can't feel wholesome responsible Commando owner - considering what happening to Ms Peel.

Yes past Peel had Combat oil sump modification and it worked as advertised and if anything made back up oil return even more dramatic. With Deer supplied Krank breather Peel stayed dry expect on the over rev event by dry after wards.