Author Topic: Bunn Breather - or something like it  (Read 6747 times)

Offline roadrocket

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Bunn Breather - or something like it
« on: 16.04. 2014 23:20 »
Hello,

The Bunn breather kits are no longer available, but you can buy a very long and expensive book that tells you how to rig every bike you like, and all the science behind. The short version can not be had via Kindle for some reason. Now, have anybody fitted one to an A10, and will they reveal which parts are needed to rig one up?

Otto in DK
Otto in Denmark

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Re: Bunn Breather - or something like it
« Reply #1 on: 17.04. 2014 12:27 »
Are you sure about that ?

Rex & I keep in touch since he went back to NZ & he has not said anyhting about stopping production , although he is now in the middle of making a movie.
He was having them made by a local factory.
Nothing special in the kits except for the valves & the material he finally settled on ( no I will not tell you what it is ) to make them out of.
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Trevor

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Re: Bunn Breather - or something like it
« Reply #2 on: 17.04. 2014 15:13 »
A friend has been trying to get one for a while and phoned Rex.I had heard he sold it off and the new owner has shelved it.
The system is so simple (the valves are a work of art and far from simple) fresh air in one way, gaseous fumes out another way.
Very light poppet or reed valves would work (just not as well).
Cheers 
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline roadrocket

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Re: Bunn Breather - or something like it
« Reply #3 on: 17.04. 2014 16:58 »
I would happily buy one, but as they are no longer available, I thought that no harm could be done by making up sometjing similar. The guidebook is not available either, except for the 600 page version which is very expensive, and not what I need.

Otto in DK
Otto in Denmark

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Re: Bunn Breather - or something like it
« Reply #4 on: 17.04. 2014 22:22 »
A friend of mine had one fitted to rocker box one to crankcase breather and the crankshaft oil seal popped out, presumably due to excess pressure caused by the crankshaft bunn breather blocking up, this was with new breathers on a newly rebuilt engine.

The oil seal popping out is a safety feature Ive been reliably informed, it is deliberately not securely held in place.

The bike now runs fine without the crankshaft breather.

So my 2 cents worth is that the (extremely extensive) theory on these breathers is probably fine, but in practice they are just another point of failure.

Maybe some engines benefit from them some don't? Maybe the engines that suffer from above average blow by?
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Offline kiwipom

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Re: Bunn Breather - or something like it
« Reply #5 on: 17.04. 2014 22:53 »
hi guys, a bit of research came up with this, cheers
...
See this this link for the Bunn breather, they are expensive £89 but have been developed specifically for motorcycles by Rex Bunn in American.

Shropshire Classic Motorcycles are the UK agents for Bunn breathers, their website is www.triumphbonneville.com/
and you need to go to the T140 Shop tab on the left of page and then put breather into the search box and it will bring it up.

mod edit. insert picture
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Re: Bunn Breather - or something like it
« Reply #6 on: 17.04. 2014 23:58 »
Here is my set up.
1: intake to front tappet cover. Nice clean cool air going in at the hottest spot of the motor.
2: exit bad air out normal exit point. Piped to oil tank. Or to atmosphere if wanted.
3: bad air enters oil tank. A std tank could be modified.
4: bad air and oil fumes exit oil tank.
5: exit to atmosphere.
The only internal mod was to cut the timed breather off at the holes so the ports are always open.
No problems like blown seals. Less oil leaks. Quicker revving. You get used to the sound of the valves.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline kiwipom

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Re: Bunn Breather - or something like it
« Reply #7 on: 18.04. 2014 01:20 »
hi guys/musky, one guy i came across made his setup from these parts from Ebay,cheers
p.s.musky,can you explain the mod to the timed breather a bit more,cheers
A10.G.Flash(cafe racer)Honda 250 vtr. Yamaha Virago XV920.

War! what is it good for?Absolutely nothing, Edwin Star.
NewZealand

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Re: Bunn Breather - or something like it
« Reply #8 on: 18.04. 2014 02:53 »
Hi this is my 1st post, I have Bunn breathers fitted to both my BSA's The A10 is a 1954 S/A basket case bought off Trade me, as it was a budget rebuild only new rings & big end bearings were fitted, on start up it breathed  as you would expect from the crankcase leaving oil leaks when ever I stopped after fitting the Bunn breathers the leak was 99% cured I fitted the inlet in the back end of the timing chest & the outlet from the rocker box. I piped the original crankcase breather with 5/16 copper tube & then plastic tubing down to terminate adjacent to the rear chain which it lubricates nicely. On consultation with Rex I tried blocking the factory crankcase breather but it over pressurised the engine on a long trip & leaked out of the head at the back by the pushrods & on to the magneto slip rings causing misfiring. I would certainly recommend these breathers as they do control oil leaks by reducing crankcase back pressure. My A10 has now done 8 thousand miles which has given this 73year Kiwi A lot of pleasure.

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Re: Bunn Breather - or something like it
« Reply #9 on: 18.04. 2014 03:39 »
The non return valve pictured would work but it would need a very light spring. The Bunn valve opens with a flea fart. I cut the timed breather off at the bottom of the holes (see pic), that way the flange and cork are still eliminating any camshaft end float, but the port is always open.

Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline kiwipom

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Re: Bunn Breather - or something like it
« Reply #10 on: 18.04. 2014 04:04 »
hi guys/Musky, thanks for the pic it explains a lot.(He spent a day or two with Rex and was able to obtain a kit) perhaps you could inform me of his add he might be just down the road then i can contact him to see if he has anymore kits. I didn't realise that the engine breathing was the cause of all the troublesome oil leaks, having now read a few articles on the subject i see that we certainly need to improve the original set up, cheers
A10.G.Flash(cafe racer)Honda 250 vtr. Yamaha Virago XV920.

War! what is it good for?Absolutely nothing, Edwin Star.
NewZealand

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Re: Bunn Breather - or something like it
« Reply #11 on: 18.04. 2014 06:52 »
kiwipom PM sent.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline scotty

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Re: Bunn Breather - or something like it
« Reply #12 on: 18.04. 2014 22:24 »
I've had the Bunn breather kit on my B33 for some time and it works a treat.
I always wondered how to fit it to the A10  and now I know*smiley4*
Thanks for the post
S

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Re: Bunn Breather - or something like it
« Reply #13 on: 19.04. 2014 01:28 »
Well I think Otto has his question answered, and at the risk of going off topic, I remember seeing that the standard timed/rotary breather could be modded to work better, by elongating the hole in it? Ive done a search but not found the details on this forum, does anyone know where the post is with the details of the mod?

One other thing that seems odd is the breather runs at half speed so if it has just one hole it must only allow gases out every other revolution, would making 2 holes in it make it work better?

Going back to the Bunn breather, a quick search reveals this a contraversial and much discussed topic for the other brands like norton triumph etc, another what oil is best what tyres are best sort of topic, here's a sample link which mentions the use of other valves from brake servos and xs650's

http://www.nortonownersclub.org/noc-chat/technical4-commando-forum/342798656/view
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Re: Bunn Breather - or something like it
« Reply #14 on: 19.04. 2014 03:08 »
G'day all.
Well the Bunn Breather is no more *ex*.
Mr Bunn sold the business/patents over a year ago and no longer has an interest in it.
From what I gather the new owner has shelved it. I will endevour to find out the new owners particulars in the hope that with enough inquires he may decide to commence production.
A friend had been working on a reed valve set up that tested as good as the Bunn. Watch this space.
Cheers 
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7