Author Topic: Bunn Breather - or something like it  (Read 6761 times)

Online muskrat

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Re: Bunn Breather - or something like it
« Reply #30 on: 02.05. 2014 21:25 »
Trevor, your preaching to the converted. I KNOW it works, and works well.

Yes TT, we Aussies do have a different sort of sense of humor. The one that comes to mind is "you can lead a horse to water but you can't make it drink". I have one fitted to my cafe and wish I had more kits for my other bikes. I noticed the difference the moment I fitted it by having to back off the idle. Throttle response is much quicker and less oil leaks.
Lets just agree to disagree.
Cheers   
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Re: Bunn Breather - or something like it
« Reply #31 on: 03.05. 2014 10:27 »
I have little faith in the "full explanation."

Large breathers, with or without one-way valves, are well known to reduce oil leaks.

 The desirability of drawing fresh air through the engine sounds like superstition. Why would I want cold Scottish fog to enter my engine?

Mr Bunn appears to be ploughing a lonely furrow if he purports that a partial vacuum in the crankcase reduces power.

Well he and the engineering school at the University of Auckland where the latter work was done and a couple of graduate thesis would all have to be wrong as well.
Please do not tell HD as they modified their engines and AFAIK rex is still getting royalties for that work.
 
Have a look under the hood of most Mitsubishi's.
At the rear of the engine in the rocker cover is a pipe from 1/2 to 3/4 on latter models which is plumbed into the air cleaner.
This is the fresh filtered air inlet.
Near the distributor is another line usually 1/2 with a one way valve in it which goes to the carburettor or to the engine side of the butterfly on fuel injected engines.
This is the crancase exhaust
Clean air in , dirty air out.
So if Mitsubishi went to this extent on a partially balanced engine pumping system, are they just superstitious ?
They are however not 360 deg engines like a single or Pommie twin so the flow characteristics are totally different and they can get away without a valve on the intake.


When Phil Irvine developed the Repco Brabham "Yella Terra" engine one of the things he did was to add a fresh air intake and a valve regulated exhaust.
GMH fitted this engine ( minus the big cam & domed pistons ) to the 1966 range of cars.
The full Yella Terra kit came with a new PCV valve and rocker air inlet designed to work properly at the higher revs that these engine did comparred to the standard red series engines.
I know this one as I fitted a head without the modified breathers and it was as smokey as hell under full throttle till I got the right breathers on it.

Oh and Phil did this after he had a stint at Chamberlan Tractors where he doubled the Hp of their entire range ( both petrol & deisel ) and these all got fitted with flow through crank case ventilation as part of the upgrade.

Now perhaps this was because we have high energy air down here comparred to your lazy fog up there, but some how I think not.
Bike Beesa
Trevor

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Re: Bunn Breather - or something like it
« Reply #32 on: 03.05. 2014 11:19 »
Interesting stuff, thanks.

I can see how a through flow of air might clear nasty gases away and that must keep the oil and cases cleaner, to some extent. I suppose the inlet is restrictive, to maintain depression in the crankcase? 

I wouldn't set much store by what modern car makers do. They have emissions priorities.

My own old bike has no oil seal on the drive end of the crankshaft, so I don't expect much air would come in through an inlet on the rocker cover. I've driven a few miles with a screw-on rocker cap missing and didn't notice any better performance or throttle response.

There is an oil seal on the timing end of the crankshaft and the acids and gases have failed miserably to destroy it, over many years.




Online Triton Thrasher

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Re: Bunn Breather - or something like it
« Reply #33 on: 03.05. 2014 14:12 »
Here's a rocker cover, into which clean fresh air passes, in a cold damp climate.



It suddenly occurs to me that I have not looked inside a car rocker cover since the 1980s. Motoring is not what it used to be.

Offline roadrocket

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Re: Bunn Breather - or something like it
« Reply #34 on: 20.05. 2014 20:26 »
OK folks; I have now got one of the original kits for the T140, and will adapt this to suit the A10. At least the valves are the right ones. Thanks for all input.
Otto in Denmark

Offline duTch

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Re: Bunn Breather - or something like it
« Reply #35 on: 20.05. 2014 22:34 »

 
Quote
GMH fitted this engine ( minus the big cam & domed pistons ) to the 1966 range of cars.
The full Yella Terra kit came with a new PCV valve and rocker air inlet designed to work properly at the higher revs that these engine did comparred to the standard red series engines.

  Wow- then that was likely in the Brabham (RIP Jack) Toranas too, I think the only one I saw was parked out front of my aunts' house in Melbourne about then.....!   *eek*
 Thanks for all the input guys

 I had thought about this while rebuilding mine, so might also work towards similar mod... sometime
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline olev

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Re: Bunn Breather - or something like it
« Reply #36 on: 22.05. 2014 13:02 »
Not too sure about that Brabham torana, Dutch.
My mate had one. It had a small 4 cylinder engine that wouldn't pull the skin off a custard.
It did have a racing stripe though. woo hoo.
Don't think that's the motor Trev is talking about. I'm surprised Jack 'rip' put his name on such a piece of sh!t.
cheers

oops, hope you're not passionate about them.

Offline duTch

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Re: Bunn Breather - or something like it
« Reply #37 on: 23.05. 2014 00:00 »
 Haha Yep Olev, I'm hearin' yea, would say it put the tard in custard- the one I saw was (custurd) yellow with a black stripe maybe your mates, don't imagine they made many- but if any still exist I'm sure it'd be a collectable (but you wouldn't tell anyone...!!)

  Well that's that Yella Terra done and dusted...!   *work* *beer*

  Related, but not Bunn or engine Primary case- As an experiment the other day I fitted an old finned inspection/ filler cover to the primary so I could undo it easy when hot, to allow hot (expanded) air out to maybe alleviate pressure/oil leakage...? Will have to see if it makes a difference- just a thought
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

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Re: Bunn Breather - or something like it
« Reply #38 on: 23.05. 2014 07:50 »
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

I run bunn breathers on Bender and have adopted the opposite approach to Muskrat  *eek* although otherwise comparable. I vent to a breather bottle on the sidecar deck
My fresh air comes in the original breather and fresh is vented out the top front rocker box. My philosophy for the 10cents its worth is that I want the fumes being blown topside not down through the engine as my engine fumes are carrying methanol, which I don't want dwelling in the bottom end where they can encourage corrosion.
I think the bunn breathers are ideal for any racing application, but probably unnecessary for a plodder.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Re: Bunn Breather - or something like it
« Reply #39 on: 23.05. 2014 11:41 »
Not too sure about that Brabham torana, Dutch.
My mate had one. It had a small 4 cylinder engine that wouldn't pull the skin off a custard.
It did have a racing stripe though. woo hoo.
Don't think that's the motor Trev is talking about. I'm surprised Jack 'rip' put his name on such a piece of sh!t.
cheers

oops, hope you're not passionate about them.

The Repco Brabham ran what became the Holden red motor which was superceeded twice if not 3 times before the Torana saw the light of day.
Despite the bull shit that is being spread every where the deal was Repco footed the bill for the car ( if not all , a good lump of it ) in return for the technology and endorsements from Jack.
After Jack did the deed Repco released the engine pack in drips & drabs as did Ford with the Moffat ( phase I, II & III uprades ) Falcon motor.
These were marketed as Yella Terra, starting with just the cam ( useless ), head with cam, head cam & extractors, and full kit head cam coil distributor extractors induction tube & breather.
I am not quite sure if the "red" motor came before or after the Repco Brabham and Phil Irvine is uncharasticlly vague about the exact timing apart from the fact he was commissioned to work on the old Holden "Grey" motor ( 138 from memory ) and his work principally turned it into the "red" series ( 149 & 176 ?).
Repco continued to offer the hot up kits for the reds and for the blue series that followed.

Cerdit where credit is due, Jack was a really really good driver, but that Repco Brabham was such a good car it was around for nearly 20 years and was winning for at least 10 of them without Jack in the hot seat.
As for lending his name to the Torana, Jack was never one to turn down a job or say no to a cheque.
He was the "named front man" for the bunch of "criminals" who milked the state government mercilessly building the original white elephant called Eastern Creek Raceway.
Which from memory was a quick & dirty land grab from the bod who got framed for the Hilton bombing ( his name & the sect name eludes me at the moment ).
Bike Beesa
Trevor

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Re: Bunn Breather - or something like it
« Reply #40 on: 10.07. 2014 03:26 »
Just a quick heads up.
It appears that there wil be a limited production run of the breather kits very soon for the US distributor only.
So if you want one put an order in now.
Looks like there might be a new manufacturer early in the new year, solicitors pending.
Bike Beesa
Trevor

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Re: Bunn Breather - or something like it
« Reply #41 on: 10.07. 2014 04:42 »
Just a quick heads up.
It appears that there wil be a limited production run of the breather kits very soon for the US distributor only.
So if you want one put an order in now.
Looks like there might be a new manufacturer early in the new year, solicitors pending.

Trevor,
 do you have any contact details for the distributor?
Cheers
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Re: Bunn Breather - or something like it
« Reply #42 on: 11.07. 2014 10:53 »
British Cycle Supply Company
Bike Beesa
Trevor