Author Topic: What is it (breather on tappet cover?)  (Read 1936 times)

Online Triton Thrasher

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Re: What is it (breather on tappet cover?)
« Reply #45 on: 25.12. 2018 15:40 »
I know I'm being a bit simplistic, but if you use energy to compress a gas, you regain energy as it expands. So all you need is a timed breather to cope with the excess gas from piston ring blowby and the majority of air in the crankcases is just squeezing and expanding and staying almost but not quite energy neutral.
If you are pumping it continually, might you not be expending more energy?

Pressure in the crankcase makes it leak oil.

Rings need combustion chamber pressure to make them seal.  Combustion chamber pressure is the difference between pressure above the piston and pressure below the piston.

Denser air in the crankcase causes more air resistance to the moving parts (windage).

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Re: What is it (breather on tappet cover?)
« Reply #46 on: 25.12. 2018 20:15 »
All true but so I suspect are some of my observations.
2 twins, 2 singles, lots of sheep

Offline BSA_54A10

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Re: What is it (breather on tappet cover?)
« Reply #47 on: 25.12. 2018 21:22 »
I know I'm being a bit simplistic, but if you use energy to compress a gas, you regain energy as it expands. So all you need is a timed breather to cope with the excess gas from piston ring blowby and the majority of air in the crankcases is just squeezing and expanding and staying almost but not quite energy neutral.
If you are pumping it continually, might you not be expending more energy?

In the mythical engine used by schools to teach the relationship between Pressure , Volume &  Heat you would be almost correct if you ignore the heat radiated out of the engine.
In the real world not quite so.
Unless you are using total seal rings in both grooves you get leakage between the rings & the bore / piston.
So you always get gas bypassing the piston. More on the compression stroke than the other 3 .
Next pumping a fluid requires a lot less energy than compressing one.

But don't believe me .
Go to the blog and see the results form the research engines.
There are other benefits from through breathing but they are a bit on the esoteric side.

The basic problem was the original breathing system was designed to SUCK AIR INTO the engine past all of the oil slingers because they did not use seals on the crankshaft.
This gets overlooked by most people because they do not look back far enough , just at the problem as seen today.
Because BSA's were designed in the  slide rule days the methods were different and usually it was a case of using what they knew from experience worked on the previous models.
When you have a bad case of Beeseritus so play with & learn about everything from the year dot, it becomes apparent.
You see things like bore & stroke ratios that carried on from model to model, because they knew that this ratio worked and would not crack frames or set up sympathetic vibrations that sent the bike sideways at specific revolutions.

In the computer in your pocket days where almost any idiot like me can design an engine then run it without touching a piece of metal, it is difficult to appreciate the problems back in the 40's & 50's when the A7/10 was deigned  and every thing had to be thought out then made in metal to test your idea.

For BSA engine breathing was not a problem they just did what they did with the previous model, till they needed to get better performance from the B44 engine in order to hold on to the only area of motor sport where BSA was still a power thus got the results to promote sales. So the B50 got the closest thing to an adequate breather that BSA ever fitted to an engine.
The B50 engine was pumped up to the highest compression ratio that would stay together, but they needed more Hp and they got that little bit extra by the 1/2" breather.
Ten years latter Yamaha brought out the SR 500 which also used the massive 1/2 " breather to squeeze that bit extra out of the engine.
Had either of them put a timed or controlled inlet on the rocker cover they would have seen another Hp or 2 from that engine .

The easiest way to increase the Hp on an engine was to bump up the compression.
Following that was gas flow within the head so that is where all of the research went.

By the 80's EPA regulations world wide was pushing towards controlling oily gas emissions by forcing the crankcase gasses to be passed through the carb & burned so research on through breathing became a non event.
Bike Beesa
Trevor

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Re: What is it (breather on tappet cover?)
« Reply #48 on: 26.12. 2018 08:15 »
And all this reminds me of an old saying. "You can lead a horse to water but you can't make it drink".
Cheers
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Offline wortluck

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Re: What is it (breather on tappet cover?)
« Reply #49 on: 26.12. 2018 17:50 »
When I've been for a 200m ride and park up, I find oil over the bottom of the crankcases and a small puddle at the bottom of one of the centre stand legs.  I check the engine oil and it's the same level - as is the gearbox and primary.  The bike runs fine and doesn't seize up after a 'spirited' ride.  If the oil is down to the breather, surely it's doing its job and we shouldn't be worrying too much about it.  Also reassures me about why the oil is there.  Shoot me down if I'm missing something. *conf* *conf2* *doubt*

Offline BSA_54A10

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Re: What is it (breather on tappet cover?)
« Reply #50 on: 26.12. 2018 22:12 »
When I've been for a 200m ride and park up, I find oil over the bottom of the crankcases and a small puddle at the bottom of one of the centre stand legs.  I check the engine oil and it's the same level - as is the gearbox and primary.  The bike runs fine and doesn't seize up after a 'spirited' ride.  If the oil is down to the breather, surely it's doing its job and we shouldn't be worrying too much about it.  Also reassures me about why the oil is there.  Shoot me down if I'm missing something. *conf* *conf2* *doubt*

If you have been flowing the thread, you will note that the breather as fitted was described as adequate for low speeds and getting progressivly worse as engine speed rises.
If you had fitted a through breathing system, your cankcases would be clean & dry.
This is why most people fitted them, not for the performance improvement that few if any would notice or even need but to cure the "marking it's place" oil puddles left on friends drivewys.
I just park on the road or the grass verge.
Bike Beesa
Trevor

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Re: What is it (breather on tappet cover?)
« Reply #51 on: 27.12. 2018 01:28 »
AHAH now then musky 02-05-2014 horses for courses *smile*. the thing I will be needing to know is where I can get the said bunn breather or similar  from for my hopefully going to be a nutter engine for the featherybed project ,or how to improve the breathing if said bunn is extinct *eek* come on fess up who's hoarding the buns *fight*

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Re: What is it (breather on tappet cover?)
« Reply #52 on: 27.12. 2018 04:32 »
G'day berger.
Lost me on the date so I went back through my posts. Post # 3703 was that date and a link to my clubs show and a pic of my Cafe. Yes she needs to breathe.
Unfortunately the Bunn is no more. A mate was experimenting with a few bits & pieces. He found these work quite well, about 2/3 way down the page. Need 1 for in and 1 for out. http://www.hollandnortonworks.eu/en/exclusive-commando-parts
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Muskys Plunger A7

Offline BSA_54A10

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Re: What is it (breather on tappet cover?)
« Reply #53 on: 27.12. 2018 05:35 »
G'day berger.
Lost me on the date so I went back through my posts. Post # 3703 was that date and a link to my clubs show and a pic of my Cafe. Yes she needs to breathe.
Unfortunately the Bunn is no more. A mate was experimenting with a few bits & pieces. He found these work quite well, about 2/3 way down the page. Need 1 for in and 1 for out. http://www.hollandnortonworks.eu/en/exclusive-commando-parts
Cheers

Rex was doing them again, to order.
Email him
Bike Beesa
Trevor

Online Sluggo

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Re: What is it (breather on tappet cover?)
« Reply #54 on: 27.12. 2018 08:39 »
Unfortunately the Bunn is no more. A mate was experimenting with a few bits & pieces. He found these work quite well, about 2/3 way down the page. Need 1 for in and 1 for out. http://www.hollandnortonworks.eu/en/exclusive-commando-parts
Cheers

Quite right,, There is many MANY long arguments about the Bunn breathers, Seems tiring, However they did work to a degree.  But my take away whether the previous solution the infamous Motomite breather, The bunn or the other versions is no need to fixate on a "Specialty" fitting with accompanying markup.

I am all for supporting vendors, But dont get so wrapped up stepping over a penny to spend a dime.  There is a variety of breathers that work quite well and motorsports compatible without buying a Binford 1000 model.   The unit that came stock on later model HD sportsters and Buells works quite well, and used on a variety of cars and motorcycles if you cross reference the part number.  The metal one on the link Musky provided is a common variety as well and IIRC is specced for lawn mowers and Yamaha ATVs??? 

The issue was the original moto mite was a plastic unit and tended to fail from heat and oil eventually, The Bunn was better, But there is a wide variety of other units and very inexpensive. Dont know about other countries. But here in the US many autoparts stores like NAPA will let you look thru their supplier catalogs and You can find one to suit for a very common application so, No need to order a specialist part.

Norton people seem to be the most prone to that issue.  I have repeated the story many times, But the original Norton 850 starter "Assist" was a reject prestolite starter for HD sportsters but did not live up to its demands. So sold to Norton as "Good enough for a limey bike".

The solution to the anemic starter was conversion to 4 brush system and better cables and connections and battery..  Now this is well documented in HD circles and the parts are not too expensive. But Norton people seem adverse to hearing this, So they stick their fingers in their ears and say loudly "Nananana nah,,,,cant HEAR you"...  And instead pay 2-3x as much for the same bit of kit from a Norton vendor.

History repeats, The transmission on  a Norton 961 is a HD Sportster/buell 5 speed, A suzuki clutch and alternator. The starter comes on a wide variety of Harley, Buell and even John Deere, Kubota-Yanmar, and other 3 cyl diesel tractors.  You can literally buy parts for them at the local lawn & garden store.  Norton people insert their fingers in their ears, and same "nanananana nah"  I know people whos Norton 961 spent all of the summer in dealer service waiting for parts from Blighty.  A local had this problem as well and happened literally in sight of a Lawn & Garden store where I could have walked to it and sourced the parts to repair his bike with nothing more than a screw driver.  He refused, called a tow truck and few days later took the bike to Seattle to the nearest dealer 3hrs away where it sat for 4 months.

The solutions can often be close at hand and very inexpensive, Not that CNW and other shops dont appreciate your money $$$$$$$$  *thanks* But its likely NOT a zebra when you hear hoof beats in central park.
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Offline wortluck

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Re: What is it (breather on tappet cover?)
« Reply #55 on: 27.12. 2018 08:50 »
Cheers Trevor - only skimmed through this thread.  My main interest was how normal the 'puddle' was (only small) and whether it was having an effect on oil levels (which it isn't). *smile*

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Re: What is it (breather on tappet cover?)
« Reply #56 on: 27.12. 2018 09:21 »
G'day wortluck.
It doesn't take much oil to make a mess. At least not enough to show in the tang/box or primary. If you had a real accurate dip stick you might see a few ounces in the tank but that would be a BIG mess.
Two duck bills would do for road riders.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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Offline wortluck

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Re: What is it (breather on tappet cover?)
« Reply #57 on: 27.12. 2018 09:30 »
Cheers Musky - wot d'you mean by 'Two duck bills would do for road riders'?  Also, 'tang/box? - presumably gear box.  Just trying to get my head round the lingo. ;)

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Re: What is it (breather on tappet cover?)
« Reply #58 on: 27.12. 2018 09:39 »
Oops, You know what they say about a Yamaha XS650 right?  Yamaha copied a BSA and made it better???   *eek* ::hh:: *countdown*

So, Yamaha guys argue about the same topic... 5 pages,
See: http://www.xs650.com/threads/crankcase-breather.1771/page-2

So this is the common breather, MikesXS supplies them for $23
See: https://www.mikesxs.net/yamaha-xs650-reed-type-engine-breather-valve-pcv.html

But alternatives: " Yamaha YZF R 125 EGR exhaust valve, it has the pipes at 180 so it fits in a straight pipe run. (found on ebay for less than 5 pounds)

Fram PCV valve, $5.00 
See: https://www.amazon.com/FV380-Positive-Crankcase-Ventilation-Valve/dp/B000C33LK6/ref=sr_1_149?ie=UTF8&qid=1545902914&sr=8-149&keywords=PCV+crankcase+breather
Fram metal body $4.95
See: https://www.amazon.com/FV299-Positive-Crankcase-Ventilation-Valve/dp/B000C2ZJNY/ref=sr_1_152?ie=UTF8&qid=1545902995&sr=8-152&keywords=PCV+crankcase+breather
AC Delco (I use these a lot!)  $8
See: https://www.amazon.com/dp/B000C9QVD4/ref=sxbs_sxwds-stvpv2_3?pf_rd_p=6375e697-f226-4dbd-a63a-5ec697811ee1&pd_rd_wg=6qDUE&pf_rd_r=J5F9R07G20ZH38K0MTC1&pd_rd_i=B000C9QVD4&pd_rd_w=p0h76&pd_rd_r=00ffdecb-c82b-49a3-b929-bf1a16067802&ie=UTF8&qid=1545902995&sr=3
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Re: What is it (breather on tappet cover?)
« Reply #59 on: 27.12. 2018 10:24 »
G'day wortluck.
Duck bills are just a rubber hose flattened at the end. Blows out but can't suck in. Used on lots of bikes to drain airbox.
G'day Sluggo.
Yes many ways to get over the problem but tried and tested (Nortrun owners are finicky) on a mates SR/XT/TT500
Works well. Going to put them on my 76 XT500.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7