The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Peter Gee on 11.07. 2019 19:08

Title: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Peter Gee on 11.07. 2019 19:08
I have seen a few folks fit a gooseneck pipe and extension  rubber pipe to the breather exit on the drive side c/case outlet, but it seems it was not the practise from the factory. I am soon to start my 59 A7SS rebuild, and although I intuit that the BSA breather system  is novel compared to other twins, I can't see why I won't get  at best an oily mist exiting from the breather outlet, blowback of the same at speed and a general mess?

Enlightenment awaits me, I hope.
Title: Re: Ignorance : Why Do A10/A7 engines have no breather pipe?
Post by: Swarfcut on 11.07. 2019 20:04
Pete, for what it's worth an evolution of design and cost cutting.  A7 Longstroke and the early Plunger cases share the same breather external pipe, depositing oil mist onto the chain (via a small bleed hole) and onto the road and garage floor as the pipe was originally secured to an engine through stud behind the sump plate. Late Plunger engines have a small pipe directing breather mist to the gearbox sprocket, anchored beneath the flat alloy  extension/chainguard front mount.

 With the advent of the S/A engine, some retain the same type of early pipe, exiting down by the sump plate, later ones just have a hole, presumably as the engines could be fitted in frames with a fully enclosed chaincase and the pipe would be in the way. The oil mist lubricates the fixed front chainguard section, which is why many survive.....or because lots were removed.

 Your option is to enjoy the oil and muck of yesteryear or counterbore the hole for a spigot and add a flexible pipe to allow oil mist to lubricate the chain or  just drip.

 Swarfy.
Title: Re: Ignorance : Why Do A10/A7 engines have no breather pipe?
Post by: Peter Gee on 12.07. 2019 08:38
Thank you Swarfy, however, am I correct the location of the breather outlet is: drive side crankcase, below the boss that is for the non-driven end cam journal? If you reach down with a finger just   the primary chaincase  "gap" with the crankcase, you can feel  the hole?

If so it takes a standard BSP copper pipe..perhaps with a dab of JB weld..one could add a little  spigot. Have not yet started the engine so it should be fine and dry  to take the JB Weld. Thanks again

Title: Re: Ignorance : Why Do A10/A7 engines have no breather pipe?
Post by: Swarfcut on 12.07. 2019 09:05
Pete, yes, that's the one. The hole is a shade over 8mm diameter and runs straight up towards the cam bush for 65/70mm.  Any tube introduced into the hole will obviously offer a restriction. A thin walled tube may be too flimsy to survive the engine vibration, hence a suggestion to counterbore  for a spigot, which allows the original 8mm bore to be maintained.  But sod that, JB Weld and a  beer can sleeve as a quick experimental remedy? A steel roll pin would also do if you can find one. Maybe I am a bit cautious about restricting the hole...a copper tube was originally used, just sealed into the hole and well supported, this proved adequate at the time. Plenty of pictures on the Forum to show how other folks have modified the outlet to catch the drips.

 Swarfy.
Title: Re: Ignorance : Why Do A10/A7 engines have no breather pipe?
Post by: Greybeard on 12.07. 2019 12:00
Peter, why are you worried about the breather. It seems to do fine the way it is on most of these engines. The position of the outlet does give the chain a drink.
Title: Re: Ignorance : Why Do A10/A7 engines have no breather pipe?
Post by: Peter Gee on 12.07. 2019 16:22
Greybeard, because the outlet of the breather is simply a hole in the back of the drive side crankcase. Ig hot oil mist is coming out of it, it will give many more parts of the bike a drink IMO.  Not having had an A7/A10 before, I simply don't know how that arrangement of a plain hole behaves when under way.

Every bike I have ever owned besides a japanese total loss had a breather pipe going down under the bike....this is exactly what someone has done here
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Greybeard on 12.07. 2019 19:15
My engine does have a pipe stub in that hole. It's pointing toward the drive sprocket.

If the engine is in good order and if it's not ridden like it's stolen, the breather will not produce much, if any, oil.

I am not aware of anything coming from the breather on my bike; there is no sign of oil dripping from that area after any length of ride. I actually need to lube the chain once in a while.

Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: mugwump on 12.07. 2019 21:02
I've owned many cars from the 1960's and a crankcase breather pipe open to the elements was the norm. Trouble was the burnt oil residue tended to enter the car though!
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Peter Gee on 12.07. 2019 21:04
GREYBEARD: That you have zero oil coming out of that breather hole is very interesting. It shows the BSA design was excellent compared to many. I think I will install a gooseneck copper pipe anyway..with rubber hose..this is a concours rebuild and nothing like a few drops of oil to lose one a prize, after a lot of hard work.

On another matter I indeed fitted the sandwich old Payen head gasket from the batch I have.. amazing how much re-torquing they need.. always a bolt of two looser.Have not of course run it..am going to retorque ver the next few days till these is no more give in any of the 9 bolts before I do. I hate messing with rocker boxes!  Enjoy the weekend.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: trevinoz on 13.07. 2019 00:57
It is a good idea to fit a tube into the breather outlet, especially when starting with a full sump.
Without a tube, oil goes everywhere, with a tube it can be directed into a container.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Swarfcut on 13.07. 2019 08:19
Pete, I see you have found the earlier thread about the breather. Apologies for repeating myself here, but while I thought it familiar, I had forgotton  my contribution to that thread.  Looks to be the start of "Maturity Onset Aytentia,"** one of the classic symptoms. I reckon you folks can list a few more of this affliction, enough to start a new topic.

 Trev.. A timely reminder to reach for the big bowl when you find the oil tank empty and you can't be arsed to drain the sump.

Swarfy.

 ** Aytentia... A state of mind brought about by too much attention to other folks A10 Problems......A10 (Demen)tia.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: BSA_54A10 on 13.07. 2019 14:27
If you get your hands on period publications you will see that the tube used to fall out and get messed up in the chain.
The plain hole does not do this.
Also unlike the Japanese engines this breather is timed so apart from reversion nothing goes into the hole
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: RogerSB on 13.07. 2019 18:26
1960 A10 - no pipe (photo taken using a small inspection mirror).
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: trevinoz on 13.07. 2019 23:06
Swarfy, no bowl is big enough and the stand gets in the way.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: berger on 14.07. 2019 13:31
if your unlucky like I was and its wet sumped enough you don't only get it all over the floor but also blown past the maggy seal and an oil cooled mag is the result *eek*
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: worntorn on 12.08. 2019 14:53
Now I know why my enclosed chain always looks freshly oiled when I peer through the inspection hole!
Also, next day after a 50-100 mile run there might be a few drops of oil coming from the bottom of the chain case joint at the rear sprocket.
No need for an O or X ring chain on this bike. Road grit can't get at the chain and the crankcase breather keeps things nicely oiled. The chain will last a long time.

Glen
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: trevinoz on 12.08. 2019 23:01
Glen, how does oil get into your enclosed chain? If I am reading this correctly, you have a fully enclosed rear chain.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: worntorn on 13.08. 2019 00:52
Looks to be a tube fitted into the breather hole , then a short bit of rubber hose and an elbow thru a hole in the chain case.
I guess all modifications by some previous owner?
It seems to do the job!

Glen
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: bikerbob on 13.08. 2019 09:30
Worntorn the oil may not be coming from the breather pipe, I have an A7 which has a fully enclosed chaincase which at times leaks the odd drop of oil from one of the drain holes in the bottom section. My bike does not have a pipe from the breather to the chaincase like yours and the chain always seems well oiled, so the oil in my case I believe is coming from the back of the gearbox leaking along the main shaft and running down the sprocket lubricating the chain then dripping into the chaincase. This is a job that I intend doing over the winter lay up SRM supply a sprocket nut with an oil seal that helps prevent this type of leak. I am a bit surprised to have this leak as when I overhauled the gearbox a couple of years ago I replaced the bushes in the constant mesh gear.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: morris on 14.08. 2019 22:34
Worntorn the oil may not be coming from the breather pipe, I have an A7 which has a fully enclosed chaincase which at times leaks the odd drop of oil from one of the drain holes in the bottom section. My bike does not have a pipe from the breather to the chaincase like yours and the chain always seems well oiled, so the oil in my case I believe is coming from the back of the gearbox leaking along the main shaft and running down the sprocket lubricating the chain then dripping into the chaincase. This is a job that I intend doing over the winter lay up SRM supply a sprocket nut with an oil seal that helps prevent this type of leak. I am a bit surprised to have this leak as when I overhauled the gearbox a couple of years ago I replaced the bushes in the constant mesh gear.
I had the same issue on the SA. In spite of changing the bush, with minimum shaft tolerance, it still leaked.
The SRM nut cured that completely.
For the record, the nut won't fit a plunger engine/gearbox though. Not enough space between primary case and sprocket.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: duTch on 15.08. 2019 09:34

 wornie and b-bob, have a sniff of the drips; g-box/tranny oil has a distinctive aromatic effect on your olfactory senses- as you are probably aware but forgot to mention  *beer*


 
Quote
......For the record, the nut won't fit a plunger engine/gearbox though. Not enough space between primary case and sprocket.

 That's really handy info, thanks- I had wondered  *good3*
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: JulianS on 15.08. 2019 09:41
Some sprocket splines are a poor fit on the constant mesh gear splines and oil seeps along them and drips onto the chain.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: muskrat on 16.08. 2019 10:55
G'day fellas.
I always put a good dob of silastic in the sprocket splines. The new nut from SRM also works well. Had one for years made locally.
O ring chains and heavy duty chains (our bikes only produce 40HP) may be too wide and rub on the case, and rob valuable power.
Cheers
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: bikerbob on 16.08. 2019 11:03
Thanks for those tips Julian and Muskrat will have a look when stripped down over the winter.
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: muskrat on 16.08. 2019 11:05
Wots winter???  *roll*
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: bsa-bill on 16.08. 2019 11:19
Quote
Wots winter???

in the UK anytime before and after the random week of  sunshine *sad2*
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Peter Gee on 29.08. 2019 23:22
Interesting I have run my rebuild now for like 20 miles....I added a breather pipe stub and a pipe exiting below the gearbox....no oil drop  from this feature so far.

Never seen the like of it in decades of Brit builds! :-)
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Sluggo on 31.08. 2019 11:13
The topic of breathers comes up from time to time.  The truth is, for most people who motor about gently its not as much of a problem but truth is the stock breathers are woefully inadequate and contribute greatly to oil leaks.   This can be tested on any engine easily enough, But the Norton people seem to take the obsession to the next level.  However real results have proven that improved breather systems, especially with a check valve does improve performance as well as eliminating oil leakage.

Especially on a long stroke vertical twin, Uncorking it and then measuring the sheer volume of air going in and out, will show this.  There is also a correlation between pressure and volume, as in, the greater the capacity, the less the pressure exerts force.  Triumph, and late BSA engines tried to exploit this by sharing crank case pressure into the primary and then venting with a much larger pipe.

Ideally, the best system was developed by a clever fellow in Wisconsin named Erik Buell.  Other designs have since followed suit, But this can work on a British Vertical twin as well Although on some models the passage to the crank case is constricted via the pushrod chamber, But the attch picture shows the concept,

Used to be much press on a design called the BUNN BREATHER, and the ideas have evolved, what was relevant was if its possible (And proper check valves can make that happen) going from positive, to neutral and then ideally to negative pressure can really benefit any motor, especially long rod twins. (lots of huffing and puffing)

So what are the benefits?
A) Oil leakages will almost be eliminated
B) Slight boost in power
C) less oil fouling and contamination, as the rings seal better under a negative pressure.

Now,,, a modern Automotive LS motor is a total universe removed from these old engine, the benefits are measurable and demonstrable.  However, percentage wise may not seem worth it.

Horses for courses. 

However this article, which just came out demonstrates this concept quite well.  Many of the guys running vintage race bikes are using these same techniques, and guys like Herb Becker, and Alp are proving it at the track while racing 1950s and 60s vintage Britt Iron.

See: https://www.enginelabs.com/news/efi-university-finds-out-how-much-power-a-dry-sump-system-is-worth/?utm_source=rss&utm_medium=rss&utm_campaign=efi-university-finds-out-how-much-power-a-dry-sump-system-is-worth

"  “From 3,000 rpm to 6,000 rpm, on average, the engine made 17 lb-ft more torque and 14 horsepower more… Everywhere. Some places made more than that, some made a little less, but there was an increase everywhere.”

In addition to power, Strader also recorded crankcase pressure on the dyno pulls to be able to illustrate how hard the scavenge pumps are working. “We had no pan vacuum with the wet-sump system all the way across [the RPM range],” says Strader. “With the dry-sump, we had about 6.5 inches of vacuum at 3,000 rpm, and by the time we got to 6,000 rpm, we had almost 10 inches of crankcase vacuum in the engine. That improves the ring seal and helps with the windage, and that’s where that extra power came from.”
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Peter Gee on 01.09. 2019 20:46
Amazing stats above! Whodathot it?
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Sluggo on 06.09. 2019 02:25
I cited the engine tech article as it proves a point, and while the main point was comparing a wet sump vs a dry sump system it indirectly proves my point about drawing a negative pressure (VACUUM) and how that aids ring seal and performance.  It shows as well, that inadequate breathing is rather counter productive both from a performance perspective as well as oil leakage.

While it should be obvious,, the engine in that Dyno testing I linked to is a LS based auto engine and the performance specs clearly in scale are impressive but you wouldnt see those numbers on a 500 or 650cc engine, but scaled to application, you WOULD see results. 

2 schools of thought always seem to endure. 

A) Pipe smoking tweed jacket types who insist 1940s and 50s technology is the top of the game and no reason to change.  AKA Factory knows best.

B) Those who enjoy optimizing old technology while enjoying the character of these old steeds.

Neither are really wrong, Horses for courses,, but at least acknowledge they exist. *smile*
Title: Re: Ignorance : PHOTO ADDED Why A10/A7 engines have no breather pipe?
Post by: Greybeard on 06.09. 2019 08:33
I cited the engine tech article as it proves a point, and while the main point was comparing a wet sump vs a dry sump system it indirectly proves my point about drawing a negative pressure (VACUUM) and how that aids ring seal and performance.  It shows as well, that inadequate breathing is rather counter productive both from a performance perspective as well as oil leakage.

While it should be obvious,, the engine in that Dyno testing I linked to is a LS based auto engine and the performance specs clearly in scale are impressive but you wouldnt see those numbers on a 500 or 650cc engine, but scaled to application, you WOULD see results. 

2 schools of thought always seem to endure. 

A) Pipe smoking tweed jacket types who insist 1940s and 50s technology is the top of the game and no reason to change.  AKA Factory knows best.

B) Those who enjoy optimizing old technology while enjoying the character of these old steeds.

Neither are really wrong, Horses for courses,, but at least acknowledge they exist. *smile*

C) Pipe smoking tweed jacket types who accept 1940s and 50s technology and see no reason to change it. Maybe add an oil filter....and an electronic voltage regululator...and LED bulbs.

https://goo.gl/cS6cDf