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Discussion Starter · #1 ·
Has anyone got any pictures or good ideas about triumph 650 rocker box breathers ? I have always struggled to get the top ends oil tight on triumphs and think breathers might help.
 

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There's no crankcase pressure up there, hence no need for breathers.

If you've got leaks it's because the surfaces aren't flat, the gaskets are no good (cheap stock paper gaskets) or you're using a poor sealant.

Check that all surfaces are flat, smooth and clean. Then wipe with lacquer thinner to remove all oil, then apply a thin film of Yamabond (or Hondabond) to the head surfaces only.

If you've got leaks from the inspection caps, use new stock gaskets but apply grease to both surfaces before installing them. Or make your own gaskets from cork gasket material (that's what I do), or use 0-rings with a light coating of grease.

Nothing makes a Triumph engine builder look sillier than breathers on the rocker boxes!
BSA's however will benefit from a rocker box breather because there is crankcase pressure there.
 

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Glider, No crankcase pressure up there? Put down the bottle and back away from the keyboard.How do you think the oil from the rockerboxes gets back down to the sump? Down the pushrod tubes thru holes in the tappet blocks and you are in the crankcase. Now the reason most triumph engine builders don't relieve the pressure at the rockerbox is you would then have air(pressure) trying to go up thru the holes in the tappet block at the same time oil is trying to drain down thru the same holes. Pretty much a conflict of interest. There are better ways and places to relieve c/c pressure,rockerboxs are used because they are easy,not good. Jack
 

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Discussion Starter · #4 ·
Forgive me but i was under the impression that the scavange side of the oil pump was of larger capacity then the feed side, this means this side of the pump for some of its time is pumping air along the return oil line and so air gets to the rocker boxes, no ? This means the rocker boxes are pressurized with air, its this air i want to vent , but i am looking for a neat and tidy solution.

The gasket surfaces have been lapped on a surface plate and are flat, i will be using copper gaskets, but these surfaces are narrow and i think any pressure is enough to force out oil.
 

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Bon, the return side of the pump is larger,that is true, but only slightly,and it dumps into your oil tank with only enough restriction to back some of the oil up to the rockers.I've had clear line on a rocker feed before and never saw enough air in the line to say it was significant. The pressure in your rockerboxes is Crankcase Pressure. It is the same pressure everywhere inside the motor that is connected to the c/c. Relieve it one place, it is relieved everywhere. The notion that air from the return side of the oil pump is causing leaks at your rockerboxes is IMHO wrong. Jack
 

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Discussion Starter · #6 ·
Bon, the return side of the pump is larger,that is true, but only slightly,and it dumps into your oil tank with only enough restriction to back some of the oil up to the rockers.I've had clear line on a rocker feed before and never saw enough air in the line to say it was significant. The pressure in your rockerboxes is Crankcase Pressure. It is the same pressure everywhere inside the motor that is connected to the c/c. Relieve it one place, it is relieved everywhere. The notion that air from the return side of the oil pump is causing leaks at your rockerboxes is IMHO wrong. Jack
Thanks jack , i haven't built the engine yet , just working on the various bits and want to get it right first time and not have to rework anything, i wonder does the oil passing through the tappet block holes cause an obstruction to air passing down into the crankcase ? I will plumb in a couple of small hosetails in the rocker box caps and link them up to the main crankcase breather.
 

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Bon, Haven't built the engine yet? That changes everything, if you want to do it right, research one-way valves. If plumbed correctly,you can get neg. c/c pressure and that equals less leaks and more power.It may not be much in the power increase,but every bit helps and it's "free". Jack
 

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Okay Jack, you got me. I know the oil gets down there through a couple of little holes in the tappet blocks, so there is some connection between the boxes and the crankcase, but we all know that there's very little pressure up there and that if the boxes are leaking it's usually due to other causes.
I wonder if putting breathers up there and allowing pressure to flow up through the tappet blocks might hinder the oil flowing downwards?

+1 on the one-way valves. Modifying the engine to breathe through the primary, like the later models, also makes a big difference.
 

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At some point in my motors life it got what looks like a reed poked into the front rocker. It does breath cuz oil mists up on my frame. But I still have rocker leaks.
 

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Discussion Starter · #10 ·
Sorry everyone i should have been clearer , its a pre-unit alternator engine , as i will be running an alternator i welded a points housing into the timing cover because i want to run a boyer ignition , so i have the space normally taken up by the magneto to play with, i was going to mount the oil filter here but don't see why a breather can't be taken from here too.

Thanks.
 

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How do you think the oil from the rockerboxes gets back down to the sump?
Gravity..

The narrower rocker feed line branching off the return line forces oil to rockers and oil falls back down to the sump through the tappet blocks..

If the rocker boxes aren't sealed air tight, you think the oil won't make it back to the sump?
 

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Ha haa^^ dude.my B/W photo above is a 1982 T140es. Now i know mt reed is factory. Cool.
 

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Triumph changed the breather system in 78 (T-140E) to a "closed" system. The frame(oil tank) was vented to the EX. rockerbox,which in turn is connected to the sump,which is connected to the primary,and the primary is no longer vented right to the atmosphere but instead go to the airbox so fumes can be drawn into the motor to be burned. Jack
 

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Plenty of pre-units and a bunch of units I have seen have breathers on the timing covers in addition to the crankcase breather window behind the intake cam. Breathers are good, crankcase pressure is high and top end pressure is a fact of life. You might also consider the following: Drill larger holes in the tappet blocks, drill holes and add breather pipes to the rocker box inspection caps (I do one exhaust and one intake on my Bonneville Salt Flats racer). Make sure you have a hose off of the actual crankcase breather stub and vent that pipe to atmosphere or somehwere else that has a bigger capacity (primary or oil tank), but remember on unit bikes the crankcase breather was loopped up around the back fender and vented to atmosphere. If you can get your breather above the engine it works better, because air can get past the oil in the pipe with minimal puke.
 

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Discussion Starter · #17 ·
Bon, Haven't built the engine yet? That changes everything, if you want to do it right, research one-way valves. If plumbed correctly,you can get neg. c/c pressure and that equals less leaks and more power.It may not be much in the power increase,but every bit helps and it's "free". Jack
Thanks for the helpful replies everyone. Jack is there a specific valve i should be looking out for ? A commonly available one from a car or truck or machine or something ?
 

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Bon,Google "Mike's XS". I've found their "reed type PVC valve" works great and is very well built for the money. The part # is 15-0677. Jack
 

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I love a good Triumph Breather thread,
I agree with Scott, the Bunnbreather Blog is a great resource.
I know some people disagree with his pricing, but he is actively funding and researching breathing for road and race classic motorcycles in a big way so I guess that costs coin, and I think you have to respect that.
 
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