Author Topic: Breathing problems?  (Read 575 times)

Offline KeithJ

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Breathing problems?
« on: 07.10. 2016 11:05 »
Thought I'd breath some new life in to this topic. 
I have just rebuilt my A10 engine, "all new parts" pistons, guides, conrods, roller main conversion etc and have done about 200 miles or so.  The engine goes very well and am chuffed with it.  However, on my latest run oil was coming out of the timing cover gasket.  Thought the gasket had just leaked but no, it looks OK.  Then saw oil in the dynamo drive space, should have been dry as it has a toothed belt drive.  So it looks to me I am getting too much pressure in the crank case.  I am only using the "standard timed breather".

Good thing is, it is not leaking anywhere else!

Reading other posts it appears there are different variants of the timed breather ending up with part number 67-0987.  is this so?  If so, what are the differences and how can they be identified?  It may be I have a plunger one fitted in my S/A engine.

Also, what is the ideal time for the breath to open and close and is there a "simple" way to check?  I can't get to the opening at the back of the engine below the cam shaft as I have the electric start bits in the way.

Here's hoping.

ATB
'59 A10RR + Second engine

Online chaterlea25

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Re: Breathing problems?
« Reply #1 on: 07.10. 2016 13:31 »
Hi Keith,
There have been similar cases to yours when the bush fitted to the dynamo drive on the inner case had the spiral groove cut the "wrong direction" pulling oil into the dynamo drive compartment
I think that the oil leaked out at the dynamo to timing case joint and ran down the outside ??
Did you fit a cork or felt washer behind the dynamo drive pulley? sometimes there's not room for one
The case can be modified to fit an oil seal if needed
SRM advise putting grease in the belt compartment to aid cooling of the belt
I have done some with and some without, all are good so far though

On the breather, can you rock the breather sleeve on its peg with finger pressure?
If so then the cork washer is not thick enough

John
1961 Super Rocket
1963 RGS (ongoing)

Offline KeithJ

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Re: Breathing problems?
« Reply #2 on: 07.10. 2016 13:45 »
Hi, there is some radial movement on the peg but no end float.  Surely if no radial movement is critical, then also the position the breather ends up in is also?  i.e. if there is slop between the peg and the drive hole in the breather, should it be in the fully "advance or retarded" position?  Yes, will fit a thicker cork washer anyway.

Note the comment regarding grease in the dynamo drive chamber.  Will review how it wears but I did not get it form SRM.

ATB

K
'59 A10RR + Second engine

Offline Scott and Jay

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Re: Breathing problems?
« Reply #3 on: 11.10. 2016 02:01 »
Hi Keith,

I posted a while ago about my breathing problems. I picked up somewhere that the latest breather (same part you listed) opens at 90 degrees after tdc. That is what mine did. I found out by blowing through the hole in the breather valve. I had a degree wheel on the crankshaft. I then found that it closed again at 45 degrees after bdc. I think this is standard. I had another breather, supposedly the same part, sent to me, though. This opened later than mine. I have since made a mod that was recommended in an article by Roger Sharman of Cake Street Classics. This was to open up both holes, to the right, looking from the top - by 10mm. This probably makes it open at about 65 after tdc. I cleared out the breather pathways. I have a thick cork gasket that you can't shift (on the valuable play on the peg), by hand - with inner timing cover on.
It all goes well now. A bit of oil comes out the breather tube, which I collect in a bottle. That wasn't happening before, though - and crankcase pressure was building so the drive side seal would blow out. These mods happened at the same time as I put K-liners in the valve guides to cut that blow-by right down, though. So, I don't exactly know what is the main cause of the improvement.

Offline KeithJ

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Re: Breathing problems?
« Reply #4 on: 11.10. 2016 08:56 »
Interesting, I have also have fitted liners to the guides so not sure what that does to the pressure.  I guess the peg and hole really should be a size fit as the position will affect the breather opening.
ATB

K
'59 A10RR + Second engine

Online chaterlea25

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Re: Breathing problems?
« Reply #5 on: 11.10. 2016 12:44 »
Hi All,
I have seen too many problems with guide liners in aircooled engines to use them *warn*

New guides should reduce crankcase pressure not increase it ????

As has been said if the engine is in good condition the standard breather is fine in my experience

John
1961 Super Rocket
1963 RGS (ongoing)

Online bsa-bill

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Re: Breathing problems?
« Reply #6 on: 11.10. 2016 13:44 »
Quote
There have been similar cases to yours when the bush fitted to the dynamo drive on the inner case had the spiral groove cut the "wrong direction" pulling oil into the dynamo drive compartment

OH YES, this I am guilty of, my fault entirely, replaced both bushes (taking them both out together before replacing) and subsequently replaced them the wrong way around, first indication was a timing case leak which I traced to the dynamo housing, was running an SRM belt at the time and it worked in the chamber full of oil.
This was a while ago before the advent of cameras in phones obviously.
There now I feel much better for the admission  *yeah*
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco