Author Topic: Timed breather, what is the actual timing?  (Read 3112 times)

Offline duTch

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Re: Timed breather, what is the actual timing?
« Reply #30 on: 25.03. 2016 01:11 »

 Hey KiwiGF, did you sort it?

 I just heading out the door and had a thought while pondering my own, that if the filter in the bottom of the sump maybe blocked or too fine a mesh, may inhibit oil drainage and a buildup in the main chest?
   Maybe a bit far fetched, but if there's still an issue might be worth a look if not already discounted?

       *dunno*
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Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #31 on: 27.03. 2016 22:39 »
Hi,

I tried to reply last night but it didn't appear. Maybe because I didn't put a long enough time to stay logged in. I am the guy who's A10 this is all about. I have now done an intro.
Status now:-
- Took on board BSA_54A10's points about valve guides with gapless. I am proposing to take my head to our local reconditioners. They say they can do K-liners if they can fit the jig in there. I will try to do both exhaust and inlet. My valves were sloppy in their guides. I also believe my smoking is on the overrun, more. I apologize - my gapless set has no steel rings.
The breather I got from Rocket Racer, thanks - is the same in all respects (later-model version, with taper not step). However, the peg hole is a bit further round to the right of the first breather hole. This would make it open and close a bit later. These all have the same part number 67987. Mine opens at 90 degrees btdc - which is the only timing specification I have gleaned from the forum. So, I propose to stick with that.

Online KiwiGF

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Re: Timed breather, what is the actual timing?
« Reply #32 on: 28.03. 2016 09:08 »
Hi Scott any chance you could do your "find the breather timing trick"  *yeah* using Tim's breather?

So the forum has a record of the difference?

To me it's very odd *eek* there is difference between two parts with the same number, and given they spin at half engine speed a few degrees difference in the peg location might make quite a difference  to the timing  *dunno* but whether that significantly affects the breathers operation *dunno*
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Offline Rocket Racer

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Re: Timed breather, what is the actual timing?
« Reply #33 on: 28.03. 2016 21:25 »
They say they can do K-liners if they can fit the jig in there. I will try to do both exhaust and inlet. My valves were sloppy in their guides.

We're moving onto a new topic here but I'm sure I have been warned off using K liners on aircooled motors (in my alloy heads) by several people in the past (5 years back??) ... cannot recall the details and may be quite mistaken.

But while a bit of smoke isnt doing much harm, money spent on a poor repair is heart breaking.

Please do some further research before going down that path
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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Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #34 on: 28.03. 2016 22:31 »
Hi KiwiGF and Rocket Racer,

Yes, I can do my timing trick on the other breather and let you know.
As regards K-liners, our engineer was ok with them  but had 2 provisos:-
- the clearances can't be as tight as car engines, for that very reason - ours are air-cooled engines, get hotter and the valves seize
- you have to support the guides top and bottom when you put the liners in, otherwise they split
I checked with the reconditioners and they can do them in cast-iron guides (as mine are) in an iron head, as long as they can fit the jig. I will make sure they know those provisos above.

Regards

Offline BSA_54A10

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Re: Timed breather, what is the actual timing?
« Reply #35 on: 29.03. 2016 11:37 »
K liners seem to be fine in the inlets but a bit dubious in the exhausts,
By now they should have worked out good running clearences but there were quite a few failures early on.
Bike Beesa
Trevor

Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #36 on: 19.06. 2016 23:29 »
I need to follow up on this thread after having the k-liners installed.

The suspected excess clearance beforehand was verified by inspection. The inlets were about 3.5 thou". There was some confusion about the exhausts. The reconditioner thought one valve had worn 3 thou" but when we measured it when it was left over after the head was back together with a new one -  it was standard. I didn't get exact before measurements for exhausts therefore, but I believe they were sloppy. There was a lot of black deposit up both. He thinks that was evidence of pressure escaping up there - a suspected factor in crankcase pressure.

Anyway, we agreed on clearances with k-liners of: 1.5 thou" inlet; 2.5 thou" exhaust. He was pleased with his success after we had to order new inlet guides because one cracked. One other thing I did to mitigate crankcase pressure is to extend the holes in the timed breather valve. These were Dremelled out to the right (with hole on top) - according to the guidance in Roger Sharman's article. This makes them 12mm in length. They would open a bit earlier therefore and not allow as much pressure buildup on the downstroke. I know I can't isolate this from the k-liner effect, but I hope one of these measures will stop the drive-side seal blowing out. (The cork breather is good and compressed).

So the bike now runs very nicely. It is the best performance I have experienced with it. However, it still smokes a bit...I have measured the oil consumption and it is back to 1 pint in 200 miles. This is the best I have ever had but it's not good. This pint-in-200 is a standard that "one shouldn't worry if it was no worse than", apparently. I followed Jay on our ride back from Makara yesterday. He swapped onto the A10. The puffs were intermittent and alternate between left and right. They seemed to be when he revved after slowing down, what you call the "overrun" - which still suggests oil down the valve guides to me?

Anyway I will just run with this and see if the drive-side seal stays in place. The next step if it doesn't is a rebore. Remember I have the Total Seal gapless ring set. I have my old 8.5 to one comp pistons (BSA?). The clearance wasn't too big there apparently, but my engineer thinks there's a "scratch in one bore" where it rusted during years of sitting. This wasn't removed totally by the last honing apparently (about 2k miles ago). I think these rings have bedded in. They are supposed to "compensate for engine wear". I didn't get valve stem seals put in because this may have "starved the oil supply" a bit. They seem to be meant to compensate for wear too but we thought unnecessary with the k-liners. Total Seal do recommend seals.

I'm hoping that the remaining oil consumption isn't associated with factors that still might cause excess crankcase pressure (like piston blowby). If so, I'll just live with a bit of occasional smoke for now.

Thanks for listening and all the help so far...

Online Peter in Aus

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Re: Timed breather, what is the actual timing?
« Reply #37 on: 20.06. 2016 10:42 »
Hi Scott & Jay, if you still have trouble with drive side seal coming out could try this (see pic) you have to make a small grove in the front bolt post just make sure you don't go right through to the hole, it is made out of about 1.5mm plate, I have done this on my 58 A10 and is working fine.
Peter

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Offline muskrat

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Re: Timed breather, what is the actual timing?
« Reply #38 on: 20.06. 2016 11:32 »
Nice workaround Peter. Now do yourself a favor and drill and lockwire those two screws.
Cheers
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Online Peter in Aus

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Re: Timed breather, what is the actual timing?
« Reply #39 on: 20.06. 2016 12:38 »
Yes Musky I have done that, I should have mentioned that *good3*

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Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #40 on: 30.01. 2017 22:40 »
Hi all,

I was encouraged to revive this thread by Anjimehra's issue (which is the opposite way round). I think I'd like to restrict the oil flow to the inlet rockers a tad. So, to recap:-
- I have a Total Seal Gapless ring set (just cast iron)
- I put K-liners in the valve guides - with tighter clearances than standard (2 1/2 thou" exhaust; 1 1/2 thou" inlet)
- this seems to have cured the crankcase pressure that kept blowing out the drive side oil seal (exhaust guide clearances were too high)
- the K-liners have caused no trouble after about 500 miles. The bike is going really well
I was discouraged by the reconditioner from putting seals in the inlet valve guides, against BSAA10_54's advice. I think my high oil consumption (pint in 190 miles) is from oil still being sucked (by the gapless rings), down the guides and burning . My own observation and others' following me seems to be the smoke puffs are on the "overrun". So, my question is - as at least an interim measure, do think there's any problem narrowing the rocker banjo inlet bolt hole down to 1mm (from the current, standard, 3/64" - which is same as exhaust one)?

Regards to all

Offline BSA_54A10

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Re: Timed breather, what is the actual timing?
« Reply #41 on: 31.01. 2017 10:44 »
None what so ever.
When I first started riding we would pinch off the return line to get more oil up the top where all us 15 year old "experts" knew it was needed.
By the time I was 18 the pinched off return tubes had been replaced & we were pinching off the rocker feed and drilling out the oil return holes.
The gapless rings put a lot more load on the breather and in the long run you would be better off going full flow through breathing.
The problem is air has mass so there fore there is a latiency in its movements.
The std BSA breather is only timed right to around 3000 rpm and from there on it gets further out of sync with the gas pressure pulses in the sump.
At certain speeds, it starts to work backwards.
Rex found this out when researching engine breathing and that is why he went to a through flow system rather than trying to create & maintain  low pressure in the crankcases.
This idea dates back to the earliest days of motorcycling when engines had no oil seals so you were sucking in through all of the scrolls and blowing out through the breather.
When oil seals were fitted every where, the same breathing systems were kept on and they have been failing ever since.

What was most important to BSA was the engines appeared oil tight in the dealers showrooms so all of the breather systems used is biased towards the lower engine revs.
Bike Beesa
Trevor

Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #42 on: 31.01. 2017 20:34 »
Thanks very much again, for your help on this..

Offline Scott and Jay

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Re: Timed breather, what is the actual timing?
« Reply #43 on: 11.03. 2017 20:46 »
The story continues.. I found the same symptom - of oil over the back wheel, after some hard riding on the way up to the rally. The upshot is that the drive side crankcase seal hadn't been forced out this time. The crankcase pressure was all handled by the breather valve as timed. This is where the oil must have come from - out the exit pipe. So, I just have excess piston blowby - despite the gapless rings. The oil gets black pretty quickly. I was going through over a litre in 200 miles. I can't get any of those nice +80 Wiseco Pistons and rings from Cake Street. Roger has gone out of these now. I am finalising a set of pistons and rings from AdrianW (member and IDC Piston proprietor) - together with the liners to sleeve back to standard...

Online Superflash

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Re: Timed breather, what is the actual timing?
« Reply #44 on: 23.02. 2020 05:43 »
Gents. Resurrecting a fairly old thread here, however I've been reading through a lot of the past posts about this subject trying to understand how it all works from a practical side of things. I understand the theory of having a breather etc, I'm just struggling with how it all actually works. Example....the breather itself sits on a peg located on the cam pinion. A cork spacer is used to get the cam end float to where it needs to be. the 2 holes in the breather will line up with the 2 holes in the inner timing case as it spins, thus allowing the expulsion of pressurised air.....right....got all that. 2 things have left me baffled though. is it only the inner timing case hole that the breather slides into, all that stops it falling off the cam pinion pin? And secondly, the inner timing case has 2 holes...one leads upwards and appears to vent into a hole in the main case. The other leads down, and presumably out of the case? I ask this last question because the tube leading downwards has been plugged. Should it be, and do I need to drill it out to create a clear pathway for escaping gases? Cheers
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