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Series "A" drive side ball bearing and engine build.


greg brillus

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VOC Member
Thanks Peter, getting back to the bearing housing set up, I think changing the design from the semi floating pre war verses the solid on the post war was definitely an improvement if nothing but to save wear in the steel housing, but it all means little now as they all seem to have survived this far without complete destruction. It is interesting to see the difference though. I could not compare this to the new replica twin engine I built last year on account of it running the back to back taper rollers on the drive side..........Pretty good mod at that. As for the alloy washers, I think these are aircraft parts, as I seem to remember them from years ago when we restored a couple of British planes. I think a small smear of ThreeBond on the cam box will minamise oil leaks I hope. Today I assembled the bottom end after changing the two timing side bearings, the front and rear engine plates with original finish "Black" studs and cad plated nuts and washers. I should get my act together so I can post some pics on here for you. It is coming together really nicely. Cheers.............Greg.
 

vin998

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VOC Member
VOC Forum Moderator
Greg,

My take on this relates to the expansion and contraction of the cases in an axial direction. Yes the timing side shaft is fixed, but there will need to be some give at the d/s outer main bearing to account for the expansion/contraction movement. It will try to press itself against the "tin-hat cover". If the sprocket boss, once tight, can arrest this movement to prevent the bearing pressing against the tin hat then that would be advantageous. After all, Phil put the spring there for a reason, a solid spacer might be a recipe for disaster. :eek:
Peter B
Its a few years ago, but I seem to remember when my Dad and I assembled my series A Comet, with all the bearings, shims, chip guards etc in place, the outer driveside ball bearing was pushed tight up against the outer bearing cap (tin hat). When the sprocket was tightened up you could feel it pushing against the spring between the bearings so the spring is there to allow the crank to float in this area, but also to keep pressure on the outer chip guard & washer/spacers so they all rotate and move as one and have no independent play. Bob Stafford once said that if there is too much clearance in the chip guard/shim/spacer area on the outer bearing then the primary chaincase will slowly fill up with engine oil. A sealed bearing would help with that.

Simon
 

Bill Thomas

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VOC Member
Yes, Greg, exactly as you said - but without loctite. It does need to be able to move a tad (precision engineering term) under the influence of the Thackeray washer.

I don't wish to hi-jack your question, but, while we are on the subject, does anyone know of a source of that Thackeray washer?

Peter B
Hello Peter, Long time since I have seen inside an "A", But is the washer you are talking about, Just a big flat spring washer, I have found a few odd bits over the years from when Ron left home I gave him some handle bar bits last year.
I have found a strange washer, Just under 27mm I.D. Just under 43mm O.D. Just under 2.5mm thick.
It's a long shot but I don't want any "A" bits put in the bin !. Cheers Bill.
 

Robert Watson

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VOC Member
Both my A's are converted to post war style setups on the Drive side. Obviously a new housing is required as is a new main shaft and a new sprocket. It really did simplify life in that area. On the TS the ball bearing was replaced with a roller.
 

greg brillus

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VOC Member
Hard to know what exactly is original.............Ok next question........Does anyone have any specs for the black paint used on the cast Iron cylinder head and barrel. On the post war Shadows we paint them in two pac eurothane but perhaps a heat type paint would be better on the Iron parts due to the heat they generate. I'm thinking perhaps a satin black finish rather than gloss or flat. Cheers...............Greg.
 

timetraveller

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VOC Member
Greg, over here the paint is easy to obtain. It is generally listed under 'exhaust manifold paint' and is generally used by car restorers who want to have their under bonnet car bits looking as smart as the outer body bits. It is available under a wide range of colours and can be gloss or mat finish. Some of it is listed as coming from China so it probably is available in Oz. If not then I could probably send some. I have never used any so cannot vouch for the quality but straight onto the exhaust manifolds as they come out of the cylinder heads must be a fairly severe test.
 

Dinny

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VOC Member
Looking at the factory pictures I would say they should be flat or satin finish as none look gloss to me. Probably flat. Thats what I'm going to do as gloss does not look right.

Mark
 

greg brillus

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VOC Member
Does anyone have any info about the need, or not for a copper head gasket. This one looks like it might need one, if so are any available. If not I might have to get some made, thickness.........1 mm........? Any help, many thanks...............
 

vin998

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VOC Member
VOC Forum Moderator
It appears some bikes had copper gaskets and some not. All depends upon the barrel & head been used. I have heard the barrel spigot was changed during production but what was changed exactly I don't know. When my dad & I rebuilt my bike a copper head gasket was bought from Conways, but upon assembly I measured the compression ration and with the gasket it was too low. Without it was spot on so I just ground the head to barrel joint in a similar fashion to post war and went without a gasket and its never been a problem. Sorry I cannot find the gasket to measure the thickness. I think it went in with a load of A parts to my brother.
Simon
 

davidd

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VOC Member
I sold my A twin to Scott Dell. When he rebuilt it a few years ago for the current owner he had to make some new gaskets because the person that restored the bike did away with them. He made them from some copper sheet. I believe that he had some fitting problems with the push rods and rocker positions that necessitated the gasket. You may need a dry build, as Simon did, to determine how things fit.

David
 

Dinny

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VOC Member
I have the new gasket that Simons talking about and I dont know if I need it yet. I can take some measurements off it for you and I will try and figure out if I need it. If not i can send it over to you, just give me a few days.
Mark
 

greg brillus

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VOC Member
Thanks for the replies, I will check the liner to head spigot depth to see what I can get away with. Ok my next one is probably a difficult one.........I have fully rebuilt/restored the Miller Dyno mag but the only part I am missing is the small duplex chain that drives the dynamo. Does anyone know of any available or what can be done to solve this issue. Cheers.............Greg.
 

timetraveller

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VOC Member
I'm not familiar with these bits but if all else fails then two new aluminium toothed wheels and a toothed belt might do the job. The wheels are available in a wide range of sizes, widths etc. so it should be possible to replicate and gear ratio required. These are also very cheap items these days.
 

Dinny

Well Known and Active Website User
VOC Member
I've checked the two copper head gaskets I have here, the old one is 12 thou thick and the new is 26 thou.

Looking at my head/barrel I do need a head gasket but have not had a chance to work anything out as my backs killing me!

Mark
 

greg brillus

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VOC Member
What are the general thoughts about a cylinder base gasket. Is it just a thin paper one or something else. Cheers..................Greg.
 

Don Morris

Active Website User
VOC Member
From some years ago my thinking on the large spring washers was that when you tighten up the sprocket nut , and the bearing housing, the inside of the inner bearing is pushed against the flywheel. This relieves any axial thrust on the balls in the ball race.

I found that trial assembly with the drive side bearing housing fitted to the flywheel assembly (not in the c/cases) made things easier to understand and with sprocket nut tight the bearing housing spun easily on the main shaft. I must give credit to Bob Stafford here as I do not pretend to be an expert on 'A' twins but found building mine up was an "interesting" exercise especially compared to doing the same with a 'C' twin.
 

A_HRD

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VOC Member
Welcome to the forum Don. I, for one, look forward to your Series A words of wisdom on other aspects of building and fettling your immaculate machine.

Peter B
 

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