The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: groily on 13.11. 2012 17:28

Title: Bottom end saga
Post by: groily on 13.11. 2012 17:28
I mentioned in passing a few weeks back that after a lot of miles, my A was getting a bit of attention, mainly in the drive side roller department  . . .
Well, as folk know, nothing is ever as straightforward as it ought to be.
It started with a slipping clutch.
After 50K km or more without even looking at it, not surprising really, so it was meant to be a simple case of adjust it, get some new springs and/or some friction plates and away we'd go.
With the primary off, though, 'twas obvious there was too much float on the crank. The shock absorber nut had backed off a bit, and in fact the lobes of the cams were jammed peak-to-peak. And there was close to a millimetre of float. Aaargh!
So, this simple clutch job got instantly more difficult. Always a pain when something is running apparently perfectly, but no escape.
With the crank out, it was clear the inner race wasn't tight on the mainshaft, and the shims had been taking a hammering (although they were intact luckily, nothing nasty in the cases or the oil).
The ends were excellent at -30 and the timing side bush was remarkably good. Not trusting my measuring sticks, I made a plug and progressively shrunk it without de-chucking till it would go in - which it did, at one thou over the journal's dimensions. Seemed round as well, and parallel, but that was something for those with better measuring sticks to prove or disprove.
So I sent the crank to T&L Engineering, whom I use frequently for my AMC twins and regard very highly.
Verdict was swift - yup, 'drive side mainshaft is undersize, and the thrust face on the crank web has been worn down a bit over the years, we'll sort it with metal spray and we'll probably avoid the need for any shimming'. That was where I was at when I posted something on a thread about metal-spray a while back.

Well, all seemed well, and the crank was returned looking good, complete with rods' eyes checked for ovality (both fine), ends confirmed to be virtually unworn and timing side journal and bush as being round and parallel and with a clearance of no more than 1.5 thou. Nice. Sa
So I put it together. Seemed good. New cam followers just because, new oil pump drive and spindle just because, and a few sundry bits, like rings (I'm lucky to have original BSA marked +1mm pistons and I want them to do every mile they can) and a valve guide here and exhaust valves there, with a view to getting a whole load more miles out of the motor. Oh, and some Surflex clutch plates. Thanks to C&D Autos and to British Only Austria for the various bits, delivered fast and efficiently.
Started first kick  . . .  but there were 2 problems.
The first was weird - no oil return but loads of delivery as the diminishing tank showed. This proved to be very lucky.  STOP engine.
Lucky because the second problem was that the cage of the new roller had picked up on the new metal on the crank's thrust face and ripped off a few bits which were sitting ominously in the gauze thing at the bottom. Really ucky, because if there had been an oil return I'd have ridden off on it and probably wrecked the whole thing.

So, out comes the crank again, to see what the shards of metal are all about - and they are as described above.
T&L were very good about it, and immediately offered to do whatever it would take - which would be to clean off the excess new material and basically start again, using a hard shim if necessary.
So back goes the crank, while I figure out that there's meant to be a transverse pin in the scavenge pipe that stops the ball being sucked up the oil pump nearly - but my pin just wasn't there. Must have disappeared a zillion miles ago, and luckily the ball had previously stayed at the sucky end and not gone all the way up to close off the return.

And in next to no time, back comes the crank . . . .

Yesterday it went back in and all the boring stuff was done - engine in, transmission etc etc - and today I kicked it. First prod again (this bike always has started just like that), and instant oil return this time as I'd wound the crank by hand for long enough on the bench to prime the crank gallery and the bearings and get enough oil into the cases for the scavenge to be seen to be working before proceeding.

So a quick 40km to see all was well, and yup, same as ever.
But what a palaver.

If there's a moral to the tale, it is probably that I am reverting to my old position on metal-spraying - which is Don't!
Bit of a pain to have to pull the motor twice etc, but it's all good practice I suppose  . . . and all's(eems) well that ends well as the engine has run for an hour or more today. No lumps in the slime, no funny noises, just the same as it was before the clutch started to slip and the story began. Bit more compression, and of course the state of the guts is now known to me. For this was a bargain basement bike of unknown provenance, on which in 5 years or more I'd only ground-in the valves, made a new sleeve gear bush, fixed the electrics and bought cheapo clutch plates. Can't be bad.

Now to see whether it'll do another 50K km or more without any serious hassle  . . . .
Title: Re: Bottom end saga
Post by: RichardL on 13.11. 2012 19:26
Great story, Groily, thanks for spitting it out. One thing I didn' catch, wht did T&L do the second time. Spray? Shim? Other?

Richard L.
Title: Re: Bottom end saga
Post by: groily on 13.11. 2012 21:44
Ha! Good Q Richard.
They machined the new metal off the thrust face (crank web) while leaving it on the shaft (which was undersize before), and made up a single thickish hardened shim. Ie did it the 'normal' way. Makes me believe the 'metal-spray' poster who said building up on non-load bearing bits is one thing, but on parts that take a whacking, less good?
I reckon, FWIW, there'd (maybe) have been no problem if the extra metal's diameter had been confined to the od of the inner race only rather than going wider, as this would have left the cage with space behind. But I really don't know. I'd post pix of the consequences of the first failed effort if the pic limit here was a bit larger (hint)! Not pretty anyway, especially given the engine ran for under 90 seconds before I killed it.
BTW, the bearing I had in there before was a FAG with the cage and rollers held in the outer race; the new one is a Japanese NSK from C&D with the rollers contained in a steel cage between 2 lips on the inner. C&D say they've sold close to 500 of these rollers and no probs, so I was happy. But, the older design offered far greater roller contact area than the new one. Some might say 'good', remember what happened to Nortons and Bonnies before the barrel-roller Superblensds came in (like what I've got in my P11's Atlas engine), but part of me says the greater the contact area the better. We'll find out over the next gazillion miles of use and abuse!
Cheers, Bill
Title: Re: Bottom end saga
Post by: olev on 15.11. 2012 10:42
Gday Groily,
Do you have the NSK bearing number handy?
NSK make some interesting bearings.
I'm wondering if its one of their specials.
Title: Re: Bottom end saga
Post by: groily on 15.11. 2012 12:00
Hello Olev,
'fraid I don't know for sure as it's in there now (and I hope it's darn well staying there this time!), but it is the bearing C&D Autos sell as their stock replacement. A 'C' clearance 206 I guess, with steel cage and balls on the inner race between lips. C&D's web site is under reconstruction at the moment so can't see what they sell (if they ever specify in that detail), but they've sold a few hundred of them without, they say, any bad news.
Sorry not to be more use!
Title: Re: Bottom end saga
Post by: A10Boy on 15.11. 2012 15:54
I guess that reinforces the negative opinion on metal spraying cranks, sometimes it works and sometimes it doesn't. I trust T&L 100% in what they say and do. Bad luck anyway.
I tend to think that the roller can be a nice sliding fit on the crank [but not loose] as that helps with shimming and as long as the cush nut is tightened to 65 Flbs the inner will be held tight to the web and can't turn.
Anyway, hope you get another 50,000 out of her.


Title: Re: Bottom end saga
Post by: RichardL on 15.11. 2012 17:38
So, is there a method for crank refurbishment wherein new material is welded on the journals with, say, aerospace quality that gan be ground and heat treated to like-new specications? Would doing this cost more than building a plant to manufacture new BSAs?

Richard L.

P.S. Who you callin' a "bottom-end sagga' "?
Title: Re: Bottom end saga
Post by: groily on 15.11. 2012 19:11
Reckon it does Andy, despite my earlier optimism.
Not faulting Derrick at T&L in any way as he couldn't have been more helpful - just a pita to have to strip the engine like that again. But talk about being darned lucky to have lost the oil return for a separate (and so improbable) reason  - I'd never otherwise have known what was going on till it was way too late, because the engine sounded great. As it was, nothing metallic got as far as the pump, let alone into the feed side. Live and Learn is about all there is to it really. At least my inner race is a modest press fit rather than a sloppy slide, and with those 65ft lbs on the nut (now I've made a serious weapon to do the standard BSA one up easily) it should hopefully hang together.

Richard, I just don't know. But others will of course. If pressed, I'd still have journals built up I think if there was no alternative, but I'm very much back where I was thirty years ago on the whole topic and will try to avoid any more risky/clever ideas.

Probably ought to start thinking about sourcing a spare crank as I'm on -30 as I mentioned, but not sure what the limit is on the undersizes.

Being forthright, it starts to become a balance between active riding life expectancy on the one hand and mileage aspirations on the other! By the time the faculties have weakened, the docility of my best-beloved B31 may be all I can cope with  . . .

Title: Re: Bottom end saga
Post by: morris on 15.11. 2012 22:14
So, is there a method for crank refurbishment wherein new material is welded on the journals with, say, aerospace quality that gan be ground and heat treated to like-new specications? Would doing this cost more than building a plant to manufacture new BSAs?

I know a bloke who makes a living out of this kind of work. They even do metal loading and welding on helicopter shafts and engine parts.
They do plasma and high frequency welding and some other forms of black magic on metal.
I use them regularly to do metal loading on our printing presses, when for instance some dumb-ass operator dropped a spanner or a screw into the machine and thus damaged the impression cylinders.
Also stuff like copper inking rollers, where the copper has worn away, they make 'em better as new
Up till now, I have never heard them say "nope, this can't be done"
I already discussed with him about metal loading on crankshafts and stuff, and he says that for them it's no problem at all. They can go up to any required grade of hardness and tolerance
Can't give information about prices right now, but next time I speak to the guy, I will ask him, and let you know.

Title: Re: Bottom end saga
Post by: A10Boy on 16.11. 2012 09:41
Bill, those SRM cush nuts are the dogs. They have a hex to take a socket and are easy to tighten with a decent length torque wrench.
Title: Re: Bottom end saga
Post by: groily on 16.11. 2012 10:42
I do agree Andy, I saw one one time - but my weapon's pretty OK, fits well and made of 2 inch bar with an inch an' a 'alf hex milled on to take a serious 3/4" drive socket. Quite pleased with it actually (it's a bit like a bigger and 4-pegged version of the weapon used to get the clutch operating arm correctly aligned and locked tight on AMC gearboxes - another challenge I know we're well familiar with!)
BTW, how do folk hold the crank still? I lock things with a length of old primary chain - not against the inner chaincase! - is there a better option?
Next time, I will definitely get the SRM nut though, as it's obviously THE answer. Maybe it also makes it easier to fit the split-pin too? That would be good as it's a bit of a fiddle poking about down in the dimple if one wants to fit a chunky pin that is close to the dia of the 'ole in the mainshaft.
Ah well, done for now. Fit and forget for a good while I hope!
Cheers, Bill
Title: Re: Bottom end saga
Post by: A10Boy on 16.11. 2012 14:18
I use a chain too. The problem is though that it still tries to turn on the cush lobes, but they seem to click off at 65lbs OK

Title: Re: Bottom end saga
Post by: chaterlea25 on 16.11. 2012 21:05
Hi All,
I use a clutch locking tool with a handle that comes to rest on the bike bench or whatever to hold the crank while tightening the crank and clutch nuts
I bolted a plain and friction plate together with two of the bolts about 2 1/2in apart or so,  some spacers about 1/2 in. and then a long handle onto the bolts as well, this places the handle to one side of the clutch so as the nut can be accesed
The one slight downside to th SRM nut is that the hex is quite shallow  *ex*
One some sockets theres quite a lead into the actual hex or bihex , these sockets need to be faced off so as the socket will grip the nut enough

I use thread locking fluid on the threads and have never had one come loose using it
The lock tab is a pain in the ar*e as they tend to tear just as the final tightening is happening

My 2 cents worrth

Title: Re: Bottom end saga
Post by: edboy on 20.11. 2012 18:24
i remember in the mid eighties there was a guy fom ilford who was having worn large journal cranks built up to std using submerged arc welding process from some industrial place in east london. sorry i cant remember where but my crank cost me £50 and he must have sold loads more as he was autojumbling.
Title: Re: Bottom end saga
Post by: Housewiz on 03.12. 2012 01:55
Hey John,

Post some photos of the tools made for this project?  I saw a clutch locking tool on the web with tabs on both the inner and outer edges.  Is this what you made by bolting together a friction and pressure plate?