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#886922 07/30/22 8:13 pm
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I’ve found a loose drive side crank bearing in my B44…

Has anyone seen a reference for the crank bearing interference fit in the crankcase or the design bore diameter? Even for an engine with a similar configuration, just to see where the engineers heads were at?

I’m looking for factory numbers, not to reverse engineer this.

Thanks
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The only reference in the workshop manual that I could find was the bearing size 25x62x17 mm. Same for the timing side. How loose is it? Would it be possible that a wrong size bearing was installed? You could heat the timing side case and press out the timing side bearing, let the case cool and measure. Since they are both the same size you would then have your bore spec.

If you don't have a workshop manual here is a link: https://www.bsaunitsingles.com/Archives/Owners_Manuals/B44,%20B25,%20C25%20Series%201967%20Workshop%20Manual%20%2000-4136%20x.pdf

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Originally Posted by Chris Johnson
I’m looking for factory numbers, not to reverse engineer this.
I can almost answer your question, but with factory data for pre-unit singles. BSA Service Sheet 304 as well as a Gold Star Maintenance manual both say heating the case in boiling water probably will release the bearing when the crankcase is dropped on the workbench, although it might need to be tapped out with a drift if that doesn't work. Since both the Al and steel will be at 212 ℉ this means the proper interference fit at room temperature can be calculated from the differential thermal expansion of Al and steel:

2" × 6×10–6 in/in.℉ × 142 ℉ = 0.0017"

I don't know the OD of your B44 bearing, and in the above I assumed 2" OD. If your bearing actually is, say, 2.5" OD, the necessary interference would be 2.5/2×0.0017"=0.0021".

But, a question for you is, what instruments do you have to measure the ID of the hole, and the OD of the bearing, to an accuracy of no worse than ~±0.0002"?

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I’m working with .0001” reading mics & bore gage and am seeing +0.0005” at room temperature. Someone fit a ball bearing on the drive side… I’m thinking the crankcase expansion caused the outer race to drag in and out over time, damaging the fit. The as-found bearing slipped out on disassembly and the replacement roller can be pushed at least halfway in with light finger pressure.

Standard bearing fit tables give a fit of +0.0004/-0.0008” for steel housings and just a note that alloy housings may require a tighter fit (making an educated guess for a K7 fit class and assuming the recommended fit is at operating temperature).

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You might already know this but, if not, don't be tempted to use Loctite. It can't deal with the repeated cycles of differential thermal expansion. Although I've never used them for this application, you might look into 0.010"-thick Speedi-sleeves to see if they, along with machining, could be the magic bullet you need.

[Linked Image]

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I’m leaning toward having the race nickel + copper plated, hopefully along with a pile of other decorative plating. I don’t expect any sort of accuracy from the plating shop but I’d like to know if I’m in the ballpark.

A Speedo-sleeve on the bearing race isn’t a bad idea. I don’t trust myself to hit the bore diameter with such tight tolerances.

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You won't be far out using a thou per inch of bore in ally.

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Originally Posted by Chris Johnson
I’m leaning toward having the race nickel + copper plated, hopefully along with a pile of other decorative plating.
Decorative plating will be much too thin. Plating to the required thickness (i.e. ~0.002") is something you can do yourself, but there are precautions to take to avoid hydrogen embrittlement. See the following two posts:

https://www.britbike.com/forums/ubbthreads.php/topics/722738/re-1928-ariel-model-c#Post722738

https://www.britbike.com/forums/ubbthreads.php/topics/723030/re-1928-ariel-model-c#Post723030

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Hi Chris and MM,
MM if you remember the fit of the copper plated bearing in your Ariel did not survive the Cannonball ??
I wonder if grinding hard chroming the bearing would work?
While working on a 38 Rudge I was trying to overcome the same problem a while ago. I had a bearing ground and plasma sprayed but the adhesion failed while machining to size !!
The "cure" was to have a bearing ground to the oversize needed by Vintage Bearings in UK, somewhat expensive for a B44 ?
It might be easier to source another set of crankcases?

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I have measured many case bores (even NOS) on these old bikes

I have found .001" - .0015" press fit for bearings

Last edited by C.B.S; 08/01/22 8:00 pm.
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Originally Posted by chaterlea25
MM if you remember the fit of the copper plated bearing in your Ariel did not survive the Cannonball ??
It's important to remember that the fit didn't survive, but as the photograph of the bearing shows, the plating did. In other words, the plating was robust.but the case was not. The hammering from the crankshaft enlarged the hole. It did not remove the plating.

Assumg B44 cases are stronger than the ones on a 1928 Ariel, Cu plating would be fine.

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Originally Posted by Magnetoman
Originally Posted by chaterlea25
MM if you remember the fit of the copper plated bearing in your Ariel did not survive the Cannonball ??
It's important to remember that the fit didn't survive, but as the photograph of the bearing shows, the plating did. In other words, the plating was robust.but the case was not. The hammering from the crankshaft enlarged the hole. It did not remove the plating.

Assumg B44 cases are stronger than the ones on a 1928 Ariel, Cu plating would be fine.

I seem to remember the plating failed under the area shadowed by the cathode wire , used around the middle of the bearing race
... which could account for Less overall interference area ... but maybe not enough to matter ?

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I didn’t want to reverse engineer this, but using the 212 degree number for the bearings to drop out (about 0.0005” clearance), I come up with about a 0.0015” interference at room temp which agrees with CBS.

The local plater is familiar with this sort of work so I’ll probably have them do it in copper or nickel/copper to add 0.002” (adding in the current clearance fit).

Getting further into the engine I found the roller on the timing side… I’ll drop that race today and see how the bore measures.

Ignorance is bliss… I shouldn’t have dug this deep.

Chris

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"Ignorance is bliss… I shouldn’t have dug this deep"
hmmmm I have been waiting for more learned minds than mine to comment, but I cannot help but think "does it bloody matter?"

Given that you can only push it in around half way before it becomes tight, is that tight enough?

Did you measure the bearing to see if the issue, if it actually exists, is there and not the casing? These bearings aren't exactly tight in the first place.
What were the symptoms in the running bike that made you look at the bearing? if the answer is none, then the answer to the question of what to do about it has just answered itself!

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Blown base gasket (again) prompted modification to B50 breathing, while first revealing some light piston seize, then the loose drive side bearing, now also an egg shaped timing side crank bearing bore (0.000” in X, -0.002” in Y), and finally a very loose (+0.0025”) main shaft high gear bearing bore.

Poor engine. Time to get creative.

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The easy solution is another set of cases and not so hard a find. I gave a set away when I parted with my last B44.

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Originally Posted by Chris Johnson
Blown base gasket (again) prompted modification to B50 breathing, while first revealing some light piston seize, then the loose drive side bearing, now also an egg shaped timing side crank bearing bore (0.000” in X, -0.002” in Y), and finally a very loose (+0.0025”) main shaft high gear bearing bore.

Poor engine. Time to get creative.

Chris
Well that told me!
yep I agree with Mr Mike, time for new cases at a minimum. The "light piston seize" would also have me worried, the slightly loose drive side bearing seems to be the least of your worries!
"poor engine" I agree, what has happened to the little thing? no oil?

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Lol but it’s numbers matching!

High compression, too much timing, round barrel, every trail is a steep uphill from home, high ambient temps… it all adds up. The previous piston had a more painful death, this one’s practically new still… new rings, more clearance, no problem.

Chris

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Don't let the nay-sayers wear you down. Repair of the main bearing housing is hardly a reason to toss out a case, even if it weren't numbers matching. Plus, you'd still have to machine the top to get the "new" case aligned with the old one.

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Both halves need help. I might try the Speedi-sleeves at this point.

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GEt it measured very carefully to see exactly how much wear is in the cases before you start , particulalry the furthest from the crank axis
It could be a case of machining to take a differnt bearing


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One effect of living somewhat remotely as I do, "readily available" isn't a thing, . Attending "swap meets" would be a tad pointless as I own the only B44s in the country. Here we are forced to actually repair things. This means we have people who CAN actually repair things. The machine shops here, would weld up the holes then re machine new ones. Although they rarely work on ancient bikes, beat up wrecks of cars that elsewhere would have been long consigned to the wrecker's yard are their daily fodder so consequently not only are they well versed in this kind of work, they are also very cheap. I would expect to pay perhaps $75us for this work. Our nation has a population of less that 100,000 yet we have at least 4 shops that would do the work. I suspect in more "civilized", disposable, regions finding someone who is both experienced and cheap could be challenging.
My previous statements of "time for new cases" was said partially in envy .... I wouldn't, and didn't have the option!

I am somewhat intrigued though as to why both bearing housings are screwed ........ could the crank be out of true?

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Tell ya what i did.......... driveside roller Main A65 loose on brg OD ..... i got some suitable bronze shim ( probably around 0.002" ) and cut 3 strips length of brg outer race thickness ,,(maybe 12-14 wide), bent a 90 degree return on them , help them in place 120 degrees apart with just a drop of locktie ... refitted the brg outer and proceeded to run it like that for 40k ? miles and counting.

nothing as good as a temporary fix that works ....

sure you can shag around doing the definitive repair, whilst debating microns, or you can spend nothing and hold the outer firmly


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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Loctite 620 bearing mount might work in a pinch, rated well enough to consider especially with Ignoramus's shims (if it blows after 10,000 miles, then rebuild with better shims) 450 F rating (for an indeterminate time). About $20 US. No guarantee it will work. Sometimes if baling wire gets me home... Plus if you just putt about for smokes. No full throttle standing starts, no hill climb record attempts or what not.. Drive like I do. Drive like gran ma etc. No expectation of a concourse trophy. Just an old putt. LOL

A bearing is available .5 mm OD oversize. A fairly easy machinist job on the timing side since one axis is .000 out.in relation to the existing bearing. The drive side should not be too hard to align since .0005 is about there any how. A good machinist will check alignment with both cases bolted together. Dave martin's comment about the possibility of the crank being untrue is an easy machinist check. All of course assuming a real machinist is doing the work with the training, experience and tools. A worn arbor will make things worse, right? If you want to kick a lot of sand, then no loctite.

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Half a thou?
You're havin' a laugh if you think a single dowel and half a dozen bolts
will hold two sand cast ally cases within half a thou.
That's why line boring etc is only an idealism. Once you've taken them
apart a couple of thou is more realistic.

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