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of the connecting rod, and the crankshaft turns smoothly.

According to myriad "classic" magazine articles, all should be good, right?

Well, perhaps not.

I somehow got conned into becoming less and less semi-retired "just t help get this project over the line", which put me well short of Shaun's 2 hours a day in the workshop.

Nevertheless, some progress is occurring on the plunger BSA 350.

With the gearbox apart and most new parts ordered, it seemed like a good idea to split the cases to see what parts might be needed there, and also to make a decent batch to warm up to free bearings.

The first indication that all may not be well in the state of Denmark was the lack of a key for the oil pump drive/timong gear drive mainsheet pinion.

Tapping the cases apart, the next 'gotcha' was the big-end nut tab washer (last pic, but it was supposed to be first)

Removing the drive side crankcase from the crankshaft (or vice versa) revelaed the next less than ideal components.
(remaining pictures)

IMG_0672.jpeg IMG_0669.jpeg IMG_0670.jpeg IMG_0671.jpeg
Last edited by Shane in Oz; 11/06/21 7:42 am.
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The bearings may have rotated smoothly because they had been packed with grease. That's a good thing for wheel bearings, but possibly not for crankshaft main bearings.
Anyway, a new set from Mike Reillyshould get things on track.
Mike had most pf the other parts as well, which is rather convenient. I'm still short the screws for the tab washers.

The greater concern at present is the rather dubious drive side roller bearing outer race having shifted in the case while separating the case and crankshaft.

The bearings are now out of the cases, which gives me an opportunity to attempt Magnetoman's 0.0001" measurement accuracy for the housings, to try to gauge the amount of interference which may still be there.

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Originally Posted by Shane in Oz
The bearings may have rotated smoothly because they had been packed with grease.
That reminds me of the reputed old-fashioned fix for a noisy car transmission, of packing it with some sawdust.

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Originally Posted by Magnetoman
the reputed old-fashioned fix for a noisy car transmission, of packing it with some sawdust.
I always thought that was diffs, and usually the province of used car dealers such as Arfur Daley

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Originally Posted by Shane in Oz
Originally Posted by Magnetoman
..............some sawdust.
used car dealers.............
Banana peels.

But seriously, some PO might have been "preserving" old parts. And speaking of old parts, I probably have one of those lock plate screws hidden away somewhere, lock plate too. Let me know if you have trouble turning one up.

Last edited by Stuart Kirk; 11/07/21 2:59 am. Reason: Thought of something else.
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Originally Posted by Stuart Kirk
Originally Posted by Shane in Oz
Originally Posted by Magnetoman
..............some sawdust.
used car dealers.............
Banana peels.

But seriously, some PO might have been "preserving" old parts.
I don't think there was any skullduggery involved, at least by the seller. The bloke I bought it from was a car collector who had some nice Vintage and post-Vintage machines, His late father-in-law had been into bikes rather than cars, and he was liquidating the small collection. From memory, they were mostly late pre-War and early post-War ex-race bikes, all of which seemed to have seen a lot of race miles.

Originally Posted by Stuart Kirk
And speaking of old parts, I probably have one of those lock plate screws hidden away somewhere, lock plate too. Let me know if you have trouble turning one up.
Thanks for the kind offer. There were a lot of pre-unit BSA singles, so I don't think they'll be too hard to come by.

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I'm not sure where this fits in the greater scheme of things, but the primary chain case mounting face of the drive side crankcase is somewhat less than flat, so it seemed like a good idea to clean it up.

Anyway, the inner crankcase was checked for flatness on a surface plate - seems good.
Clamping the case down on the milling table and checking the chain case mounting face with a dial indicator, apart from the lumps and bumps which prompted the exercise, the face seems to be around 1mm out of parallel with the inner face. That doesn't seem quite ideal for chain case mounting.

It rained all day yesterday, and other things got in the way of motorcycles, so the bearings and bosses haven't been measured yet to check ovality, taper or fit. Hopefully later today...

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Well, that "later today" took somewhat longer than planned, with that silly"paid work" nonsense getting in the way, along with 40 days and 40 nights of rain.

Things have been progressing in the background, but not really enough to warrant [lack of] progress posts. Most of the tools to make the tools to work on the bike have now been bought or made or fixed, so perhaps some posts with pictures this coming week.

The flywheels are pinched in opposite the crankpin, so well outside the 0.002" runout specified in the BSA Service sheet. This afternoon's exercise was to try to spread them to bring the mainshaft runout into spec.

We tried using the hydraulic press and a wedge, with Al angle to protect the crank cheeks. Measuring the outside faces of the flywheels with a set of digital calipers as we went to find when we got within the ballpark. It seemed to be making some progress, but the flywheels sprung back into their previous place once the pressure was released.

The Service Sheet says to align to within 0.005" before tightening the crankpin nuts, then to align to within 0.002" after tightening. This tends to show that the alignment should be able to be improved with the nuts tight, but no luck today.

This is my first built-up crankshaft alignment, so it's rather fumbling in the dark.

Should we loosen the crankpin nuts and try to bring within spec?
Is the time-honoured Mjolnir approach better than using a new-fangled hydraulic press?
When using a press, should I overshoot by a long way and hope it springs back close to the right dimension?
Is there a preferred size and material for the wedge?

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I’m not really qualified to comment on the subject, but have been down this land mine laced road before. Wedge material is whatever you can find. Aluminum, brass, iron wood. Usually the Mjolnir approach is better. The shock will encourage things to move.
If there is crap between the shoulder of the pin and mating surface on the flywheel or the surface is damaged, then you’re flogging a dead horse. Normally when assembling a crank, I would make that adjustment before the nuts are torqued (but relatively snug). Not saying that’s the correct way…just how I would do it. Once flywheels are parallel and aligned within the ballpark, then torque them. Followed by the bashing required to get them within the .002”.

Hopefully things will go smoothly.

Last edited by Cyborg; 08/14/22 2:56 pm.
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Originally Posted by Shane in Oz
Should we loosen the crankpin nuts and try to bring within spec?
When using a press, should I overshoot by a long way and hope it springs back close to the right dimension?
If the three pieces making up the crankshaft are rigidly clamped together, the only way overshooting would work is if you were able to bend the metal, rather than shifting it at the locations where they're clamped.

I can't think of anything you have to lose by loosening the nuts, which is what I would do if I were in your position. That is, loosen the nuts and try wedging them apart again. If that works, tighten the nuts, determine if the situation has improved, and use that to determine how much to overshoot on the next attempt after loosening the nuts again. If it all goes south, let me know so I can delete this post and deny that I ever wrote such advice.

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Originally Posted by Magnetoman
I can't think of anything you have to lose by loosening the nuts, which is what I would do if I were in your position.
That's what I thought would be the case. Unfortunately, they seem to have been tightened by Bruce Banner in a bad mood.
Oh well, time for some heat and the Ingersoll Rand air impact gun frown

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Originally Posted by Shane in Oz
Unfortunately, they seem to have been tightened by Bruce Banner in a bad mood.
It's for times like this that I have a 700 ft.lb. impact driver.

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Originally Posted by Magnetoman
Originally Posted by Shane in Oz
Unfortunately, they seem to have been tightened by Bruce Banner in a bad mood.
It's for times like this that I have a 700 ft.lb. impact driver.
According to the blurb, my 2135QTiMax should be 550 ft.lbs forward and 780 ft.lbs reverse, so fingers crossed. It was bought for working on International Harvesters and John Deeres, which tend to be somewhat larger than BSAs.

The fall back is to fire up the Broom-Wade mobile compressor and use the 1" drive impact wrench.

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Originally Posted by Cyborg
Wedge material is whatever you can find. Aluminum, brass, iron wood.
I wan't sure about using an iron wedge, hence the angle Al to protect the flywheel cheeks.

Originally Posted by Cyborg
If there is crap between the shoulder of the pin and mating surface on the flywheel or the surface is damaged, then you’re flogging a dead horse.
La la la la la - I can't hear you.

Originally Posted by Cyborg
Normally when assembling a crank, I would make that adjustment before the nuts are torqued (but relatively snug). Not saying that’s the correct way…just how I would do it. Once flywheels are parallel and aligned within the ballpark, then torque them. Followed by the bashing required to get them within the .002”.
That's what Magnetoman said as well, and does seem to be the next step.

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Originally Posted by Cyborg
......I would make that adjustment before the nuts are torqued (but relatively snug)........... Followed by the bashing required to get them within the .002”.........
I've trued quite a few built up BSA cranks and a few Harleys and even an Indian. This is what works for me.

First tighten the nuts about quarter tight, around 40-50 ft/lbs on a B50 or a Gold Star. Check the rim outside diameter faces 90 degrees from the pin with a straight edge and use a brass or lead hammer to move them into alignment while resting one flywheel on a block of wood. (I like it to be on the floor.) Then micrometer measure the width at the pin and compare to the width 180 deg around. Correct this by clamping in the vice or spreading with a BIG chisel/wedge and a hammer until the measurements are within a thou or two.. It should move relatively easily at this stage of roughing things in.

Any movement to get it closer to where you want it will also tend to seat the tapers so you will need to tighten things up again and depending on progress, maybe 1/2 tight.... Fully expect this to change the alignment!

Repeat the first two paragraphs as needed until about 3/4 - 7/8 tight but with additional measuring of crankshaft width at the pin and every 90 deg around.

Once the crank is nearly fully tight and you are chasing that last couple of thou or even a half thou or so of shaft runout with a dial indicator on rollers or centers, adjustment will become difficult, but that is what you want. Any change will take some real force. Cyborg's instincts about impact force are dead on. If they weren't hard to move when fully tight, the crank could be knocked out of true just from running.

Once you are satisfied that the crank is true enough, give it a final torquing to full spec. (Hoping it doesn't change on you.)

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Originally Posted by Shane in Oz
....... should I overshoot by a long way and hope it springs back close to the right dimension?
Is there a preferred size and material for the wedge?
"by a long way" is a bit subjective but the idea is right. Your local judgement governs. Overshooting with resulting springback to hopefully truer running is exactly what I would do.

I use a big ugly chisel for a wedge and sometimes use spacer metal if the chisel isn't wide enough. But, you may need to hit it pretty hard and extra spacer pieces sometimes won't stay put while you are hammering in your wedge.

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The crank for the current project moved when torquing, but it’s fixed now.

Hopefully when it come time for you to get within the final .002”, it will take quite a bit of force. Not the dainty little “tink” shown at 27:32




My buggered rotator wouldn’t allow be to beat the Comet flywheels against a stump, so I used an ingot of Pb and a sledgehammer. I’d describe the process, but you folks might think I’m slightly insane… got it under .002” though.

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Originally Posted by Cyborg
.....My buggered rotator wouldn’t allow be to beat the Comet flywheels against a stump, so I used an ingot of Pb and a sledgehammer. I’d describe the process, but you folks might think I’m slightly insane… got it under .002” though.
Those of us that have been down that road understand. It takes calculated brute force applied with a deft touch to get there.

Having said that, I did meet my match when someone brought me a Ducati L twin crank that had been pressed together with a slight twist across the crankpin. It simply would not move though I tried mightily until the head of my 5 lb sledge fell off. True story!

And heck, a little insanity keeps things interesting.

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This is not meant to gloat, but Shane's travails come just as I'm about to emphasize in my thread on tooling the usefulness of being able to fabricate special jigs. The jig shown in the photograph ensures the shafts are very nearly coaxial and the flywheels parallel before even starting to tweak them into final alignment

[Linked Image]

Knowing this doesn't help Shane in the least, but it does help me make that point. So, thanks Shane...

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What sort of oil passageway enters the crank pin on a BSA 350? Do you have to align the pin to the oil passageway or is there a passageway around the inner circumference of the pin that negates the need for alignment?

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Originally Posted by Magnetoman
the usefulness of being able to fabricate special jigs. The jig shown in the photograph ensures the shafts are very nearly coaxial and the flywheels parallel before even starting to tweak them into final alignment

[Linked Image].
Making one of this will probably be on the cards if the crankshaft has to come apart. I do have the materials, but so far have avoided actually doing anything with them.

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Originally Posted by Magnetoman
Originally Posted by Shane in Oz
Unfortunately, they seem to have been tightened by Bruce Banner in a bad mood.
It's for times like this that I have a 700 ft.lb. impact driver.

But the burning question is how was the 700ftlbs measured as apparently there is no standard for measuring the torque of impact wrenched.
I bought the biggest gun I could find that would run on a 1/2" air line & run mine at 100 PSI.
This was needed for removing blade bolts that had self tightened during use to the point that 1/16" thick cup washers were clamped flat
IT is supposed to be 1400 ft lbs reverse torque and while it seems to be a bit stronger than Shanes, it is not that much stronger .
However after near 10 years of very very heavy use I fear that it has lost a substantial amount of torque
However Shane's crank pin nut just laughed at it , so I can see a day sorting the BoomWade out in the near future .


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I had an alternator rotor nut on a B50 motor that laughed at my impact wrench (a cheap one from HF). A friend who sells tools came over with a new impact wrench. I don't remember the brand or what it was rated at, but it was something substantial. The nut laughed at that too. We tried heat, penetrating oil, nothing worked. Eventually, I had to cut it off with careful Dremel and cold chisel work. It was still stuck to the crank end with a third of it removed! Finally got it off. Turned out that the nut was the right tpi, but the wrong thread angle. The previous owner, was presumably able to get it started and then tightened it with an impact wrench. I was able to clean up the threads and save the crank. I am not suggesting that you have the same situation, but at this point, it looks like the crank has to come apart, and you should probably replace that nut, so consider cutting it off.

Ed from NJ

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Originally Posted by Shane in Oz
Originally Posted by Magnetoman
the usefulness of being able to fabricate special jigs. The jig shown in the photograph ensures the shafts are very nearly coaxial and the flywheels parallel before even starting to tweak them into final alignment

[Linked Image].
Making one of this will probably be on the cards if the crankshaft has to come apart. I do have the materials, but so far have avoided actually doing anything with them.


It is possible to kick that can down the road. Although it takes more farting around, you can use a mill. For accuracy I used a dedicated Japanese 4 jaw for holding the drive side to the bed. Timing side is held in the quill with a collet. The timing side can be coaxed onto the pin far enough that things will stay put while you transfer it to the press. I have a ball joint installer to help with the coaxing. Not as ideal as MM’s jig, but works.
If I’m ever tempted to engage in any further self flagellation, one of the locals offered to lend me his jigs, so I’ll go that route.

[Linked Image from live.staticflickr.com]014C70F0-194A-4C99-B21F-52DFF192FB63 by First Last, on Flickr


The reason I inquired about the oil passageway. It might tip the scale when deciding if you want to go all in. This is from a lesser marque.

[Linked Image from live.staticflickr.com]741595C2-611C-4902-99A6-EA3B967986A8 by First Last, on Flickr

[Linked Image from live.staticflickr.com]0B65123D-0738-4B92-91B5-08CA7ECB9D15 by First Last, on Flickr

[Linked Image from live.staticflickr.com]D1A9C470-27E0-431D-BA53-3CBF5AFAA457 by First Last, on Flickr

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Originally Posted by Cyborg
Although it takes more farting around, you can use a mill.
That's an interesting technique that I'll try to remember since it could be applicable to other situations as well.

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