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Hi all -

Trial fitting gearbox cover to check indexing, fit, etc. Having trouble with the gearbox end of mainshaft and the bearing in inner cover. Clearance is really tight. Can’t even get the old bearing to go on the mainshaft. Tried a bit of heat on the inner race of the bearing, but no love.

Is there an elegant solution to this? Clearly don’t want to break out a dead blow hammer here…

TIA,

Steve


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Hi Steve, I have 2 main shafts. The one in the bike & a spare. Both fit original bearing & new bearing the same. Snug slip fit.
Had to bump heal of hand on cover or other shaft end to slide bearing over shaft. But not very hard.

How does it fit into the old bearing?

My hunch is the ID of the new bearing is on the small side of tolerance. It could be shaft is on larger side of tolerance as well.

If warming bearing doesn’t expand it enough the fit must be pretty tight.

Did you get bearing from Triumuph parts vender?

I got my recent bearing from Bonneville Shop & it fit good both to inner cover & the shaft.

I’ve run into steering head bearing that fits so tight on stem it’s basically impossible to adjust accurately. Oriellys Auto parts sells a very small 2 arm brake hone. I’ve used this to hone ID of steering head bearing to just snug sliding fit. It might go small enough to hone ID of main shaft bearing?

If you have micrometer can you measure shaft diameter? Verify it reads zero first. Calibrate is needed. Measure shaft. Estimate the ten thousandths best you can & take photo of reading very straight on.

If you have high quality vernier caliper measure I’d of new & old bearings.

Ado measure shaft for taper from end to where bearing rides.

That should show where problems are.
Don


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Thanks Don -

I'll take some measurements tomorrow when the temps have stabilized out there. I've had the heat on out there today, so there's hot/cold spots in the garage.

I got the bearing from CBS, Japan manufacture. Surprisingly I can't seem to get the old (original) bearing to fit/slide on the shaft either? The cover came off with little trouble. No damage to end of shaft/splines that I can see....

Steve

Last edited by JubeePrince; 01/08/22 3:01 pm.

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Is it a new mainshaft? Some of the mainshafts supplied by LF Harriss aren't quite right - I had one that was 5mm longer than standard at the clutch end, and I also had a mainshaft 3rd gear I didn't like the look of (teeth machined strangely, with 'fish scale' markings on the flanks of the teeth - I didn't use it)


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Original/same mainshaft.

Replaced high gear, layshaft and three bearings.

Steve


'77 T140J Silver Jubilee
'82 T140LE TMA Royal
‘69 BSA Rocket 3 (patiently awaiting it's turn)
"Vintage Bike". What's in your garage?

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Mainshaft measured across three sets of splines. Consistent with mic.


Mainshaft = .7495"

ID of old bearing = .7460"

ID of new bearing = .7465"

.003" difference assuming I measured correctly.

Perhaps try a bit more heat on the bearing race? Hone/sand the ID on bearing?

TIA,

Steve

IMG_3227.jpeg
Mr. Blutarsky... 0.0

IMG_3229.jpeg
Spline Measurement

IMG_3229.jpeg
Mic scale

IMG_3230.jpeg
New bearing measurement


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My cheapo digital vernier reads 0.020 wrong on internal, best check yours against a standard

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Yeah, just finished doing that. Hard to get accurate reading with caliper while bearing is in situ. I did check my caliper with a standard.

Using bore gauge and micrometer, I came up with the following:

ID of old bearing; .7500" Was able to get a slip-fit with a bit of heat on it.

ID of new bearing: .744" no bueno even with some heat.

Clearly the ID of the new bearing is too small for the shaft.

Need to come up with a way to relieve the ID or try a different bearing..... I did send an email to CBS to see if they've experienced this issue before.

Steve

IMG_3232.jpeg
ID of old bearing

IMG_3231.jpeg
ID of new bearing

Last edited by JubeePrince; 01/08/22 6:48 pm.

'77 T140J Silver Jubilee
'82 T140LE TMA Royal
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The boy done good, as we say!

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...if you use RHP or NSK for that bearing would be no problem at all. NSK normally have the shield; remove it and just that. NSK in that measure are everywhere. About 12 Dollars here.
Very strange because that is the easiest and cheapest bearing for the engine.

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Hi Steve, You can plainly see the shaft diameter is .7505”. You can fairly closely estimate the ten thousandths even without the lines. Especially the 1/2 as our eyes are good at finding a mid point.

Indeed it is very hard to measure bore without specific bore measuring equipment. Snap gauges are very useful but not accurate enough to split the 10 thousandths. I’ve been down the measuring bearing bore road many times. I’ve given up to get accurate ID, but comparing 2 bearings you can see difference if there is any. I’ll measure both several times & average readings.

For a sliding fit the bearing will measure nearly the same as shaft. Shaft & hole exactly the same is already light press fit.

Your micrometer stand is very handy isn’t it!! When we’re splitting hairs even the heat of your fingers matters.

I don’t really know what brand bearing is closest to spec. Or most durable.

Splines generally don’t burr up on hardened shafts, but it must be checked.

I’m kind of busy today. I’ll check my parts tonight if possible.
Don


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This is why I stock RHP bearings! And try to be careful ( I am not perfect) when I buy other brands. Several Japanese companies source their bearings out of China (or bearing parts and assemble them in Japan (read: Made in Japan)).

While the country of origin marking is a big thing here in the US, it isn't in the rest of the world. Taiwan is very good about direct imports into the US with their Made in Taiwan marking.

It can be a different story with parts from the UK. Many brand name companies buy products in bulk from the far-east, then claim made in UK status because the cost of individually boxing it in the UK (technically wink-wink) allows them to mark it made in UK! Some just don't put any country of origin on the box/parts at all.

The current lot of Harris 57-7077 mainshafts (made in Taiwan) measure 0.749" while the stock ones I have laying around measure 0.7495".

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I'm in an email conversation with CBS now. We'll see what their solution is.

So, John, what vendor of yours stocks the RHP's?

Cheers,

Steve


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'82 T140LE TMA Royal
‘69 BSA Rocket 3 (patiently awaiting it's turn)
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Originally Posted by TR7RVMan
Hi Steve, You can plainly see the shaft diameter is .7505”.

How are you arriving at the figure Don?

I get .725 from the sleeve and .024 plus .0005 from the thimble

The zero on the thimble is just SHY of the line on the sleeve, not just past it.

Total = .7495

But maybe I'm missing something? Wouldn't be the first time.....

Steve


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[Edited double post]

Emailed with CBS. They requested bearing to be ret'd, they want to measure it themselves. Sending it out tomorrow. They claim to have been selling this bearing for six years without any issues, so it'll be interesting to see what they find.

I measured the ID of bearing again after removal from cover: ~.7440".

It's stamped Japan WTW RLS 6

Cheers,

Steve

IMG_3238.jpg
New bearing

Last edited by JubeePrince; 01/09/22 2:50 pm. Reason: double post

'77 T140J Silver Jubilee
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Hi Steve, That is correct the way you are reading mic. With barrel, then thimble & estimating between lines on thimble.

Just got back from garage.
My spare used mainshaft is genuine Triumuph. Diameter
.7495”.

Using snap gauge my old used bearing measures .7493”. Should be press fit…. However is easy sliding fit. So obviously the snap isn’t accurate.

Looking at old shaft you can se bearing was rotating on shaft. Looking at my old bearing it was rotating on shaft & the ratchet not was a little loose with tab washer keeping nut from backing off more. 9 out of 10 I find loose. I always Loctite that nut & bend both tabs.

The bearing from Bonnie Shop was JAF made in Japan. Never hear of them before.

Your shaft measures .7495”. The bearing will be decided press fit I’d think.

I looked at my notes. I measured shaft but didn’t record diameter. As I said before it went together as expected without undo force of any kind.
Don


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Originally Posted by TR7RVMan
H
My spare used mainshaft is genuine Triumuph. Diameter
.7495”.

Thanks, Don. Spoke to PO who owned the bike from new, original mainshaft. So I'm satisfied with my result of .7495'

Cheers,

Steve


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...it s cheaper to buy an NSK and just that. May be you want to know the "why´s"

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So the plot thickens. CBS got my Japanese bearing back and they say the ID measures out to .750". Accordingly, bearing is not defective. I've asked them to send it back to me.

I'll be the first to admit, I'm not a machinist, but I got a range 0f .7944" - .7965" depending on the tool (cheap digital caliper, micrometer w/standard and bore gauge). The kicker is those same tools measured out my mainshaft at .7495" (within spec) and there are no issues with the splines (checked with magnifying glass), gear cluster went back together easily.

So if the bearing is to spec then it would stand to reason that the mainshaft is out of spec. However, this bike comes from an owned-since-new PO. I trust him when he tells me that the mainshaft is original to the bike. But anything is possible.

I think my plan at this point is to verify the ID of my bearing independently when I get it back. If I can verify that, then I can isolate the problem to the mainshaft or the bearing.

To be contiunued....

Steve


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ID's are a lot harder to measure than OD's. The mainshaft may be .7495" but it may be marred at the chamfer that enters the bearing first stopping it from going on. A past pressing on of a bearing at an angle can leave a shaft like that.

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But the original bearing came off OK?

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Tom Gunn, a laison between the US distributor in Baltimore (reporting to Rod Coates), and the engineering group at Umberslade Hall did a study of all the brand of bearings BSA and Triumph were using in production. I went on for several pages of bearings and their tolerances. To make this short they were all over the place. Different brands would require changes to tolerances when the mating parts were machined. BSA did the buying and their prime concern, as they were going broke, was cost, not precision. The point of the exercise was there was a cost when changes had to be made in machining the mating parts.

We also sell JAF Japanese bearings for this application. Measuring the ones we have in stock and fitting them to factory and Harris mainshafts, I find them snug when offering them to most factory shafts measureing 0.7495" and a slip fit on the Harris shafts measuring 0.749".

The RHP fit both shafts.

It is normal to have a shaft measure on the high tolerance and a bearing measuring on the low tolerance and have the bearing a tight on the shaft. In these cases production would grade the shafts and bearings to be sure they would not have problems on the assembly line.

This was normal for pistons and cylinders. The were graded and marked before they reached assembly. They were not making Formula one engines. Far from it!

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Original came off OK. Slight rap on the cover “ear” from the primary side with a piece of hardwood to break the sealant used. It pulled of with a bit of effort, rocking cover back and forth, but I can’t get the old bearing back on the shaft without heating it first and with the mainshaft at about 40-50F when my garage heat is off. This is ideal as the bearing won’t spin on the shaft, but I could barely get the new bearing started on the cold shaft with some heat on the inner race. I know the shaft is hardened, but I was afraid of tearing the start of the splines.

I was hoping to “rock” the cover and new bearing back on the shaft, but it was not “snug”, it was “tight”.

CBS is advising that I use a dremel to relieve the lip/edge of the race to get the bearing started. I will try to bake the bearing and cover to 325F to install on the cold shaft.

John, thanks for the additional info. These old bikes can be fiddly. I’m just writing and asking questions and guidance here so I don’t damage anything!

I have also ordered an RHP bearing, so I hope to be able to get one or the other installed.

Kommando: true. Examined both mainshaft and bearing with magnifying glass. Didn’t see anything that would cause the bearing to bind.

Cheers,

Steve, who is becoming an amateur machinist out of necessity.


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Hi Steve,
“Original came off OK. Slight rap on the cover “ear” from the primary side with a piece of hardwood to break the sealant used. It pulled of with a bit of effort, rocking cover back and forth, but I can’t get the old bearing back on the shaft”

This must be a clue surely? It makes me think that the final bit of removal action somehow left a tiny raised edge on the shaft. This may be so tiny as not to be visible under small magnification (less than half a thou could make a difference).

I’d try just slight easing of the leading edge of the shaft journal. The journal is not nearly as hard as the bearing inner.

As the old bearing came off without too much difficulty, but won’t go back on, I would view as crucial info. Trying other bearings rhymes with red-herrings.

Just thoughts Dave.

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Kyle here - sounds like your mainshaft was / has been skidding in your bearing

I measured your new bearing from me using a gauge (caliper) and it was .750"

So, I measured using a bore gauge (.0001") and a micrometer as the gauge

Each bearing has an ID of .7493"

That is .0007" smaller than 3/4" (.750)

See photos

Also, bearings do have tolerances

Someone stated that the Triumph maninshaft is .7495", well, with my bearing you have an interference of .0002"

Sounds good to me..


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