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T140 TS Bearing
#800685 03/10/20 8:52 pm
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Dr. Z Offline OP
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All of my past experience is with the TS bush on the T100 and BSAs, and now I am reassembling the engine on the 76 T140 with the ball bearing. The TS bearing appears to be a press fit onto the crankshaft, and I do not want to use a hammer or use too much heat on the inner race. Is there a simple way to get the cases back together without putting too much stress on the bearing? I do not know if a previous owner might have replaced this bearing.


Craig Zaspel

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Re: T140 TS Bearing
Dr. Z #800726 03/11/20 8:03 am
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Originally Posted by Dr. Z
All of my past experience is with the TS bush on the T100 and BSAs, and now I am reassembling the engine on the 76 T140 with the ball bearing. The TS bearing appears to be a press fit onto the crankshaft, and I do not want to use a hammer or use too much heat on the inner race. Is there a simple way to get the cases back together without putting too much stress on the bearing? I do not know if a previous owner might have replaced this bearing.
Hi Craig, I agree, no hammer or heat. This bearing is supposed to be a sliding fit on the shaft. It's held in place by a clamping washer behind the half time pinion and the nut. I saw a video with John Hudson of Nortons, who "eased" the shaft with emery cloth. This may seem a bit low-tech but chances are that your shaft has a slight high-spot somewhere that needs to be dressed down.
The bearing must be fitted to the case first, after which you fit the crank, but you knew that I'm sure.

Hth
SR

Re: T140 TS Bearing
Stein Roger #800795 03/11/20 9:30 pm
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Dr. Z Offline OP
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Thanks SR, some work with emery cloth made it a sliding fit.


Craig Zaspel

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Re: T140 TS Bearing
Dr. Z #800803 03/11/20 10:33 pm
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Quote
Thanks SR, some work with emery cloth made it a sliding fit.

No, the interference fit on the crankshaft (and the crankcase) is calculated for the timing side ball bearing to have the correct running clearance. When a bearing is an interference fit the pre-fit running clearance will close up when installed. This will be up to 75% of the interference fit with the contraction of the outer race and expansion of the inner race. Balls like to have very little running clearance. For this ball the cold running clearance typically approaches nil.

Of course sanding the shaft must be correct, I saw it in a video! Would it be rude to say the next time try a engineering bearing manual.

Re: T140 TS Bearing
John Healy #800809 03/11/20 11:00 pm
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Dr. Z Offline OP
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John, It would not be rude. I have been considering converting to a 76 degree crank, so maybe now would be a good time.


Craig Zaspel

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Re: T140 TS Bearing
Dr. Z #800852 03/12/20 8:17 am
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Originally Posted by John Healy
Quote
Thanks SR, some work with emery cloth made it a sliding fit.

No, the interference fit on the crankshaft (and the crankcase) is calculated for the timing side ball bearing to have the correct running clearance. When a bearing is an interference fit the pre-fit running clearance will close up when installed. This will be up to 75% of the interference fit with the contraction of the outer race and expansion of the inner race. Balls like to have very little running clearance. For this ball the cold running clearance typically approaches nil.

Of course sanding the shaft must be correct, I saw it in a video! Would it be rude to say the next time try a engineering bearing manual.
I related what John Hudson did, but I know you're correct and he and I are not. However I must confess that my mechanical vocabulary in English isn't great, and sliding fit would be the wrong term.
Interference fit it is, but in any case, Craig didn't want to use a bigger hammer and I agree. The inferred suggestion was to "ease" any high spot, which is what I would have done.
I have to ask, how would you have approached this?

SR

Re: T140 TS Bearing
Dr. Z #800853 03/12/20 8:29 am
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Warm the bearing in oil?

Re: T140 TS Bearing
Dr. Z #800906 03/12/20 6:51 pm
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Further to JohnH's comments, the fit of the bearing ID on the journal OD is important for more than one reason.

On earlier cranks, the journal to bearing fit was quite a serious interference, such that when parting crankcases the bearings would often remain on the journals.

I believe, from what I've read on this site, that later cranks have a slightly reduced interference fit (ie the journals are ground a few tenths of thou smaller) and this resulted in a bearing specification change for the 750 from the 650, due to the bearing internal clearance change resulting from this.

Of course it would be much more convenient if main bearing inners were a slip fit on the crank journal (it is hard work to get the drive side inner roller off, and not much easier on the timing side, so I fully understand the temptation to ease the journal for a slip fit.

In some ways it is similar to easing the fit between cam pinions and camshafts for ease of removal/fitting. But it is not the same. This situation doesn't have enormous forces exerted upon it.

The fit between crank journal and bearing ID must be less than zero to guarantee that it is zero. If the bearing slides on to the journal, there is clearance. It may only be a tenth of a thou (I doubt you'd get to that uniform precision with emery cloth). That clearance will allow the journal to wander within the bearing ID, no matter how tightly it is clamped by the end nuts. That will eventually slacken the clamping to allow the journal to spin within the bearing ID, causing wear to the journal. How else would one imagine the journal wearing on cranks, when the bearing ID is supposedly clamped by nuts?

Re: T140 TS Bearing
Dr. Z #800917 03/12/20 7:54 pm
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Point taken, and of course you are all correct.
But I live in the real world fixing all kinds of worn out machinery and I, or the guys that bring their old bikes to me, can't or won't afford to change crankcases or crankshafts or both to obtain the perfect fit and preload every time, and this is reflected in my methods I suppose. Most shafts will have a "tap-on fit", some will be tight due to abuse of some kind, some will be loose. Hell, I've even been seen to use Loctite bearing retainer. If tight, yes I do "ease" the shaft slightly.
Still I, and others, have run these engines for extended mileages, and I've never had one with main bearing issues.

But to get back to the Original Post for a second, should I have said "just hammer it in Craig"?
I should have said interference fit though, too late now.

SR

Re: T140 TS Bearing
Dr. Z #800926 03/12/20 9:03 pm
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Hi SR,
I realise we live in a less than perfect world, and often we have to make compromises to get a working bike from the bits available.

Just maybe if the bearing seemed too tight on the journal it would be better to see if there was a tight spot (through clumsy bruising perhaps) by partly fitting the bearing and seeing where the shiny bit was. That could then be eased without reducing the whole journal.

The OP's experience of tightness may just have been a usual interference fit for all we know.
I've always had to at least gently tap bearing inners onto the journals, mostly rather more firmly with older cranks.

I don't for a minute think that what has been done has ruined the crank, just less than ideal in the long term.
Frettus Nottus Dave

Re: T140 TS Bearing
Dr. Z #800938 03/12/20 10:00 pm
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With the t140 and t120v you are better off fitting the NUP type 3 piece roller on the timing side anyway.
Makes life easier and is only a couple of bucks more.

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Re: T140 TS Bearing
Dr. Z #800941 03/12/20 10:12 pm
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Agreed. The inner race still needs to fit on the journal though.

Re: T140 TS Bearing
Dr. Z #800953 03/12/20 11:46 pm
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However---there are interference fits and there are interference fits.
Why?--because of that aspect which we often ignore but is always floating around---tolerances.
Even a bearing inner bore has a tolerance and the crankshaft certainly does.
Tolerances can make a light interference fit a heavy interference fit.
I would not use a heavy interference fit in this application for fear of shortening the life of the bearing.
Instead I would carefully linish the shaft using worn out fine emery paper with a drop of light oil.
Slowly and carefully and checking the fit as you go until the bearing will go onto the shaft with light tapping from a Birmingham screwdriver.
Just my two cents worth of course.

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Re: T140 TS Bearing
Dr. Z #800980 03/13/20 2:51 am
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Interesting discussion. Before the emery cloth I tried tapping (light taps of course) on a socket over the inner race with an engineer's hammer. Nothing happened and I was afraid to give it a smart rap with the hammer, so that was where the original post started. At this point of the project I will use the crank as is and see what happens, with the long term goal of a 76 degree crank. I enjoy working on these old machines and I originally got the T140 to have as a project if I ever retire.


Craig Zaspel

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Re: T140 TS Bearing
Dr. Z #801040 03/13/20 2:05 pm
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Yes, there are times when you have to accept what you have.

But to set out, and take a perfectly good crankshaft, and render it to a less than perfect condition, doesn't appear to me as good stewardship.

One of the main considerations when selecting the pre-fit running clearance reflects one of three conditions:
• The bearing is a slip fit on both the inner and outer races.
• The bearing is a interference fit on just one of inner or outer races.
• The bearing is an interference fit on both the inner and outer races.
There are others such as the amount used for the press fits, load etc..

The bearing in question in this application has a pre-fit clearance of C3 which is more than normal (CN). Just seeing a bearing specified as C3 condition is a very good indication that it as selected to be a press fit on both the inner and outer race.

A ball with CN rating (less than normal) would be used when only one of the races is an interference fit.

Now Tridentman brings up a point that he will see begs the point of his observations. In fact it is about his favorite bikes, the Tridents. What appears on the face of it to be the same bearing is used on the drive side of the Triples. In fact it uses the same part number - 70-1591 (RHP MJ1 1/8). Now having a bearing in two conditions with the same part number seems like it would cause confusion. Along with a whole bunch of parts that are different, and share teh same part number, bearings didn't escape this folly. They did it to the drive side roller (70-2879) which has two iterations: CN and C2.

There is one thing that is different from the twin. On the triple It is a slip fit on the crankshaft. There is a difference in the bearing specification between the two. The triples use a CN with its less pre-fit internal clearance and the twin uses a C3. Both sharing the 70-1591.

There is a know condition in Triumph 650 and 750 twins that happens to the drive side roller bearing especially when the bike is used with the alternator rotor nut loose. The crankshaft wears leaving the inner race a slip fit on the crankshaft. The interference fit on the drive side bearing inner race is greater than on the timing side. Again the pre-fit clearance relies on this interference fit to attain the desired running clearance.

Unlike balls that like a near nil fitted running clearance (diametric clearance), it is essential that the roller in these applications has running clearance typically in the 0.001 inch range. Failing achieving that, the bearing can be noisy, allow for vibration or fail. We have been recommending engines, where the inner race has lost its fit on teh crankshaft, to use the roller in a C2 condition (also used in the 1976-up models manufactured after the worker's co-operative took over manufacture and distribution.

One should note that the pre-fit internal clearance for a normal (CN condition), is greater for a roller than a ball. It needs to be for the bearing to be able to reach their desired diametrical clearance when fit.
Just thinking

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Re: T140 TS Bearing
Dr. Z #801043 03/13/20 3:01 pm
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Actually, John, my observations related to the twins (I agree with you completely on the triples).
I accept that you need an interference fit between the inner bore of the bearing and the crankshaft.
But tolerances-- particularly on the crankshaft diameter may give a light interference fit on some crankshafts and a really heavy interference fit on other, nominally identical, crankshafts.
In the latter case I consider it sensible to linish the crankshaft to give a light interference fit so that the bearing can be tapped onto the crankshaft rather than needing to be heavily hammered on.
IMHO this is particularly so if you might need to fit and remove more than once in order to set crankshaft end float.
Just my two cents worth of course.

Re: T140 TS Bearing
Dr. Z #801062 03/13/20 5:59 pm
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I'm stuck between both problems, on my 66 TR6 someone has been kind enough too knurl the main bearing surfaces. This meant the bearings were a heavy press fit. This time around I have lightly dressed the high spots until I could get the bearings to just start when I rock and press them on by hand. They are still by no means a sliding fit.

Rod


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Re: T140 TS Bearing
Dr. Z #801072 03/13/20 6:37 pm
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Heating the bearing is the recommended way to do this job, but the induction heater to do this job is not a part of most motorcycle shop's tool kit. But after heating the crankcase to 212°F (the entire case, not just locally around the bearing housing), and offering the bearing to the crankcase, the case itself acts like an induction heater. The bearing will soon heat up to the recommended temp. of 150° F to allow the crankshaft to slip into the inner race. I have been doing it this way for years. It would be the rare exception that this didn't work.

Removing the crankshaft is a different story.

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Re: T140 TS Bearing
John Healy #801074 03/13/20 6:47 pm
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Originally Posted by John Healy
Heating the bearing is the recommended way to do this job, but the induction heater to do this job is not a part of most motorcycle shop's tool kit. But after heating the crankcase to 212°F (the entire case, not just locally around the bearing housing), and offering the bearing to the crankcase, the case itself acts like an induction heater. The bearing will soon heat up to the recommended temp. of 150° F to allow the crankshaft to slip into the inner race. I have been doing it this way for years. It would be the rare exception that this didn't work.

Removing the crankshaft is a different story.


Heat hammer to 150*F? Sorry John and please nobody do this. Mark

Re: T140 TS Bearing
Dr. Z #801077 03/13/20 7:03 pm
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Where do you see "Heat hammer"?


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: T140 TS Bearing
Dr. Z #801090 03/13/20 7:50 pm
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I've "liked" a couple of the above posts, they provide information that I either didn't have, or that I needed reminding of.
There's no doubt I'm a novice in many respects to people with real knowledge, but I regularly arrive at passable results anyway. Dumb luck maybe?
I do hold John Hudson in high regard though, even if he took an emery cloth to a main shaft. For those who don't know, he was a famous Mr.Fixit service manager with Norton.
Some would call it a Hillbilly approach to engineering, but as I live with my toes in the North Sea, I prefer the term Fishermans Way.
When you had a single engine to get you back to the shore, you got creative real fast if it failed on you!

SR

Re: T140 TS Bearing
Dr. Z #801120 03/13/20 9:52 pm
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I have done things at the race track that I would never have done at the shop.

Like the time I straightened a pretty bent push rod on the cement floor with a hammer. A guy who watched me do it came up to me after Jerry Wood had taken the bike and won the race. He said he wouldn't have believed me if I told him that unless he actually saw Jerry win.

To paraphrase Koan, "Some times you have to do what you have to do!"

Re: T140 TS Bearing
Dr. Z #801129 03/13/20 10:42 pm
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i confess that i have also done some things at the races. i have gone down the track at 130 mph with my fuel tanks held onto the frame with duct tape and the motor mount bolts held in place with safety wire because the CEI nuts had vibrated off and my wife hadn't got back with replacement SAE bolts.

oops


every day you do not take a chance is a day of your life that you will never get back.
Re: T140 TS Bearing
Dr. Z #801141 03/14/20 12:06 am
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When I lived in UK there used to be a guy who rode an old Norton single who turned up at every rally and swap meet in the Midlands.
The barrel had split just above the flange holding it to the crankcase.
He kept it together by driving a wooden wedge between the top of the rocker box and the top frame tube.
Ran it like that for several years at least.
Surprising how much abuse these old Brit bikes will take and still keep running!

Re: T140 TS Bearing
Dr. Z #801145 03/14/20 12:36 am
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Tridentman,
The greatest story ever told and I bet there are thousands just like it. After a pit stop in the middle of nowhere I fired up the 68 and the wiring harness behind the headlight went up in a cloud of smoke. Fortunately the copper did not melt but the insulation was all gone. I carefully separated the crispy wires and took off my leather gloves. I placed the fingers of the gloves between each of the wires and anything they might short on. Bike fired up on the first kick and I drove the 50 or so miles home. My buddies on their Jap bikes are still shaking their heads. And there are people out there who gnash their hands and wring there teeth about every nut and bolt on these old turds.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
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