Crank movement

Time Warp said:
1/8" sounds kind of high. (I machined the top off an original AE to see inside but forget the actual clearance piston bosses to rod)
I had 0.31" on one crank, 0.029 on the replacement. (but machined stainless shims anyway since I was there to reduce it to around 0.012")
It probably made little difference in my case and if I could not have made shims would not have bothered.

View attachment 80132 View attachment 80131

About the only thing I did not care for was the massive step from the stator to rotor so I moved both of them inboard and to inline, it looks much better and might have gained 0.2 of a volt output as a bonus.
Click to expand...
Looking at your pictures, I see outer race shims involved in your shimming procedure. On my present project I have to reduce the end float by about the same figures as yours. After inspection, both my Superblends have a very slight slide in the cases (no heat needed to drop the ice/cold bearings in the cases).
1: Despite outer race shimming a lot easier than the traditional inner race method, would you scare that possible bearing spinning could destroy the shims and debris come in contact with the rollers and destroy the bearing itself?
2 : Would you just put some Loctite in the cases to prevent spinning and if so, what about the bearing extraction if needed in the future?
3: Does the traditionnal use of the inner race extractor (guillotine) harm the race if performed few times to achieve the figures needed?
 
Sergio said:
Looking at your pictures, I see outer race shims involved in your shimming procedure. On my present project I have to reduce the end float by about the same figures as yours. After inspection, both my Superblends have a very slight slide in the cases (no heat needed to drop the ice/cold bearings in the cases).
1: Despite outer race shimming a lot easier than the traditional inner race method, would you scare that possible bearing spinning could destroy the shims and debris come in contact with the rollers and destroy the bearing itself?
2 : Would you just put some Loctite in the cases to prevent spinning and if so, what about the bearing extraction if needed in the future?
3: Does the traditionnal use of the inner race extractor (guillotine) harm the race if performed few times to achieve the figures needed?
Click to expand...
A light dab of Loctite 609 on the outer races would work, can be heated to remove in the future.

If you have access to a junk set of superblends you can relieve the inner and outer races for easy slip on/off while dialing in your endfloat (use the outer race shims shown by TW, not the inner race shims)

edit: not sure where you are, but if near the GTA I can lend you my junk superblends used for this very operation
 
Bernhard said:
OK FE, the middle ground is as stated 0.005 to 0.010 on the page that I read, so, do your own sums!
Click to expand...
My point is, and being in agreement with Greg Mash, the quoting of numbers alone, from any source, is futile given the numerous different quotable sources that give very differing figures.

Hence Glens point regarding Comoz’s input. His input is based on physical evidence, and much experience.
 
Last edited:
Littlefeat, to get the most useful answers you really need to try and qualify your statement regarding the amount of play.

Is it really 1/8” ? That is definitely too much. Yiu might be putting side load on the rods or pistons, you’ll likely be giving the oil pump drive a hard time, And your primary drive alignment is gonna be all over the place. Plus the thought of the crank hammering side to side that much would make me concerned for the cases.

You don’t necessarily need a dial gauge for this, a steady hand and a vernier will give you an accurate enough measurement for this purpose.
 
Sergio said:
Looking at your pictures, I see outer race shims involved in your shimming procedure. On my present project I have to reduce the end float by about the same figures as yours. After inspection, both my Superblends have a very slight slide in the cases (no heat needed to drop the ice/cold bearings in the cases).
Click to expand...

I machined dummy bearings for checking purposes but it was not recommended to use shims behind the inner race although that method is used to shim Ducati crankshafts.
The bearings should be an interference fit in the case (which is not that high from the factory)
Perhaps you could clean both the case bore and bearing outer with Acetone and use Loctite 290 afterward with a weight on the bearing (which I use when heated to stop any creep)

I do not cool bearings feeling it is a waste of time and if not dried off can introduce condensation as soon as they get near the heated case, the heat transfer would be instant anyway.
The dry room temperature (unless you live in Alaska or Sahara) bearings should drop into a heated case easily (then weighted until cold > imho)

It might be worth having the case bores measured for round and size compared to the bearing OD to get a better idea of what you have ?

Sergio said:
3: Does the traditional use of the inner race extractor (guillotine) harm the race if performed few times to achieve the figures needed?
Click to expand...

I grind the inners (boilermaker) until I can remove the bearing easily but is not something I would recommend, but eliminates any chance of drag across the sealing surface and minimises drama to the interference fit on the crank for a new part.
People have been beating them on and off for decades and no doubt they were fit cold at the factory all the same.
I try to show some mechanical empathy to these old bikes.

#
You can not have 0.125" end float (unless it is a early 850 crank in a MkIII case or there is some massive wear that has been fine since 1982 based on the OP first post)
It is probably more like 0.030" which by hand feels very loose, even the 0.012" I shimmed to feels like double that without the dial gauge verification.

Old Britts made it easy to shim the crank by supplying them as packs.
Measure end float before splitting the cases, add the required shims at new bearing installation (after measuring the thickness of the old and new bearings)

Crank movement


Crank movement
 
Last edited:
Time Warp said:
I machined dummy bearings for checking purposes but it was not recommended to use shims behind the inner race although that method is used to shim Ducati crankshafts.
The bearings should be an interference fit in the case (which is not that high from the factory)
Perhaps you could clean both the case bore and bearing outer with Acetone and use Loctite 290 afterward with a weight on the bearing (which I use when heated to stop any creep)

I do not cool bearings feeling it is a waste of time and if not dried off can introduce condensation as soon as they get near the heated case, the heat transfer would be instant anyway.
The dry room temperature (unless you live in Alaska or Sahara) bearings should drop into a heated case easily (then weighted until cold > imho)

It might be worth having the case bores measured for round and size compared to the bearing OD to get a better idea of what you have ?



I grind the inners (boilermaker) until I can remove the bearing easily but is not something I would recommend, but eliminates any chance of drag across the sealing surface and minimises drama to the interference fit on the crank for a new part.
People have been beating them on and off for decades and no doubt they were fit cold at the factory all the same.
I try to show some mechanical empathy to these old bikes.

#
You can not have 0.125" end float (unless it is a early 850 crank in a MkIII case or there is some massive wear that has been fine since 1982 based on the OP first post)
It is probably more like 0.030" which by hand feels very loose, even the 0.012" I shimmed to feels like double that without the dial gauge verification.

Old Britts made it easy to shim the crank by supplying them as packs.
Measure end float before splitting the cases, add the required shims at new bearing installation (after measuring the thickness of the old and new bearings)

View attachment 80178

View attachment 80179
Click to expand...
By measuring the end float before the cases are separated to determine if shimming is required, it would be possible to get a false reading if one of the outer races wasn't fully seated, quite possible if the proper fit is suspected ie heat not needed upon removal.
 
Last edited:
BERT said:
By measuring the end float before the cases are separated, it would be possible to get a false reading if one of the outer races wasn't fully seated, quite possible if the proper fit is suspected ie heat not needed upon removal.
Click to expand...

True (I removed the, and hope its right) but it could be that easy.

In that posters "case the bearings are already removed and they are the least of the problem if there is no interference fit in a cold engine case, even Loctite has its limitations with alloy to steel combined with heat expansion in a at temperature engine.
I guess as long as they do not rotate or creep, of course it was not uncommon for some folk to break out the centre punch/pop and go round the case bore on Brit bikes in general that suffered that problem.
 
Time Warp said:
True (I removed the, and hope its right) but it could be that easy.

In that posters "case the bearings are already removed and they are the least of the problem if there is no interference fit in a cold engine case, even Loctite has its limitations with alloy to steel combined with heat expansion in a at temperature engine.
I guess as long as they do not rotate or creep, of course it was not uncommon for some folk to break out the centre punch/pop and go round the case bore on Brit bikes in general that suffered that problem.
Click to expand...
Sorry Timewarp, I changed my last reply wording slightly for clarity.
 
Fast Eddie said:
Littlefeat, to get the most useful answers you really need to try and qualify your statement regarding the amount of play.

Is it really 1/8” ? That is definitely too much. Yiu might be putting side load on the rods or pistons, you’ll likely be giving the oil pump drive a hard time, And your primary drive alignment is gonna be all over the place. Plus the thought of the crank hammering side to side that much would make me concerned for the cases.

You don’t necessarily need a dial gauge for this, a steady hand and a vernier will give you an accurate enough measurement for this purpose.
Click to expand...
All roller bearing have some side to side play in them when worn, it could be that they have done a high mileage and worn both the needle rollers and the L face of the bearing housing, or even a (looser) non compliance bearing fitted that did not have the tight side to side clearance required.
 
My Atlas' crank has about 0.7mm end float. I bought the bike like this a few years ago and done more than 10,000km on it. No dramas.
 
acadian said:
A light dab of Loctite 609 on the outer races would work, can be heated to remove in the future.

If you have access to a junk set of superblends you can relieve the inner and outer races for easy slip on/off while dialing in your endfloat (use the outer race shims shown by TW, not the inner race shims)

edit: not sure where you are, but if near the GTA I can lend you my junk superblends used for this very operation
Click to expand...
This is a good suggestion, I have some used bearing in stock I could use for sure. Thank you Acadian for your offer to lend some. Further in this thread it is recommended to measure both used and new bearings for slight differences. Inner used bearings showed .0025'' thicker L (the part touching the crankshaft). So it makes a total .005''to take in account.
 
Looks like that .004 to .015 recommendation grew a bit from 2011 to 2015. Maybe that was the period where some tightly shimmed engines were found to have blue bearing races.
I set my 920 at .015".

 
I haven't seen (or I missed it) where the OP responded with an actual "measurement." So what's the actual float in metric or imperial units?

One thing occurred to me...when he said "side to side" I ASSumed he was referring to crankshaft end float but maybe he was talking about 'play' between the backward/forward motion of the crank?
 
Time Warp said:
I grind the inners (boilermaker) until I can remove the bearing easily but is not something I would recommend, but eliminates any chance of drag across the sealing surface and minimises drama to the interference fit on the crank for a new part.
People have been beating them on and off for decades and no doubt they were fit cold at the factory all the same.
I try to show some mechanical empathy to these old bikes.
Click to expand...
Thank you TW, sure I won't try to grind, I'm too old and shaky. Otherwise I see that you are reluctant to play with the inner as many other have the same opinion. My feeling was on this side too, so you insured me. Being without dial gauge, would it be accurate enough to use a flat feeler gauge between the flat boss in case and the flat cheek of the crankshaft ?
 
Time Warp said:
In that posters "case the bearings are already removed and they are the least of the problem if there is no interference fit in a cold engine case, even Loctite has its limitations with alloy to steel combined with heat expansion in a at temperature engine.
I guess as long as they do not rotate or creep, of course it was not uncommon for some folk to break out the centre punch/pop and go round the case bore on Brit bikes in general that suffered that problem.
Click to expand...
Thanks TW.
Looking for the Loctite 609 (green stuff) spec. I have found this link;
http://tds.henkel.com/tds5/Studio/S...at=MTR&subformat=REAC&language=EN&plant=WERCS
A chart shows Chemical/solvent resistance. The resistance of more than 1000 hours in oil environment at 125C (about 300F) is 100%.
Do you think our engines run at such temp? I have no clue....If engine runs cooler than that, I guess Loctite would not melt and the bearing move.
About the use of punch all around the case to prevent spinning, I'll stay away...I'm too old and shaky to make any attempt...LOL
 
More Jim Comstock info from the data base.
He mentioned that every Commando engine he had gone inside showed clear signs of the bearing outer races spinning in the cases.
Years ago, in an effort to stop that from happening, he tried the Loctite bearing retainer product on some mainbearings.
When those engines came apart later the bearing locker had not held.
He was trying JB weld as a bearing retainer of last resort, but I don't recall if that worked or not.
I think not.
The only way I know to really hold them from rotating for certain, is to stake the bearings with machine screws. I did this on my 1360 motor and it is a bit of a tricky procedure.

Glen
 
You must log in or register to reply here.
Back
Top