Timing side 850 Commando new Superblend bearing too tight

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Drummer99

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I installed 2 brand new superblend main bearings in 850 commando cases and assembled the cases and crank to check end play. The crank would not move laterally. I disassembled and found the timing side bearing so tight that I had to work the crank back out of it. I removed the roller from the case allowed it to cool and it fits on the crank fine and comes off with normal pressure. I measured the case and the bearing with a vernier caliper it looks like about 8 thou difference Don't know if that is within tolerance however it seems like the case is crushing the bearing race in as it cools Any thoughts on this would be appreciated. Bearings have brass holders and are fro a reputable source I have never had any problems with them before

Drummer99
 
Drummer99 said:
I measured the case and the bearing with a vernier caliper it looks like about 8 thou difference
Click to expand...

Typical cold interference fits between an alloy housing and a steel bearing are 1.5 to 2 thou at these bearing sizes ie the bearing OD should measure 1.5 to 2 thou larger than the housing ID. 8 thou is excessive interference but measuring ID's at home can be am issue accuracy wise compared to measuring OD's. You need to measure both bearings and both housings to see where the issue is, ie a rogue bearing OD or the housing has distorted.

Also what is the bearing internal interference fit, C3 is the preferred clearance and is looser than the standard CN.
 
What make of vernier caliper are you using? some of the cheap digital ones can be adversely affected by temperature and there calibration can be suspect. measuring dimensions such as this (bearing registers and the like) i favour using either internal micrometers or snap gauges and an external mike, making sure that they are calibrated correctly.
I know this doesn't help you with your problem, but are the bearing registers free of burrs and are clean and true?
How was the inner race removed from the crank? I have seen numerous cranks where someone has used a chisel to get the inner race moving off enough to get a lever under it. Leaves a sorry mess that can throw the new bearing off.
 
As every british bike(norton) mechanic knows( or should know) bearings are designed into steel or iron housings. This is paraphrased from bearing manufacturer tech sections if you need to see it...Aluminum is a special non standard case. and therefore I am in full agreement with kommando above. However the OD shrink fit in the aluminum cases makes C3 clearance specificately needed for this reason. I have gotten very tired of redoing the main bearing job because of std clearance bearing being tight. I no longer accept std bearings for NHT builds. I'm especially annoyed at parts sellers that can not tell the difference. Unfortunately old stock marks C3 only on the package, but most of todays manufacturers mark C3 on the bearing race too!

If you use a chisel instead of a proper bearing puller than live with the results!
I routinely pull and press bearings on cold without any damaged .
Also remember the NHT crankshaft diameter change around ?71. Makes no difference with C3 bearings...for any NHT crank. M7 through Estart.
At least that what I have experienced...
 
Last edited:
dynodave said:
As every british bike(norton) mechanic knows( or should know) bearings are designed into steel or iron housings. This is paraphrased from bearing manufacturer tech sections if you need to see it...Aluminum is a special non standard case. and therefore I am in full agreement with kommando above. However the OD shrink fit in the aluminum cases makes C3 clearance specificately needed for this reason. I have gotten very tired of redoing the main bearing job because of std clearance bearing being tight. I no longer accept std bearings for NHT builds. I'm especially annoyed at parts sellers that can not tell the difference. Unfortunately old stock marks C3 only on the package, but most of todays manufacturers mark C3 on the bearing race too!

If you use a chisel instead of a proper bearing puller than live with the results!
I routinely pull and press bearings on cold without any damaged .
Also remember the NHT crankshaft diameter change around ?71. Makes no difference with C3 bearings...for any NHT crank. M7 through Estart.
At least that what I have experienced...
Click to expand...
I used a proper bearing puller to pull the bearing off the shaft Shaft was smooth and clean I will check the actual bearing for C3 tomorrow I have used these same bearings before with no problems I agree with you on the Vernier as I don't have an inside Mic I will get the case and bearing measured accuratel
 
Good luck.
Unless it is on the original box of the bearings that you actually installed, or marked on the race, I do not think you will be able to measure the 5-7? microns of difference that make up the clearance difference. I know I can't. But when I KNOW they are C3 they seem to always work as they should.

Interesting when installed in hot cases, while still hot you would think they are OK. Next morning and cold they are tight. Just think trying to start that engine at freezing outside with real tight bearings. I've run my nortons at +5f through +15F.

Parts sellers: Fool me once shame on you, Fool me twice shame on me! No C3...no money!
I have a pair of std to sell cheap, no return, no refund. I have no industrial machinery to rebuild.
 
If you have the old inner race you can measure it and compare with the new race; I can't say if measuring the new, installed, race will have an OD influenced by being fitted.

If the rest of the bearing is still fitted to your case then try the old race for fitment, it should fit "snugly" but without force. These procedures should give you a better idea of where the tightness is located.

Best.
 
"I can't say if measuring the new, installed, race will have an OD influenced by being fitted." OD and the ID... Of course it will !!
Measuring process is the main and only difference.


Bill I don't personally know if the C3 for a 72mm bearing clearance is factory selected by custom matching components to obtain the .00039-80" C3 extra clearance. How would you measure accurately a CN bearing with almost no clearance and max 1/2 thou. ID of the outer race, rollers, OD of the inner race?
Certainly not with verniers. Probably not shop micrometers either.
 
dynodave said:
Bill I don't personally know if the C3 for a 72mm bearing clearance is factory selected by custom matching components to obtain the .00039-80" C3 extra clearance. How would you measure accurately a CN bearing with almost no clearance and max 1/2 thou. ID of the outer race, rollers, OD of the inner race?
Certainly not with verniers. Probably not shop micrometers either.
Click to expand...

I bow to the depth of your experience and savant-like approach; fortunately I have not had any issues with new C-3 spec bearings; if or when I do and couldn't figure it out you'd be my first call, I greatly appreciate the time you have given me with past problems. Many thanks Dave!

The goal of my post was to, possibly, stimulate the OPs approach, maybe add a grain that would help him see the issue in a slightly different light. If this were me I would purchase another bearing and measure the IDs and ODs with my calibrated Starrett mics, I would put the mics and the pieces to be measured in the same space and leave them at the same temperature for at least an hour, I would make at least 10 measurements of each piece (or more) until consistence surfaced. If I had any doubt about the measurements I would walk down the complex driveway to the machine shop I use and ask them to do the measurements; they routinely work to 4 and 5 digits to the right of the decimal.

When my mind starts loosing digits to the right of the decimal point I'll know it's time to start concentrating of riding and sex...

Best.
 
Thanks for all your input I remeasured the bearing and the Timing case It would appear the difference is .002" I reheated the cases to 350 degrees and dropped the bearing in. I allowed it to cool until warm to the touch and then put the crank in and bolted up the cases. While warm I could move the crank by hand. I measured the end play it is about .014 ''. Once the case cooled to room temperature around 65 F I could no longer move the crank by hand but can leverage it easily with a screwdriver side to side still around .014". So I think I will be Ok as the crank turns quite freely and will losen up as it comes up to temperature. Does .014 sound excessive ? Should I shim it down to about 5 to 7 ? Thx Drummer99
 
14 thou is not excessive, the perfect copy of a skipping rope the crank follows at high revs means 14 thou is needed.

I would still remove that bearing, it sounds like a CN fit and needs to be C3, chances are when tight the rollers will skid instead of rolling and wear the roller journal surface . Did you check the markings on the bearing for the fit stamp.
 
kommando said:
check the markings on the bearing for the fit stamp.
Click to expand...

With the older fag bearing the box was marked C3 but not the bearings. More recently, the NTN boxes were marked C3 as well as the bearings.
Not sure what current FAG markings are.
I don't like to do an install just to test the clearance...I won't use the bearings I have to screw driver push to check end float.
 
Ok there is no C3 written anywhere on the case or bearing The bearing number is NJ306-E-XL-M1 It is a FAG bearing made in India The bearing outer dia was 72mm
 
Ok I went on line and found the same Bearing number but marked C3 It goes on to say the C3 bearing has greater radial clearance I now understand what you are talking about re C3 bearings So I should source a C3 bearing and replace it?
Drummer99
 
I had a UK supplier whose initials are LE tell me that a C3 bearing was wrong for my 70. He sent it to me anyhow, but that's the last thing I got from him. He gave me a big ration of crap about it.
 
I fitted C3 bearings to a set of maney cases and found the fit very tight when the crank was fitted leading to difficulty in finding the correct end float
 
Just a quick question. Are all the fasteners associated with the crankcase present and properly tightened? I ask because a number of folks will screw the lower end together without the 3 bolts the attach the engine to the cradle and without the 3 bolts that attach the engine to the front mount. You can use the bolts you have, but they will need spacers or washers to make up for the cradle and/or the front mount if you choose to not attach them at this time.

If your crank is still hard to turn with all fasteners present the C-3/non C-3 bearing question will come to the fore front.

Best.
 
The last few times I have assembled my engine -even with C3 clearance bearings -they were very tight and required literally screwing the drive side case over the inner race. Warm the cases to 100 degrees F. and then they slide together no problem.

And the motor has run that way for upwards of 50,000 miles with no signs of distress, so I don't worry about it any more.
 
Well you beat me to it. When I put my motor together I did it at 7 end float with C3 FAG. Next morning I noticed it was pretty tight but it would rotate
and barely slide left and right. Later that day it was easy to pull left and right and spun no problem. Realized no heat at night and the basement would
go down to 55 and daytime it heated up past 70.
Touch a large block of wood that all is well after 6k miles and will remain so.
 
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