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June 24th, 2004, 08:45 AM   #1
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to Roll or to Ball........

Dear members,

I really am sorry to bother you guys about a "beginners" question, but I have a "seed of doubt" in my soul.

I am overhauling my trusty Mr.Maximus (Hus.550´01 model)

Among other things I am replacing the connecting rod (It still is stock, as is the piston / rings ! )

My question concerns the main bearings:
Should I replace the standard ball bearings or should I go to the roller type bearings ??

It seems to me that the roller bearings are stronger, BUT will not "take an axial load" according to Vormanauk and Taffy.

So, which one is more reliable??

Heimir Bardason
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June 24th, 2004, 09:18 AM   #2
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The Cylindrical bearings are indeed superior to that of the ball.

Proper installation (Correct running clearance and alignment) of Cylindrical bearings is critical. Get it wrong and early failure is likely.

Ball bearings are far more tolerant regarding running clearance and axial alignment.

In short:
If you have the provisions to insure proper cylindrical bearing set up by all means use them. http://www.husaberg.org/modules/Gallery ... .sized.jpg

Hope this helps.

Kind Regards,
Dale
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June 24th, 2004, 10:08 AM   #3
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heimar

i got that one right then thor! anon

any kind of half decent tool makers will, if prepared to do a 'fiddly little job', be able to check your cases for trueness. take them to the toolmaker empty of everything - especially outside dowels etc. give them the crankcase screws and the dowels and they will check them.

someone came up with the info that there are infact oversize main bearings that are only .5mm or was it 1mm bigger than the originals. i'm speaking as someone who hasn't done this so it's only theory.

so you need to find out what you would do if the holes for the mains aren't true...

someone here will know about these oversize bearings i hope. UHE members....help!

the top of my cylinder has a drop from one half to the other that you can hook a finger nail on! so there is so much you could 'blueprint' if you wished too.

Taffy
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June 24th, 2004, 10:27 AM   #4
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As a result of each case section having a main bearing retention lip bearings or a suitable spacer must be installed prior to confirming axial main case bore alignment.

Cylindrical bearings can be ordered "ground to size" for compensation regarding variations in crankshaft axle OD and main bearing bore ID.

Spacers of varying thickness are used to control axial crankshaft float.

Lower end set up as described including custom ground main bearings runs aproxiamately $400.00 US


Hope this helps.
Best Regards,
Dale
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June 24th, 2004, 12:52 PM   #5
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I agree with Dale. If you measure accurately the ID of the Case and the OD of the crank, then you could supply this to the afformentioned bearing place and have them grind you bearings with proper preload.

What is preload? When you press the bearing into the case, the outer race with "shrink" a bit, lets say 0.001mm. When the crank is pulled/pressed into the bearing, the inner race will expand a bit, let's say 0.001mm. The balls within the bearing need a certain amount of room to rotate. If there is too much preload, then there is not enough room for the balls to rotate, and you will get premature bearing failure. Same goes if there is too much "slop" in the pressed surfaces.

I have a feeling, that along with the case alignment, that this may be a major hidden contributor to everyones premature crank bearing failure.

Dale, would you explain this statement a bit further:
"As a result of each case section having a main bearing retention lip bearings or a suitable spacer must be installed prior to confirming axial main case bore alignment."

What does one do if the cases don't align (would this not yield catastrophic failure straight from the manufacturer)? Is there a shim one would use to fix, or would one need to match up with another case?
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June 24th, 2004, 01:10 PM   #6
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Hi Luke,

Main bearings must be installed from the inside of each case halve.
Each bearing is pressed in until seated against a shoulder which is part of the main casting. The bearings are then retained via the crankshaft and said shoulder.

On rare occasion when the axial alignment is out of specification I use a fixture which indexes off of one case halve in order to bore the remaining case halve on center. This creates an oversized bore which requires an oversized outer bearing race. However, improper bearing fit, misaligned crankshaft halves and excessive end float are the most common cause of premature failure.

Hope this clears things up a bit.

Best Regards,
Dale

Ps
I have yet to encounter a set of Husaberg engine cases and / or a crankshaft combination which provides for the proper clearances when using off the shelf cylindrical bearings. I always end up using custom bearings.
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June 24th, 2004, 01:14 PM   #7
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Dale, do you space between the bearing and the case, or between the bearing and the crank, when the axial float is out of spec?
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June 24th, 2004, 01:29 PM   #8
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Originally Posted by Parsko
Dale, do you space between the bearing and the case, or between the bearing and the crank, when the axial float is out of spec?

Lineaweaver modified crankshaft and auxilary drive

Note bearing spacer and cylindrical main bearing inner race.

As pictured I make a custom spacer from bearing stock when removing the balnce unit. Otherwise I use OEM shims to control end float .

I average one maybe two crankshaft / case upgrades per month.

Dale
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June 24th, 2004, 01:54 PM   #9
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Jesus christ guys!!

Thanks for a fantastic response !

I will have to look into this matter with my space shuttle eyes.

I think Mr. Parsko might be right about this one, "that this may be a major hidden contributor to everyones premature crank bearing failure."

Now why does the manufacter not not do this in order to have a bulletproof crank/bearing assembly ???

Anywa, thanks again all you professors of the round table, and I´m going
straight to my belowed garage again.............

Best,

Heimir Bardason
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June 24th, 2004, 02:15 PM   #10
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Gentlemen,
With all due respect "this is not news"
Since early 2003 it has been common knowledge (at least I thought it was) that chronic main bearing failure was as a result of improper running clearance and misalignment.

Perhaps the earlier discussions were lost with the great crash of 2004.

Sincerely,
Dale
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