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May 23rd, 2005, 07:25 AM   #1
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Bearing clearance

I have stripped a 2003 650 motor which has had the roller bearings replaced with balls by DCR. It has a 6206-C3 bearing on the magneto side and a 6206-C4 on the drive side. It is common place to use C3 clearance bearings on a 2-stroke for reasons of lubrication, and I can see why you might want a C3 in the Husaberg for reasons of flex and hot running, but C4 is rare even in 2-strokes. Can any body tell me what the pre-roller Husaberg 650 engine OEM bearing clearance was?

Many thanks.

FYI – If bearings aren’t your thing

C3 is an internal clearance, or the amount of internal free space between the rolling elements and the raceways of a bearing. The ranges of internal clearance are governed by ISO and the ABMA and are denoted by the ARB suffixes: C1, C2, C3, C4 and C5, where no suffix indicates normal clearance. C1 is a range less than C2. C2 is a range less than normal. C3 is a range greater than normal, C4 is a range greater than C3 and C5 is a range greater than C4. Tightest…..C1-C2-Normal-C3-C4-C5…..Loosest.

Ben
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May 23rd, 2005, 08:37 AM   #2
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Do you think that the rebuilder may have done a good job and measured the shaft, possibly finding it oversize, and thusly ordered oversize bearings so the preload would still be the same?

-Parsko
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May 23rd, 2005, 09:05 AM   #3
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The C #'s refer to the fit between the balls and the inner and outer races, not the fit of the inner race on the shaft.Since Dale has found that often the cases are not matched perfectly in respect to the bearing seats ,this main bearing with greater than normal clearance is no doubt an attempt to allow the crank and crank bearings to survive at some position other than the perfect horizontal state.....nsman
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May 23rd, 2005, 02:04 PM   #4
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...The values for radial internal clearance are given in table 3. They are in accordance with ISO 5753:1991 and are valid for unmounted bearings under zero measuring load....

Hence my point. The inner race will expand when pressed onto the shaft. This might turn a C4 into a C3, if the shaft was oversize.

Regardless. DCR simply may have not noticed, or cared. In the grand scheme of things,

C3-15 to33 (0.0006-0.0013)
C4-28 to 46 (0.0011-0.001

We're talkin microns here.

Depending on how you look at it, cause 30mm bore is on the transition.

If you change the bearings once a season (as we are supposed to do then it shouldn't matter, IMHO).

JBS- Dan at Motoxotica (or another dealer) might have one in stock that they could pull and check the numbers on the bearing itself.

-Parsko
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May 23rd, 2005, 02:12 PM   #5
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Hi Ben,
C3 has been the Husaberg standard since inception.

Perhaps KTM has finally recognized (ie taken my advice) the main bearing issue and this is their first step.

If such is a result of DCR then he is indeed traveling in the correct direction.

Best Regards,
Dale
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May 23rd, 2005, 03:04 PM   #6
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Thanks for all the responses.

Dale - thanks for the info on Husabergs history of using C3 clearances. It was as I suspected, some of the gear box bearings were C3 as well but not all, I guess some were OEM and others had been replaced. Clearances aside, when you speak of the "main bearing issue" do you feel, as I do, that the mains are rather small for the job in hand.

All be it that they are adequate, in that they run perfectly well, I feel that the Husaberg would gain more than it would loose if had bigger mains. I feel if I were the design engineer at the inception I would have gone bigger, is there some historical reason for the size way back at the birth of the Husaberg?
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May 23rd, 2005, 03:55 PM   #7
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Originally Posted by JBSracing
All be it that they are adequate, in that they run perfectly well, I feel that the Husaberg would gain more than it would loose if had bigger mains. I feel if I were the design engineer at the inception I would have gone bigger, is there some historical reason for the size way back at the birth of the Husaberg?
Hi Ben.
The engine was originally designed as that of 499 cc. The objective was to manufacture a powerful, compact and lightweight unit construction single. Peak torque was in the high thirties and rpm limited to that of 8500. Needless to say the bearings in question were more than up to the task @ hand.

Best Regards,
Dale
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May 23rd, 2005, 04:14 PM   #8
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Yeah, some thing like I thought. Thanks Dale.

Zabel 2-stroke sidecar engines have been mentioned hear a few time. They have a similar story, they are based on the Maico MX 500, which in its own time was based on a beefed up MX 250 bottom end. One of the left overs from its history is that the MX 250 had a 18mm little end pin, fine, the MX 500 had the same 18mm little end pin, OK, the Zabel 700 has an 18mm little end pin and has "mysterious" piston fails and a piston life of 4 hours.

Are Husaberg likely to make any moves to address the mains for 650's? What mains do KTM 525's run?
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May 23rd, 2005, 04:40 PM   #9
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