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
JBSracing

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?

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?