EC 300 '08 main bearings, piston

[5valve]

Bike has more that 300hrs.
Since I got the bike, did 2.000 kms on it. Ride mostly slow stuff, but don't hesitate to pin it.
Short time after purchase, 1 year ago, I noticed free play on ignition side.
https://www.youtube.com/watch?v=gqW0FSZ51Ow (crank the speaker volume from 0:35 onward)
Some mecs said its no big deal, so I rode it normally and checked every ride, if it had gotten any worse, but it didnt.

In recent times, cold bike starting took longer than 1 - 2 kicks.
Also was loosing a lot of bottom end torque, especially in tight stuff, when heat generation was higher, so I decided to tear the engine completely, re-piston and re-bearing it, and while at it, drop in checkpoint offroad's alu impeler and 80mm server fan on rectified DC, to make things cooler.

Installed was wossner piston "B", which should be 71.94. Through use, it was beat to 71.88, while bore was measured at 72.02.
Piston replacement just came in today, wossner C, or 71.95.

Main bearings were probably never replaced. Units were balled and sealed SKFs, Italy C4 ignition side, India C3 clutch side.
While clutch side bearing was in excellent condition, ignition side also had no visible deterioration, except for increased radial play.

Original bearings are, due to current gasgas insolvency undeliverable, and tad pricey.

You can get ordinary skf 62/28 C3, but you can't get C3HN3 version.
Also, you can get 6206 in C4, but you can't get ITN9/C4GJN version.

Surfing resulted in:
62/28 C3HN3 (clutch side)
- 62/28:...........size
- C3:...............clearance
- HN3:.............W18Cr4V (Rings, rolling elements, made of hardening bearing steel)

6206 ITN9/C4GJN (flywheel side)
- 6206:...........size
- (I?)TN9:.......polyamide plastic cage
- C4:..............clearance
- GJN:.............Bearing with high temp grease -30 to +150 ?C

The only thing worth worrying about, when buying (high quality) replacement bearings in the local store, is to get the HN3 suffix.

Since I will remove seals from bearings, there is no need for GJN, or grease.
Also, polyamid cage TN9 can be replaced with steel one.
There are + and - for using each type, like:
steel has longer life, but if disintegrates, cylinder, piston etc is toast.
plastic has less rotating mass and can run with lessened lubrication, but it's running life is supposed to be shorter.

There is a prolongued waiting time on C4 plastic cage bearings. Still, would rather use plastic.
That's it for now.

[5valve]

Pinpointed the area of crankshaft's radial play on rotor side.

Replaced crank bearings, clutch side C3, rotor side C4.
It's the C4 bearing's inner race, that has axial play.
Old and new bearing have the same amout of it.
If I pull the crank axially to the rotor side, radial play is gone, probably because bearing's inner race is stabilised axially.
If I push it to clutch side, radial play appears.

Has anyone used C3 bearing (6206 ball) on rotor side to correct this issue?

Engine blocks were assembled with much care and with use of tensioners and separators, rather then hammer and screwdriver.

[jostby]

Do you mean horizontal play, in and out? If so it's not to worry about. My '00 uses the 6206 on the ignition side. It has lateral (in and out ) but very little radial play. I don't know if a spec is called out in the manual. If nothing else it should be similar to the CR250, might be easier to find a spec for it.

[5valve]

Yes, it has horizontal play, exactly the amount of the inner race of the ignition side bearing play . But what worries me is that this horizontal play allows for vertical play on ignition side. It doesnt go away with engine heat expansion.

[5valve]

Pure assembling mistake. No play now.

[stian]

Originally Posted by 5valve

Pure assembling mistake. No play now.

So you ended up with SKF bearings?

(clutch side) 62/28 C3HN3 = > C3 62/28 HN3 (W18Cr4V?)
(flywheel side) 6206 ITN9/C4GJN => C4 6206 TN9 GJN

Im in the same situation.

[5valve]

I used NTN and INA, steel cage, is what the cheapest supplier could offer. 16? both.

[stian]

Originally Posted by 5valve

I used NTN and INA, steel cage, is what the cheapest supplier could offer. 16? both.

Aha. Sitting here with the SKF catalog in my hands, and it may as well be me, but I cant find bearings with the specifications.

Would you mind writing the product codes for the bearings? If you have them?
Thanks

[5valve]

Those are non obtainable through standard dealers, as they are oem protected, so you wont find them in any catalog. I cant really give you codes, because there arent any. It is just plain 62/28 C3 and 6206 C4. Just make sure it is a good brand and not fake.

[stian]

Originally Posted by 5valve

Those are non obtainable through standard dealers, as they are oem protected, so you wont find them in any catalog. I cant really give you codes, because there arent any. It is just plain 62/28 C3 and 6206 C4. Just make sure it is a good brand and not fake.

Ah, Ok. Thanks. Ill take a look at the catalog and find my closes bet. Ive got a lokal SKF dealer.

Thanks a ton thought!