Bearing question

[ran49]

I'm thinking I may upgrade the jack shaft (clutch assembly shaft) bearings on my China 70 cc.
I noticed on my first motor these bearings were shielded as opposed to sealed.Sometime back someone recommended replacing them with sealed bearings.Any of you motorheads concur with this.Thanks Ron

[Can Harm Hen]

Do you know how to remove the bearing? The side of my bearing came apart and a couple of the ball bearings came out and got ground to dust.

[Norman]

to get the bearing out take off the sprocket and the clutch using the puller then with a plastic hammer or use a hard wood block tight tapping on the jack shaft form the sprocket side. To drive out the shaft the bearing on the sprocket side once the shaft is out you will still have the remaining bearing to remove it can then be tapped out by using a deep socket from inside the engines housing and light taping to drive the bearing out on the chain sprocket side.
Don't hit the jack shaft on the clutch side unless there is no other way to get the shaft out the center bolt that works the clutch will damage very easily. there is a machined shoulder in the engine housing that the bearing will seat against so these bearing will drive out one way only. you could use a press if you have one but I've found that going easy you can drive the bearing out with out damaging anything to install the bearing it just a reverse of the way you got them out.
I think I show most of this on the engine tear down post in the classic posts.
as for shielded vs sealed you can remove the shield on the inside of the bearing before installing them and get grease into the bearing from the lower clutch cable mount if you take it off you can shoot grease into the hole and get grease to the bearing with out removing the shaft. sealed bearing don't allow you to grease them and the shielded I think are cheaper. Just some useless info.
Norman

[europorsche914]

I replaced my bearings with SKF 6202-2RS bought em on ebay: skf 6202 2rs items on eBay.com

[Can Harm Hen]

Rats, I didn't know you could grease the bearings through the clutch cable mount. I replaced them with shielded bearings that are closed on both sides. Oh well, they were cheap. Let's see how long they last...

[toytime]

Interesting! I always wondered about those bearings. I drove mt last bike for over a year without touching them.
So you remove the clutch cable mount and pile grease in there? (I'd love to fill it up)
And can this be done on stock engine with factory bearings?

[Creative Engineering]

Originally Posted by toytime

Interesting! I always wondered about those bearings. I drove mt last bike for over a year without touching them.
So you remove the clutch cable mount and pile grease in there? (I'd love to fill it up)
And can this be done on stock engine with factory bearings?

I don't think it would be a good idea to fill it up!

More than likely this will cause your outer bearing seals to be pushed out; especially the independent type seals that I've seen on some of these engines.

Then there will be goo everywhere.

Jim

[Norman]

the shielded bearing are not sealed and the grease will go into them but you should remove the clutch completely and the sprocket side cover so you can see when the grease starts to come out that is the time to stop greasing it. I remove the inside shields on mine and then grease them. but to remove the inside shield you have to take the whole shooting match apart and put back together. the shields will then be on only the outside and if you take the whole shaft out you will get to see the real clutch spring and it can be tightened up a little bit for more clutch pressure. If you are going to take it apart take the whole thing apart and clean it up and grease all the things inside that make up the shaft. That big spring will remove and not explode all over the place but just looking at it you swear it will fly apart if you mess with it.
Norman

[Can Harm Hen]

There's no way I'm tearing it down again, unless I have to!
The only tool missing from my toolkit was a hammer, so I had to use a rock from my front yard to pound out the shaft and bearings, caveman style. It took me most of the weekend, but now I can say that I can change out clutch shaft bearings with nothing but a rock, a socket wrench, and a screwdriver.

[Can Harm Hen]

By the way, thanks for the great teardown guide, Norman.