MC5 rear wheel bearings

[Lloyd Boland]

I was cleaning the bike after a recent race and noticed the wheel did not spin well after I cleaned it and lubed the chain.  I first thought that the rear brake was adjusted too tight.  I kept loosening the brake tension and no change.  It was so bad that if I spun the wheel it might do 3/4 to 1 revolution.  I pulled the rear wheel off and realized that the bearing were so full of gunk that the wheel would not spin.  I sprayed different solvents, ie WD40 into the bearing's and all kinds of dirt and grime came out.  I put the wheel back on and it spins very freely.  I now notice a little free play in the rear wheel after it is all tightened up.  My question is, if there is any free play in the rear hub, does that indicate that the bearings need to be replaced or something else?  If the bearings need to be replaced, is it a difficult job or can it be done at home without too much difficulty?
As always, thanks for the information in advance.

Lloyd Boland
1976 250 MC-5

[Lew Mayer]

There should be no free play in the wheel. Replacing them isn't too difficult. You can certainly do them at home.

Lew Mayer

[Lloyd Boland]

Thanks Lew.

Does anyone know the size of the rear wheel bearings, i'm assuming there are 2, and if they are a special "type"?  Do you just tap them out and tap them in once you remove the retaining clips?

Thanks again.

Lloyd Boland
1976 250 MC-5

[Rain Man]

LLoyd, look at the print in your parts book before ya start hammering away, there's 1 snap rings to deal with first,   6205 SKF bearings I feel are your best bet. The romanian bearings are for ski doo"s.  Rear bearings are a common problem, especially if you ride like the nuts I ride with.


Raymond
 Down East Pentons

[brokenb23]

Loyd, Some hubs 2 bearings. Some hubs will take 3. Bearing could be loose in hub. There is spacer between bearings.  I have succesfully shimmed bearings in the hub with aluminum from a Pepsi can
Bob Brizzee

[Mike OReilly]

My parts book lists them as 6303 2RS (which means 2 rubber seals). 2 only. They should be available at any bearing, industrial or auto supply house. There is one circlip on the R.H.S. which will need to be removed.
I can fax the blow-up if it would be useful. Get back to this post if there are any other questions.
BTW, the symptoms you describe mean that the bearings were well and truly cooked when they get to that stage. I'm headed out now to change front wheel bearings on my '76 250GS.
Mike

[Lloyd Boland]

Thanks everyone for the help.  I am assuming that once the circlip/snap ring is removed on the right side, the bearings are tapped out to the right?  Also, I don't know anything about the different types of bearings.  What's the difference between the 6303 2RS and the 6205 SKF bearings?  This week I will be a little tight on time to get any further on this project, my step-son is getting married this weekend and there always seems to be some fire that needs to be put out.  I will tear into it next week and give you an update.  As always, any additional suggetions are always welcome.
It is always nice to have the feeling that you have your own instructor there with you as you do these projects.  I am pretty good with the hammer, Special Yamaha Tool #1, but I don't want to mess anything up in the process.
Thanks again to everyone.

Lloyd Boland
1976 250 MC-5

[Lew Mayer]

A 6205 is another bearing altogether. The SKF is a brand,I believe.
When you drive out the bearings, the number you want, may be on the bearing.

Lew Mayer

[p3mn256]

lloyd  i just changed my rear wheel bearings on my 76 250 mc5 they are   6303   2 only.  look in side the spacer tube on one end there is a notch to use a punch on the notch is on both sides on one end .

steve barber

[Mike OReilly]

Why did the Germans (Austrians - same difference) make some of these assemblies so complicated. I just finished the front wheel bearings. More spacers, bushings and shims than you can shake a stick at. A Jap front wheel would have 2 seals, 2 bearings, a spacer and maybe a circlip. It's the same with other stuff too. The Japs could mount the engine with bolts and tabs on the frame. Of course KTM felt that need to go with threaded bushings etc. at the rear mounting, which of course when not maintaned allowed play which in turn damaged the cases.
I remember getting my '78 IT 175 and marvelling at the fact that someone (other than an autocratic Teutonic engineer) had put some thought into ease of maintenance ie: change an air filter with no tools; not have spacers and washers all over the ground when changing a rear wheel. Anyway...that IT is a distant memory and the garage is still full of Pentons so I guess that says something...at least until the day comes that I have to do crank bearings. A whole other story.
Mike

[Mike OReilly]

Back to the rear wheel: (which is a whole lot simpler than the front BTW):
The 6000 series are universal part numbers for bearings. ie: the front wheel takes 6003's.
The L.H. bearing gets driven out the left side and the right. Doesn't matter which goes first. As noted, you reach through with a punch fromt the other side. Either force the spacer off centre or find the notch referred to.
To re-install the bearings, put them in the freezer for a couple of hours which will shrink them. Drive them in being careful not to apply too much pressure (or none) to the inner race. A large socket or the old bearings are useful as drivers.
And man, that business about other pressures and obligations - can I relate. You start a project and, can it really be that long to get back to it. Good luck.
Mike

[Lloyd Boland]

Thanks Mike.
I couldn't wait until after the wedding.  Kept thinking about the bearings.  Monday night, very late, went out to the garage and took off the wheel and removed the bearings.  Thanks for the tip about the notches in the spacer to drive out the bearings.  Went to the local bearing shop and picked up 2 new bearings, cleaned the hub real good and installed them late last night.  Everything went without a hitch (for a change).  Thanks for all the help.

Lloyd Boland
1976 250 MC-5

[Rain Man]

Woops Lloyd, I apologize for the confusion with the wheel bearing number (6205)[:I].  I thought I had it memorized,then I realized that bearing size fits the snowmobiles. Mr. OReilly used his head and looked up the bearing in the manual,  one "atta boy" for you Mike for keeping the information right !![8D]

Raymond
 Down East Pentons