Primary cover bearing

78jotadave

78jotadave

Hero member
Location
Palm Desert, California. (near Palm Springs)
OK so I was doing an inspection inside the primary cover (will need a new chain soon). So the bearing in the cover the crankshaft one has some in and out play, the question is how much is OK, do I need to replace it ,the one for the clutch support has no slack moves freely. Any advice is welcome,  Cheers Dave.
 
Dave

My crankshaft outrigger bearing developed "some" in and out play and quite soon after that screwed itself right out through the primary cover, leaving a nice neat round hole. When I reported this on this forum a couple of other people had had the same issue.
Normally these things are an absolute buggar to get out. You have to heat the whole cover, and having a blind bearing puller also helps immensely. You do have a problem. Fortunately, you can probably fix it with a gap-filling product like Loctite 660 (if you can get it, OEM automotive only). Try calling Loctite customer support for a recommendation.
Or you can find a machinist, have the hole welded or bored and sleeved. But do it right away.

Ken
 
Dave, that's a big relief. Sorry, I don't know how you measure wear in the inner race in a needle bearing. But the inner race should be a tight fit on the end of the crank, normally needs a bearing puller to get it off. Is yours sitting in the bearing in the outer primary cover when you pull the cover off?

Ken
 
When I removed the cover the inner race that the needle bearing rides on remained on the crankshaft end. It shoes no significant wear. The bearing in the Primary cover is a firm fit its just that the needle roller part has some in and out play.  I compared it to a new needle bearing that I have had in my possession for 30 plus years and the new one has similar play so maybe this is normal. The new bearing is not identical to the one in the cover so I am not going to use it.

So if anyone has the primary cover removed from their bike now or soon take a look and let me know if the bearing in and out play is present, Thanks Dave
 
A little bit of in and out, side clearance on the rollers is ok. You can check for radial wear in this bearing by sliping the cover on backwards when the primary chain is off and giving it a wiggle.


  Keith
 
I have recently fitted brand new SKF bearings in the cover of my 750 and I can tell you that the play is present. Didn't measure exactly (I didn't know that you will ask the question  ;)) but the play is quite big, I'd say maybe almost a mm.
 
Thanks for the replies, the bearing measures up just fine, Kieth your tip was brilliant.
Oh another thing I just noticed is this bike has bolts and not rivets in the clutch housing. Did any of them come from the factory like this?  I have owned the bike for 27 years and it had 5800 miles on it when I bought it in 83. First owner purchased it from Slaters in the UK, Cheers Dave.
 
Hi Dave
My mate has had his 1978 gold jota from new and his primary was allready bolted when we replaced the damper rubbers so his must have come from the factory like it for some reason
neale
 
Dave,

While you're at it, closely inspect the roller needles.  Last two bikes that I pulled the primary case had a broken roller in one of the bearings (one at the mainshaft, one at the crank).  Won't be too bad short-term, but might ruin the mainshaft long-term.  Crank isn't so bad as the needle race can be replaced.

What bothers me is that I didn't find a cause for the failure!


The Mk II triples had bolted clutches, the factory apparently realised it made life easier.

piet
 
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