bearings

[Len Matthews]

A word of caution about using a sealed bearing. I found that the flat face of the inner race was smaller in diameter compared to a normal bearing. That meant the contact area between the back of the sprocket ET60/1 and the bearing was much reduced, resulting in rapid wear at that point causing the sprocket to move inwards; so much so that the inside links of the primary chain were chafing on the radial ribs that surround the bearing housing. In turn that meant a misaligned primary drive. So, back to a normal bearing for me.

 

[stumpy lord]

A word of caution about using a sealed bearing. I found that the flat face of the inner race was smaller in diameter compared to a normal bearing. That meant the contact area between the back of the sprocket ET60/1 and the bearing was much reduced, resulting in rapid wear at that point causing the sprocket to move inwards; so much so that the inside links of the primary chain were chafing on the radial ribs that surround the bearing housing. In turn that meant a misaligned primary drive. So, back to a normal bearing for me.

Hi,
both roger and I have found this to be problem when using modern sealed bearings in vincent crank cases. This could be one of the reasons why Roger suffered a broken primary chain ,and smashed cases, and no we were not using a clapped out primary chain.
My advice for what it is worth is to find bearings that have as little lead in as possible on the central boss for your main bearings. allso if you are in any doubt to the age and condition of your primary chain then change it, especially if it is a renolds. Burst crank cases are awfully expensive to repair.
stumpy lord.

 

[clevtrev]

A word of caution about using a sealed bearing. I found that the flat face of the inner race was smaller in diameter compared to a normal bearing. That meant the contact area between the back of the sprocket ET60/1 and the bearing was much reduced, resulting in rapid wear at that point causing the sprocket to move inwards; so much so that the inside links of the primary chain were chafing on the radial ribs that surround the bearing housing. In turn that meant a misaligned primary drive. So, back to a normal bearing for me.

A bigger problem is the amount of radius that has been applied to the bore, leaves virtually nothing for the PD2 to sit on. For my own use I machine the radius out and fit a spacer in the counterbore.

 

[Howard]

I'm confused again. I'm going to start signing as "Confused of Stoke".

Why would anyone want to put sealed bearings on a crankshaft?

OK, maybe on a racing engine, which may be a hard duty, but relatively short distances between rebuilds. But do we really want a bearing that has the same "smear" of grease for the whole of its life? Even the least travelled of us change the oil every year.

H

 

[Len Matthews]

Howard, the reason some people have used sealed bearings is to prevent oil transfer from crankcase to primary chaincase but there is a price to pay (See my previous post)

 

[Howard]

Howard, the reason some people have used sealed bearings is to prevent oil transfer from crankcase to primary chaincase but there is a price to pay (See my previous post)

OK. I forget I've always had a proper seal there on my twin.

The problem is, sealed bearings aren't realy designed for that sort of duty, they're more intended for applications where you can't relubricate easily, and the seals are to keep the grease in, and the dirt out. I use bearings with a single seal to back up an outside lipseal, but I always leave the inside seal out so that oil can get in. The seals in bearings aren't very effective once the grease gets old and hot, but when all the grease has run out they are effective at not letting engine/gearbox oil in.

I'm assuming by sealed bearings we're talking numbers with suffix 2RS.

H

 

[davidd]

Howard,

I cannot speak to the life of a sealed bearing compared to a non sealed bearing. However, I think that there are few if any individuals that would have a problem with either, but it is certainly a risk considering the effort to fix a potential problem.

If you ask the bearing techs, they say that if you pry out one seal you will substantially reduce the life of the bearing no matter how clean the engine oil is. If this is to be believed, it seems that it is better to run the sealed bearing as is or stick with the unsealed bearing.

I agree that a race engine is something that is more prone to rebuilding, but some of these engines go several seasons with the same lower end. I have done this only on a single and the E216 spacer has never displayed any wear.

David

 

[Hugo Myatt]

OK. I forget I've always had a proper seal there on my twin.

The problem is, sealed bearings aren't realy designed for that sort of duty, they're more intended for applications where you can't relubricate easily, and the seals are to keep the grease in, and the dirt out. I use bearings with a single seal to back up an outside lipseal, but I always leave the inside seal out so that oil can get in. The seals in bearings aren't very effective once the grease gets old and hot, but when all the grease has run out they are effective at not letting engine/gearbox oil in.

I'm assuming by sealed bearings we're talking numbers with suffix 2RS.

H

Now I know nothing of the intricacies of this but those with long memories will remember from MPH that it was just such a sealed bearing that caused the oil level in my Rapide's gearbox to rise dramatically. How? The seal worked as an excellent diaphragm valve and transferred oil and pressure into the chaincase (which I had sealed brilliantly) on the pistons down stroke and closed neatly on the upstroke thus exponentially pressurising the chaincase and so forcing the oil into the gearbox.

 

[Howard]

Hi Hugo. Is that for or against?? I think I'd prefer to drain the chaincase occasionally.


Hi David. Several seaons isn't a lot of miles compared to a tourer's miles. Ask "bearing techs" and they'll quote the company line for fear of being sued!! Take a seal out and you're not using it for it's design purpose (according to the catalogue). While the lubrication may, arguably, be worse after you remove the seal, long term it will only get better compared to a deteriorating blob of grease.

My comments are only to promote discussion here, but they are based on 20 years experience in the design of (industrial) power transmission systems.

H

 

[Hugo Myatt]

Hi Hugo. Is that for or against?? I think I'd prefer to drain the chaincase occasionally.


Hi David. Several seaons isn't a lot of miles compared to a tourer's miles. Ask "bearing techs" and they'll quote the company line for fear of being sued!! Take a seal out and you're not using it for it's design purpose (according to the catalogue). While the lubrication may, arguably, be worse after you remove the seal, long term it will only get better compared to a deteriorating blob of grease.

My comments are only to promote discussion here, but they are based on 20 years experience in the design of (industrial) power transmission systems.

H

Hi Howard,

I guess this is against. On a trip from London to Liverpool for the TT I had to drain the chaincase of a large quantity of oil and replace it in the oil tank at every service station on the way and on the way back. Kinda spoilt my holiday.
The mystery of the rising oil level in the gearbox was solved with a suggestions from the Prof. As I said I had gone to a great deal of trouble to make the chaincase completely oil tight including the dynamo housing. I tried the following experiment. I removed the gearbox oil cap and dip stick and fitted a condom over the filler neck. I rode the bike around the local block, about a quarter of a mile. The amount the condom had expanded in that short distance was staggering. It had turned into an enormous balloon and was pushing my foot off the footrest. Whilst this says a lot for the manufacturer of the condom it also demonstrated just how much the chaincase and gearbox were being pressurised.

Hugo