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Honda single cam bearing solution-why not?

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There is a seat on the inside (cam side) of the cover. The bearing rides against the seal and the seal cannot get past the centrifugal advance so everything just stays in place. So far nothing has moved at all and probably never will unless the bearing seized up for some reason.

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I've just done a similar job on a CB125 motor but, being a marine engineer, it seems I've gone totally over the top as I didn't see this post till now.

Judging by the bearings that I saw on other camshafts I didn't think that the narrow bearings would be able to take the load so I made an outrigger bearing holder for a 6004 bearing that goes between the head and points housing and extended the camshaft to take the advance retard unit.

A lot of work was involved measuring up to get the whole lot as narrow as possible (it's about 23mm wide) and also to seal the shaft where it comes through the bearing. I'll do a write up on it sometime, I've only done about 100 miles on it so far but all good.

As it turned out, the head was ok, measured with go/no go gauges, it is actually the camshaft journals that are worn, 19.82 at the small end, 29.88 at the bigger end as opposed to 19.97/29.97 new I believe. Cost me about £30 for materials, a lot of time, then a NOS camshaft turned up on ebay for £45!!

Still, like drturnip I just wanted to see if it was do-able.

Great that folks can share their knowledge,

Thanks,

Craig

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I would like to see some pictures when you have time. I can't believe you squeezed a bearing that big in there!

Edited by drturnip

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I'll get something up in the next few weeks, I'll post it on a seperate thread with a link to yours as that's real ingenuity at work, I've got the benefit of a lathe to help me.

My bearing is in a separate housing between the head and the points housing. Your article has got me thinking that I could make a new points housing to take a bigger bearing and seal, that would narrow it right down. The limit on bearing width is imposed by the running face for the seal on the camshaft, from memory there's only about 9mm there once the points housing, which also acts as a thrust face for the camshaft axial travel, is fitted.

I'll keep you updated.

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Thanks. I wish I could find a wider bearing with integrated seal but to my knowledge there is no such thing, though I must say the bearing I am using seems to work fine.

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This problem would not have happing if you had been change your oil evey 1000 miles and ocen year or if put 3000 miles on it then you need claen out the oil pump and centrifigal oil filter rotor as well as flush out the crankcase crank case, clutch cover and the stator cover.

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I change my oil much more frequently than that. This is an old bike however and it was obviously not cared for properly along the way.

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I took it apart last week and inspected the bearing. Still spins as smooth as when I put it in. The oil seal weeps a bit but not enough to get excited about.

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Here is my trashed cam and head

bad bearing.jpg

cam.jpg

The dimensions of the cam cover seal are 15x25x7 (id x od x width)

I found that a 6802 bearing is 15x24x5 which is 1mm smaller in diameter and 2mm narrower (leaves room for a seal). I bought an enduro brand bearing from a local bike shop for $7 and removed its inner bearing seal so it could get oil from the cam oil hole. The bearing is rated for 33000 rpm and a max temp of about 250, which is probably too low. I have no idea if the load of the cam matches up with the load rating of the bearing. My guess is it is probably pretty close.

I went to ace hardware and bought some brass shim stock in varying thicknesses to make up for the 1mm smaller bearing diameter.

I cut out three srtrips of .005 in. one of .003 in. and one of .001 in., .018 in. total.

(1mm = about .039in). This left me with about .003 wiggle room (.0015 around the edge) to get the bearing in.

 

shims.jpg

I placed the shims around the outside of the cam cover seal housing starting with the .001, then .003., then the three .005. staggering the end points. I then pressed the bearing in and put a few drops of red loctite around the edge.

 

bearing in cover.jpg

This is the backside of the cover.

cover and cam.jpg

Here is is installed.

 

cover installed.jpg

I also installed a 15x25x4.5 seal. I had to trim the outside edge to make room for the advance mechanism. A 15x25x3 vc seal is available and would be perfect but it was a special order item from the local bearing place. As a side note watch Allied Bearing. They charged me a shipping handling fee. You are better off ordering from an internet provider.

Before installation I cleaned up the cam bearing surface and cleared the blocked oil hole. I also replaced the cam chain while I was at it. The cover goes on and off without tapping or prying but does have to be finessed a bit. The engine needs to be at TDC and the cam chain tension backed off, which makes sense. The bike runs excellent and is quieter. I can feel no play in the cam in any direction. I took the cover off to inspect the bearing after running it and it appeared to be getting a decent supply of oil. Time will tell if this lasts very long, but if I have to replace the bearing every so often big deal! In the mean time I will try to find a bearing of the same size with maximum load and temperature ratings, and get a narrower seal.

 

Edited by drturnip

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