Cam bearing shields

Coastie · Jun 24, 2010

Hi Guys

Is it better to put shielded or open bearings on the cam?
I know the early girls had them open but I've heard the later years had shielded installed.
What's better and why did they change?

Coastie

ned37 · Jun 24, 2010

your choice. since the later replacements are sealed, perhaps the engineering people are trying to tell you what they think.

Taffy · Jun 24, 2010

seals in for sure at the back while at the front I'd leave them off as there is plenty of lube. fact is all open balls are really loose later on.

regards

Taffy

bushmechanic · Jun 24, 2010

leave em in keeps the big bit of snot out

the guys trying to get 30-40 000 Miles out of their RFS's found the cam bearings last longer with the seals on.

Coastie · Jun 25, 2010

Thanks guys.
I agree that leavin em in would have to keep all the crap out but just a bit worried about the grease they come packed in comin out and no oil gettin in.
I don't know how the sealed bearings compare as I've only run opens in there.

Hey Taffy
What side are you calling the "front"?
What's the theory behind takin 1 side off?

Coastie

Taffy · Jun 25, 2010

when feeding the cam chain that is the nearest side to me. I'm talking about the whole of the far bearing being sealed and the whole of the cam bearing at the cam chain tunnel being open. they always fail at the back where the oil can't get too.

I used to take one side off - thats in the doc isn't it? the idea was to keep debris from getting in.

regards

Taffy

bushmechanic · Jun 25, 2010

coastie I had the same worry and have opened a few up with a small flat screwdriver, they allways seem to be full of nice clean oil

I took the outer sheild off the counterbalancer bearing once and wished I hadn't later casue it got notchy within 20 hrs, the original one went 200 hrs with both seals on.

I don't know which way is best, never really had any go wrong.

bergbro · Jun 25, 2010

So how did you know the CB bearing got notchy in 20 hours... paranoir or found whilst looking for sumthing else?
Not an easy thing to check I wouldnt hav thort.

Coastie · Jun 25, 2010

That's exactly what I wanted to know Bushy.
I did a re-build about 300 hrs ago and after about 40 hrs I had an open bearing collapse (non-chain side).
I replaced both with opens and I've got it all apart again and they came out fine this time. So that's about 250 ish hours and not the reason it's apart. So I don't know if the 40 hr collapse was lack of lube, bit of crap or just a dodgy bearing. This all sorta happened before I found out that they run shielded in the later models.

BTW - In the first rebuild (300 hrs ago) I also took 1 of the shields (crankcase side) off the counter balancer shaft bearing. It was also fine when it came out. I was also pondering doing that again but if you reckon they get enough lube with the shields in then that's how I'll go.
I mean - who am I to question the engineers?

bushmechanic · Jun 25, 2010

BERGBRO said:
So how did you know the CB bearing got notchy in 20 hours... paranoir or found whilst looking for sumthing else?
Not an easy thing to check I wouldnt hav thort.

lets see. gearbox broke couple times, main bearings floating, and the 105mm piston build plenty teardowns, im finished with my suspension so i gotta to something....

coastie as I see it an engineer only knows what hes doing at the time he makes the descision, someone with the benefit of hindsight is far more sensible than any engineer. (i should know, usually ive got hindsight and a degree, hindsight is more useful

) the amount of crap that can float around in there is why the seals should stay in. Obviously it doesn't allways float around in there but only one bit of crap from a gear dog would be enough.

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Cam bearing shields

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