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metisse

xr600r cam question

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I am putting a new (stock) cam in my '92 xr600r after losing the original cam and four followers to what looks like a lack of oil in the head.

I have checked all the lines, passages, screens and filter and am putting a brand new pump in. I did not find any obvious problems so maybe it was just low on oil at some point.

My question is the centre plain bearing. The head is scored in the centre bearing area and the clearance, with plasti guage, is .006" on the bottom and .005" in the top cover.

This seems excessive to me? Does anyone know what it should be?

Can I, or should I, plug the oil hole in the centre journal of the cam? I am concerned that with the clearance, excess oil flow out the centre may starve the followers and cam lobes?

It seems a bad bit of engineering to have two ball bearings with a plain bearing in the middle. Does the cam shaft flex that much that it needs a third bearing?

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Q::My question is the centre plain bearing. The head is scored in the centre bearing area and the clearance, with plasti guage, is .006" on the bottom and .005" in the top cover.

This seems excessive to me? Does anyone know what it should be?

A::Manual says..Check camshaft runout with a dial indicator..Actual runout is half of the indicator reading,,Service Limit..0.04mm or 0.002in

Q::Can I, or should I, plug the oil hole in the centre journal of the cam? I am concerned that with the clearance, excess oil flow out the centre may starve the followers and cam lobes?

A::This I don't know other than to say no one has plugged the one in my 86 XR600.

Q::It seems a bad bit of engineering to have two ball bearings with a plain bearing in the middle. Does the cam shaft flex that much that it needs a third bearing?

A::The feeling in this part of the world is their is no need to be concerned about the center cam to head meeting.Mine was fairly flogged and beyond it's service limit.The mechanic I deal with said it's not a problem and even the Machinist who did some work on the head did nothing about it..

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Thanks for your input Horri - It is on my list to get down there to ride - Sister in law is from Timaru area.

The cam is brand new so the run out should not be an issue but I will dial it and the old one just to know

How long have you run since the work was done on your head?

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Timaru aye..Bit nippy in winter for me but would suit you Canadians.

To be honest since the rebore/ valve train work/gearbox job I have probably only run the 600 for about 400kms just to make sure everything was ok..If it was going to seize or anything it'd have happened by now.

Also I will add this..The machinist did try and fill that hole..When my mechanic guy saw it he said whats this and unplugged it..I know who I'd trust and it's the mechanic as he has done a lot of work on these engines..We tend to keep old stuff running a lot longer down here than other Western countries..Price of new and all that.

Best take the head to a Honda mechanic and get another opinion if you want.

I'll just add that I have just phoned my mechanic Mike and he is adamant that the central hole beneath the cam to head center point should not be blocked..all sorts of things to do with pressure and the cooling of that area due to oil flow..No flow you get a swelling of that point and consequently pressure is put on the cam..Slightly over my head but I got his drift. I'll leave it to you to decide.

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metisse,

Stock, these things didn't have a plain center bearing. :thumbsup: XR's Only (or any good machine shop) can machine the head and cover to accept one and I suspect that's what's been done to yours. My 92 has a scored center journal as well. I don't have an answer for what the clearance should be, but your machinist should be able to give you a good suggestion. Or, call XR's only and see what they do.

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Thanks Eurorider

Mie looks a little more scored than that, and has what I think is excessive clearance. It looks like a bearing to me!

Good idea to try XR's though

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