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XR 400 Head Removal

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Just checking. I'm going to remove my head for the first time to check things out and clean it. Anything I need to be careful of, or watch for?

Thanks,

Lightning

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Do you mean the head cover or the cylinder head assembly?

If the head "cover", be careful of losing the 2 dowel pins. Sometimes they stay in the head, sometimes they stay in the cover as you pull it off and can fall out. There's a picture on page 7-25 of the manual.

Other than that, just have some rags handy to catch any residual oil in the area. It's not much, but enough to make a mess if you let it get all over the head fins.

And make sure you DO NOT turn the engine over with it off, with the kickstarter or otherwise. Set the engine up like you were going to check the valves, before removing the cover. That way you can see what things look like with it in that position, like how well the cam marks align with the head surface.

And how well the auto cam chain tensioner is doing its job at keeping chain slack out.

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You have nothing holding down the cam. When you go to turn the engine over, the cam chain can dislodge the cam out of it's seat and the chain can jump time with the cam. Then you have that to fix.

Question. Why not turn it over with the head off?

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Do you have to replace the gasket when you remove the head cover?

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Do you have to replace the gasket when you remove the head cover?

If it comes off without kinking it at all you can coat it with a thin layer of RTV and it will be fine.

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If it comes off without kinking it at all you can coat it with a thin layer of RTV and it will be fine.

I don't recommend anything on the steel gasket. It already has a thin black coating. A thin coat of spray paint is .001". RTV is thicker. The gasket is .010" and this sets the cam bearings in the cam journals. Anything you put on that steel gasket will make the journals taller and the bearings will have a sloppy fit. Worse yet, is an aftermarket gasket that compresses to less than .010". This clamps down on the bearing races and causes all kinds of problems.

My bike came with an aftermarket gasket that was three thousandths too thin which was clamping the ball bearings tight against the cam. The cam did not spin freely with the rocker cover on. Luckily the PO was never able to get it started that way. I checked the journals with plastigage with a new steel gasket installed. The bearings had .001' clearance between the journal and race and the center journal had .003-.006" to the cam.

I would bet that many of these gaskets are mucked up.

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Interesting points BR, thanks for that view. My old xr250 ( 85 ) may have been having problems due to home-made tappet cover gaskets.

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