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Monday, April 9, 2012

Damn Cam Chain...

I haven't made the progress I'd hoped for on the XR250R. The next step is to install the cam and cam sprocket. Simple enough in most cases but I couldn't get the timing chain loose enough to allow the sprocket to sit on the cam properly. I messed with it until I ran out of ideas and finally called in some help from Seamus, since he is familiar with these engines. The problem I was having was that I couldn't release the pressure of the chain tensioner to gain the slack that I needed. Of course Seamus figured out the problem within about a minute, and together we mounted the sprocket, checked the timing and called it a day.

The next step reiterated that I double check the cam timing, so I did and discovered that we'd mounted the sprocket 1 tooth off of the correct setting. I took it back apart and tried to reproduce what he'd done with the tensioner to allow some slack in the chain, but I couldn't get it to do what he'd been able to. So I'm back to where I was.

Here's the cam in the head.

This is the top half of the head containing the valve rockers and finger followers.

A closer view of the rockers and finger followers. I guess the finger followers reduce the mechanical force required on the rocker shafts because of the steep valve angle.

Any questions?

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