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Cam chain guide...worth replacing?

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  • Cam chain guide...worth replacing?

    I have a 1989 Kat 750 with ~70,000 km on the clock. When I was replacing the cams with some GSXR cams last spring I noticed that the cam chain guide (the one that the tensioner presses on to tension the chain) is looking quite anemic. The plastic is understandably old and is quite brittle, and it looks like a small piece at the top already broke off (I found most of it in the tensioner hole when I pulled it out.) However, upon reading the service manual, it seems like a royal pain in the arse to change it (remove engine, split the case, remove the head, remove the pistons and crank, remove the chain, then finally do the 5 minute job that you did all that work to do.)

    I haven't been able to find many threads on here of people actually changing these things, unless I have been looking in the wrong place.

    So the long and the short of it is, is it worth my time replacing this on a bike of this age and mileage, or do I just ride it till it dies? On the ride till it dies front, what is the worst that would happen to the engine if that plastic piece completely disintegrates? Tensioner presses directly on the chain making a hell of a racket until I pull over and shut it down cause its fubarred? What would be damaged besides perhaps the chain? Would the cams be saveable? Are these engines interference engines? I realize that oil starvation could also be an issue if pieces of the plastic start breaking off and clogging the pickup.

    Another factor to consider is that I have a second 1997 Kat 750 with ~40,000 km on it, so I wouldn't be that broken hearted if the engine grenades itself, providing it doesn't cause me to crash when it does so and my possible ability to still use the GSXR cams in this other bike.

  • #2
    If the can chain goes, engineer is toast. You'll have pistons hitting valves, rocker arms breaking, and I would imagine damage to the cams. I personally would not trust them unless a qualified mechanic gives them an ok.
    I've had an engine grenade before, I had damage on my cams. I would not personally re-use them.
    1998 Katana 750
    1992 Katana 1100
    2006 Ninja 250

    2006 Katana 600 RIP - 130k miles


    • #3
      If I do go the route of replacing the guide, are there any tips an tricks to save time/effort, or is it pretty much follow the manual to the T?

      Although, looking at the other consumables I will have to replace in the process (gaskets, orings, etc.), it is becoming less and less appealing.


      • #4
        My thoughts would be...

        Is this something I wanna do. Will I enjoy it just for the task or learning experience. Will doing this give me satisfaction.

        If no is the answer to any of those, I would not...

        If you choose not to do it, then ride it till it dies. Replacement engines are still widely available and very inexpensive. Swapping a motor is relatively easy, and quick to do with some basic pointers and steps.

        93 750 Kat

        Modified Swingarm, 5.5 GSXR Rear with 180/55 and 520 Chain, 750 to 600 Tail conversion, more to come. Long Term Project build thread

        "I've done this a thousand times before. What could possibly go wron.... Ooops!"


        • #5
          Ya, I am not really looking forward to doing the work as I don't really have a place of my own to do it.

          If I ride it till it dies, could the failure be catastrophic enough to cause a crash?

          I was thinking of just swapping the engine from my second bike as it runs as well in order to preserve at least the cams in this one until I have a place of my own to do the work. Are these pointers and steps you speak of located in forums here? As in I should probably search for them?


          • #6
            My thoughts would be park it at the first opportunity and swap the other pre motor in.

            It's worth more now not completely broken DOT heads are still in good demand also.

            Like Krey said it would have to be something your really keen to do and have time / money / space to do it, rebuilding my motor the parts alone cost a fair bit as I had a couple of bearings to replace et al seals gaskets, also think the tools you need to do the job

            If you were lucky it would just make a hell of a racket but create a lot of internal wear on the cam chain tunnel.
            Worst case would probably be a seized motor if the Chain breaks depends if / where that could happen.
            “Anything that happens, happens. Anything that, in happening, causes something else to happen, causes something else to happen.
            Anything that, in happening, causes itself to happen again, happens again. It doesn’t necessarily do it in chronological order, though.”
            ― Douglas Adams