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RE: Cam chain failure

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  • mclbiker
    My cam chain jumped the sprockets at 50k, upon stripping down, spring was weak but primary cause was the head on the floating guide had broken up resulting in
    Message 1 of 13 , Oct 4, 2013
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      My cam chain jumped the sprockets at 50k, upon stripping down, spring was weak but primary cause was the head on the floating guide had broken up resulting in the plunger going inside & loosing all tension. Prior to this bike has been maintained as per the manufactures workshop manual. Which says absolutely nothing about checking or maintenance. Triumph not even interested in looking at broken part.

      Cost £900 for parts for me to replace all bent valves etc on  bike not worth much more.  

      ---In triumphtrophy@yahoogroups.com, <adeux60@...> wrote:

       Gordon Smith has a theory she has done 100k more. Personally I wouldn't be surprised. I can  add another thought for the failure - how about low and erratic tickover or persistent misfire. As she was nick named Scary Mary by Gordon as she can sure rattle. Mind you I have done the head gasket since.

      You got it (sorry about my explanations) the ratchet won't reverse up and won't go further if the spring is out. But as soon as the tensioner is out you have to worry about losing a tooth at the bottom in particular - so a cable tie through the timing cover  might give you peace of mind. I think Haynes says something about a piece of wood but that puzzled me.

      --- In triumphtrophy@yahoogroups.com, <dieseldude1@...> wrote:

      Interesting, I wonder what caused the guide to break up? Lack of lubrication, chain slap, damage due to high revs. Certainly not much mileage on the old gal. As for the tensioner, if I just remove the entire unit. I'm assuming it will instantly ratchet all the way foward with the spring installed. So if I gently remove the spring and then the entire unit. Will it remain in position on the ratchet mechanism? Or will it reduce in length from the chain relaxing once the spring is removed during the removal process. Sheesh, guess I'll dig out the repair manuals and actually study this prior to diving in.


      On Sep 22, 2013 4:15 PM, <adeux60@...> wrote:

      mine has 30k on it and the already replaced guides (via PO) do not seem to have any wear on them. (although I found broken remains of them in quite a few places.

      I was talking about disasembling the tensioner and trying to ascertain its position but as it is under spring tension it just pops apart before you can hold it and say count the clicks.

      However if you take the spring out the back (centre bolt) and then slowly retract the entire unit (two small bolts)without disturbing it you may get a feel for its relative position.

      I have a spare cam chain and would like to know how to test it for stretch, 

      Of the previous broken guide (tensioner side) the biggest remain I found included a fracture near the fixing bolt at the bottom as I found the bottom inch wandering around in the cover (good job PO)  


      --- In triumphtrophy@yahoogroups.com, <dieseldude1@...> wrote:

      Hey Adeux,

      By sprung apart, do you mean the chain side spring retaining housing broke apart? Did it break from direct contact wear or just the spring tension over time? What condition was the guide in?


      On Sep 19, 2013 2:24 PM, <adeux60@...> wrote:

      Sorry samuel - not worth the risk in my opinion - i just would not feel confident about it.

      When I took mine apart the first time - I wanted to check the ratchet position but it all sprung apart before I could do so 

      but I havent tried what you suggest and probably you are right to tie down the lower sprocket as it can easily be a tooth out

      --- In triumphtrophy@yahoogroups.com, <dieseldude1@...> wrote:

      I'm expecting a new spring from England in the post today. And I'm  quite interested in inspecting the ratchet position. Nevertheless, here's my plan of action along with the usual disclaimer.... This method may or may not produce the desired results. So, I can't recommend this method since I've never successfully applied it. I suspect it should work on all but the worst cases of chain wear. Anyway, my thought is to pull the side cover and clinch a ty wrap around the chain. Which hopefully will remove enough slack to allow safe removal/installation of the tensioner. Does this sound like a feasible method? Or should I just delay till I can open the top and do the valves as well.

      96 BBBB PB
      New Orleans

      On Sep 19, 2013 10:06 AM, <gandrews2@...> wrote:

      Hi Miles,

      You are right, you've got to show these bikes the love, or at least ride it on a regular basis.

      I think a couple of things are going on based on your description.

      The stutter is a clogged pilot jet, or old coils. Your bike is almost 20 years old. 

      Surely you have replaced the coils my now. 

      The missing at full bore acceleration at 5000 rpm is either coils, or one of the cams are out of timing.

      I did some valve shim replacing on my Green bike after a big trip. I screwed up and the intake cam was off by one tooth, or the cam chain moved on the intake cam. The bike ran okay but didn't want to go over 100mph. I ran it this way for 9 months cussing the carbs, thinking it was a carb problem.

      Back to your bike.

      You can check the cam chain by see how many teeth are left on the tensioner's plunger/ratchet mechanism. If its in the middle, okay. If it's close to all the way out, two things could be worn out, the chain or the cam chain tensioner blade. 

      My brother changed the cam chain on his '95 Trophy at 110,000 miles and it was worn out. He gave the bike to me and I changed out the cam chain again at 210,000 miles. I gave the bike back to him and it now has 250,000 miles, but quite a few engine parts were swapped out at 229,000 miles.

      I changed the cam chain on my '96 Trophy (Green bike) at 70,000 miles and there wasn't much difference between the old and the new. 

      Okay, How to do it. There is a big bolt head in the middle and two little bolts, one on each side of the tensioner.

      First take off the big bolt, this will release the tension on the spring. Then take off the two smaller bolts and take out the tensioner. Now you can see where the plunger/ratchet mechanism is.

      The problem doing this job is there is a good chance the cam chain will jump a tooth since there is no tension on the chain. I would do this job with the valve cover off. I bought some plastic shims from the hardware store and I put one between the cam chain sprocket and the head case on each side. This shim keeps the cam chain against the sprocket and won't let the chain jump a tooth.

      Let us know what the problem turned out to be. I'm guessing pilot jets and the intake cam is off my one tooth.

      Good luck,

      Greg Andrews

      '96 900 BRG

      '98 Sprint Sport

      --- In triumphtrophy@yahoogroups.com, <miles.a.french@...> wrote:

      It's a bit late to reply to Greg, so I'm just going to hijack his post. My bike has started missing at full-bore acceleration in 5th or 6th at 5000/6000 rpm (poor old dear) and as I haven't done any maintenance for a while I thought I had better show her I Iove her. Besides checking the sparks and ignition (and the carbs for the pilot-jet stutter I've been living with) it's about time I checked the shims. While I'm in there I should check the cam chain. The PO won't have done anything about it, and she has 55000 miles on the clock, like Greg's brother, or at least his bike. How do I check the chain? Should I split it, get it out and measure it? Or should I just replace it along with the tensioner spring. The chain seems to be about £60 so I don't want to replace it unless I need to.

      Wotcher reckon?

      Thank you all for your help.


      BBSS (900 Mk1) '94

      --- In TriumphTrophy@yahoogroups.com, <triumphtrophy@yahoogroups.com> wrote:

      My brother's Super III just had a cam chain failure. His bike has 55,000 miles. He checked the valve clearances at 50,000 miles and no shim changes were necessary. The adjuster was about half way on the available ratchet teeth. On a 300 mile trip to San Francisco he made a stop at a motocross track on the way. He continued the trip going slowing, following at truck up a hill. The Super III lost power and then wouldn't run. He got a lift to my older brother's home. As he got into the valve cover he found the cam chain adjuster all the way out with the chain still loose, and the intake cam was 4 teeth off. How could the chain fail so quickly? Has anybody had a similar experience? He has replace the cam chain and that old chain has really been stretched out. The bike is running again and doing fine.
      Thanks for your assistance,
      Greg Andrews
      '96 900 BRG
      93,000 smiles

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