1975 CT70 Cam Chain Q's

Discussion in 'Tech Area' started by Bidnadir, Nov 11, 2020.

  1. Bidnadir

    Bidnadir New Member

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    Hi Everyone,

    Working on a 1975 CT70 that I suspect has some valve issues and am planning on pulling the head, but as part of the prep for that process, I am considering also changing out the cam chain. The engine was making a lot of noise when running and adjusting the cam chain helped, but when I look at it with the stator off, I see that the cam chain adjustment arm is hitting the case. I also notice that the adjustment arm does not move when the jam bolt is tight, and I am not sure if that's correct or not. A video is worth a thousand words, so please have a quick look and let me know what you think. Really appreciate your help with this.

    https://photos.app.goo.gl/pYdMVDodKFHfagN18
     
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  3. Gary

    Gary Well-Known Member

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    None of mine have the newer adjustable chains but what I can say was that my 70 had around 2K on it when I got it - was adult ridden and not abused. Cam chain was noisy and sounded like it was slapping. Laid it on it's side and changed out what I could to buy me some time before I completely pulled it down. Well worth the effort.
     
  4. OLD CT

    OLD CT Well-Known Member

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    Pretty much every part of the timing set that I can see is in need of changing. The most important thing is to buy original Honda parts. I would buy all the parts from a vendor like dratv because it will be easy to see and order all of the parts required to do the job. Do stay away from aftermarket, so called complete sets. The tunnel roller is hidden in the cylinder and I would say it's old brittle and worn too!
    Cam sprocket in the head, tunnel roller that is in the cylinder, ''aka'' cam chain guide roller, D.I.D. chain, oil pump sprocket, tensioner roller, and even the little rubber tip on the tensioner.
     
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  5. farm dog

    farm dog Member

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    Came across same problem cam chain roller was a cheap one , would move back and forth. Rotate the flywheel and watch.
     
  6. lukelaw1

    lukelaw1 Active Member

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    You also need to back off that screw. The jam nut only keeps the screw tight. You should also remove the plug on the bottom of the motor that remove the tensioner. Confirm that the springs are there and not missing or broke.
     
  7. Gary

    Gary Well-Known Member

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    Duh... old fart didn't realize that was a video :confused:,didn't see how worn that oil pump sprocket was
     
  8. Bidnadir

    Bidnadir New Member

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    Hi Guys,

    Thanks very much for the advice! I'll order new OEM Honda timing chain, rollers, etc. and give 'er a go. Changing out the pump sprocket is the part that concerns me. The rest of the job I think I can handle. I'll see what I can do. Thanks Again!
     
  9. Beretta

    Beretta Member

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    I'm new on here too ! I've learned a bunch since my 1st acquisition in March--Thanks to the Guy's on here.
    The 1st thing I do is a Compression Test to determine the condition of the Engine and proceed from there, 2nd is I always Rebuild the Carburetor among a few other Items on my Check list. I now have 4 H's and they all have slight differences in performance-- 2 of the 4 will easily hit 45 and the other 2 hoover @ 40-- Fast enough for me !
     
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  10. lukelaw1

    lukelaw1 Active Member

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    yeah i didnt watch the video either.
     
  11. Rob Kammer

    Rob Kammer New Member

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    I'm just getting into a rebuild of a friends CT 70. How many miles are on your bike that you're having chain issues with? The bike Im working on has less than 1000 and I'm hoping there isn't much that's really worn.
    Rob
     
  12. Beretta

    Beretta Member

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    Seems at lest to me the Timing Chains get loose at 2 to 3000 miles or so.
     
  13. Rob Kammer

    Rob Kammer New Member

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    Rob here. Thanks for the info. Had the motor back together for a run test and it runs and idles nicely. All three gears work, at least on the test stand. I took the motor back out to have a helicoil installed, put it all together, cleaned and painted it all together and put it back on. I had sprayed the cam sprocket cover earlier and the masking tape I put on the motor for the final painting got messed up so I took it off and repainted it. That's when I notice the cam chain seems to be really loose. This model 70 does not seem to have any way to adjust the chain tension, only a spring in the tensioner tube. This spring is NLA through Honda. I doubt the chain has stretched this much with less than 1000 miles on it.
    Am I missing something on the tensioner? Does the tension increase with oil pressure.
    Open to suggestions.
    I have not filled it up with oil yet am have ordered a flywheel puller cause I didn't think the Cushman method was a good idea more than once. Cushman method= loosen the nut and whack the shaft with a hammer. Cushmans are all iron construction.
     
  14. lukelaw1

    lukelaw1 Active Member

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    Yeah dont hit with a hammer. What is the motor serial number? This will help identify Cam Chain tensioner.
     
  15. Rob Kammer

    Rob Kammer New Member

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    Hi, I don't have an engine # but the bikes number is 143913. I pulled the stator today and found that the tensioner arm was maxed out against the engine case and the chain is still quite loose. Is it possible to remove a link from the chain? I will probably remove the sprocket and chain tomorrow, hoping that I can get it back together without taking the head off again.
     
  16. Bidnadir

    Bidnadir New Member

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    Hi, mine had exactly the same issue with the tensioner arm maxed out, hitting the engine case. I took the advice of the guys on here and purchased a new chain and tensioners, along with a new cam chain sprocket, and that totally resolved the issue. I don't believe you would be able to take one link out of your existing chain, but I'll defer to those on this site that are more knowledgeable. I think if you try that you'll find that you can't get the chain back on. Even though it may seem extremely loose now, it's probably stretched much less than one chain link.
     
  17. Gary

    Gary Well-Known Member

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    Don't,if its that worn it's time to change it. Head does not need to be removed. Every thing is accessable with the engine together with the exception of the crank gear,but you might have to pull the right cover and oil pump if you want to change the oil pump drive gear. Just lay the bike on it's right side when you go to change anything.
     
  18. cjpayne

    cjpayne Well-Known Member

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    Its possible to change out that T chain without removing the head. Its kinda tricky though. Also, there is no master link in that chain and even if you got one removed and put back together, I'm pretty sure it would throw the timing off.
     
  19. Tripod

    Tripod Active Member

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    Why cheap out on a worn out timing chain? Replace the whole assembly as a unit instead of risking a valve and piston becoming friends.
     
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  20. kirrbby

    kirrbby Well-Known Member

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    Remove the cam sprocket out thru the cam sprocket cover hole. Then pull the cam chain idler wheel...that's in the cylinder... thru that same hole. Then remove the stator plate and remove the rest from there. Put it back together the same way.

    So you don't have to remove the head.

    Buy new parts...it's the only right way. Your cam chain has stretched a mile...toss it. There IS someone making a cam chain master link. If you get one you could maybe use it to make a nice bracelet for wifey :)
     
  21. Gary

    Gary Well-Known Member

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    Or tire chains.... 100_0677.JPG
     
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