spinning my cam chain tensioner

[jimhickcox]

I just hopped on my 550/673 and it was making a crazy noise on fast deceleration. I poked around for a minute and it turns out it's the tensioner spinning up and down. My first thought was that it was some kind of catastrophic cam chain issue, but after thinking about it for a while, I suspect it might just be the tensioner. I shot a tiny video. Ignore the fuel dripping from carb one, it does that if I don't ride it for a couple of weeks: https://photos.app.goo.gl/3kBz56btFH3s2JRi6 (let me know if that link doesn't work).

I'm hoping this is just a case of needing to rebuild the tensioner (as per https://www.bwringer.com/gs/camchaintens.html). Does that seem right? Is it some kind of fried spring? Or is it less than that? Could it just be that the lock nut came loose? Do y'all put loctite on them? I've taken it off a few times and never had an issue until now, though it's only been ~50 miles since I replaced the top end so maybe I put it on dumb when I did that? When I have more time, hopefully this weekend, I'll take it off, pull the cover, make sure I'm still timed right, and put it back. Maybe that'll be enough.

 

[Maddevill]

Yeah your lock screw is loose. The part turning indicates that the rod is moving. Reset the lock screw and lock nut.
You're lucky it hasn't jumped cam timing.

Mad

 

[bwringer]

Bear in mind that the lock screw should NOT be tight; tighten till it touches, then back out half a turn and lock it there. The pushrod must be free to move back and forth, but constrained by the flat part of the pushrod.

It's also important that the spring on the cap nut be preloaded in the right direction. It's very light spring tension, but it's crucial to have a little tension. Perhaps this spring is broken or installed incorrectly.

Another common issue is dents on the ramped part of the pushrod where the hardened ball on the adjuster shaft presses. This can make the adjuster "jumpy" or "sticky". I've ground or sanded these flat. New pushrods do not seem to be available for the GS850, but I don't know about other models.



I'd take it out, take a look, and reset it per my instructions.

 

[jimhickcox]

Thank you both.
I pulled it off today and went through the rebuild document, though I don't have new seals or anything, so I didn't pull it totally apart. I familiarized myself with the bits and their jobs, and then reinstalled as per bwringer's instructions.

I made sure I put a little extra spit into getting my lock nut on there, started the bike, and it's still doing it. The spring on the cap nut seem to be correct – I have to turn the knob out the same way it says in the instructions to get the pushrod in, and it pops back on its own. I tried a few different settings with lock screw: backed out anywhere from 1/8 to 5/8 it acts the same. If I tighten it all the way the cap doesn't spin, but then I reckon I'm forcing it to act as a manual tensioner and it's not made for that (or probably set correctly for it).

The pushrod didn't appear to my eyes or finger to be dented or dinged up. Surely there's some amount of play intrinsic to the auto tensioner, right? If you watch the grime on the cap you can see it's rotating about 1/4 turn. How much should it move? I've never thought to look before because I never noticed it making noises, so definitely something different is happening. Does anyone have a reference from one that's working correctly?

 

[jimhickcox]

Sorry, I'm dumb, I can get a reference. My 750 is sitting two feet away from this bike.
Here's that tensioner if I rev and drop it. It barely twitches. Is that what it should be doing?
https://photos.app.goo.gl/B5vTQZaaTgJgUJNJ8

 

[jimhickcox]

Does that mean the pushrod spring is too weak?

 

[Redman]

Okay, I will ignore the dripping gas.
Should we also ignore that have no wiring on the oil pressure switch.....?

 

[jimhickcox]

Should we also ignore that have no wiring on the oil pressure switch.....?

Ha, yes, please. The clip that holds it in place broke about a week ago. I've been meaning to stick an alligator clip or something on the wire until I figure out a more permanent solution.

 

[jimhickcox]

If anyone reading this in the future is jonesing for an update: I got all the pieces in and did the rebuild as specified and it seems totally fine now.
Also threw an alligator clip on the oil pressure wire.
Also the carbs aren't leaking.

 

[rphillips]

I like folks making progress...Congrats.

 

[jimhickcox]

Thanks!
Progress is one of my favorite things to make.

 

[bwringer]

*snifff* I just love a happy ending!