adjusting the cam chain tensioner correctly ?

[spitfire]

hi,
i have been trying to adjust the cam chain properly with your help but have run into a slight problem and need more advice.

i have lined up the T mark with the rotor to find TDC and then adjusted the tensioner plunger with the outer adjuster bolt until its flush.

then i rotated the engine to check the setting but just before it rotated 360 back to the T mark on the rotor the tensioner plunger made a clicking sound and popped out 3mm, then i turned it a little further so the T was aligned and it retracted and was flush again.

so my question is where should i have done the adjustment from ? from the T mark where i think TDC is or from a little before that where it popped out. because as the way i have done it, the plunger does pop out 3mm when i rotate the engine. hope this makes sense.

would like to get this right before i inadvertantly break something

 

[5twins]

Yamaha gives no exact spot, like the "T" mark, at which to set the adjustment. They simply tell you to rotate the engine by hand and watch for the plunger to pop out past the adjuster screw. If it does, you're supposed to adjust it flush with the screw again. Unfortunately, with just about every turn of the motor, the plunger can pop out past the adjuster again. You end up loosening and loosening and loosening the adjuster, eventually ending up with the chain way too loose. Then it rattles like loose valves when you start the bike.

An easier and near fool-proof method for setting the chain tension is to do so while the bike is idling. Set the adjuster screw so the plunger bounces in and out maybe a MM or 2 without coming out past the end of the screw. If the plunger stops moving, you've set it too tight.

 

[spitfire]

many thanks 5twins for your clear explanation. i feel more confident now and will try this method instead

 

[xjwmx]

It seems to tighten a great deal as the engine warms up, as evidenced by movement disappearing. So you want to check that there's still movement when the engine is hot, too. In the manual the method isn't clear, then in a revision it still isn't clear. Worst part of the manual.

 

[spitfire]

turns out i cant adjust the tensioner when the bike is idling because the screw wants to unscrew itself and there is no way (atleast on my bike) of locking it in place. i can only lock it tight when i screw the outer acorn shaped nut in place. i also tried to unscrew the bolt until the inner plunger pin didnt go past the adjuster screw. did that and started the bike but the rattle was much worse. so i have just done it by eye and i'll see how it goes

 

[5twins]

Have you checked the tensioner assembly to see if the copper damper washer is there? If it's missing, the plunger will come out past the screw end when tension is correct.

 

[anysnail]

it almost sounds like you aren't loosening or may be missing the lock nut. it's about the same size as that acorn nut you are talking about but it mounts between the acorn nut and the engine block.

imagine there is a picture here that would show you what i am talking about. this forum won't let me upload right now.

 

[anysnail]

HA! here you go dude. do you have this nut?

 

[5twins]

Several years had no lock nut ('76-most '79s).

 

[anysnail]

oh. fuck. my bad

 

[spitfire]

thanks guys for the picture and your suggestions.

my bike doesnt have that narrow nut, only the big one. but its a 79 SF, so thats probably the reason (havnt worked out how to put my bike details on the bottom of my posts yet). so if some bikes never had that narrow lock nut what did they use instead ?

i will take the whole assembly out and check to see if the brass washer is there. is it just a simple matter of undoing the 6 bolts around it. does any oil come out when i pull out the assembly as i have noticed some oil had collected in the big acorn nut and a little was coming out of the end of the plunger.

 

[5twins]

You can leave the housing in place. Just unscrew the adjuster screw all the way until it comes out. Withdraw the plunger and spring with it. On those models without a lock nut, the cap was the lock nut. Once tight, it held the adjuster at it's setting. I've always wondered about that set-up though. What's to stop the cap from turning the adjuster screw tighter as you tighten it down, throwing off your adjustment? That may be why earlier models had the lock nut and later models went back to using one.

 

[XSLeo]

I might suggest getting a later model adjuster, complete with housing. Swap it for yours.
I like to set the tension with the engine warmed up and at an idle. Adjust so the inner rod moves in and out about 1-2 mm's. The rod should come out to flush and no further.
If the rod is not moving, you have the adjuster to tight. If the rod don't come out flush you have it to loose.

 

[spitfire]

i took out the adjuster screw and found the copper washer. dont really know where to go from here though. i read a post about using a plastic washer instead, would that help.

like the idea of replacing the whole thing for a later one with lock nut. good idea. i will keep my eye on ebay for one.

 

[anysnail]

i don't know if you have craigslist in the UK but i have an XS650 friend here in ohio that sold a whole busted motor for $20. the thing was basically useless but for what you got goin on it seems like just the thing.

so yeah. check craigslist. every day. hourly.

 

[johnnymac]

Spitfire- My set-up is different (1975 xs650b). But I tried setting the tensioner while running and when it appeared to be correctly adjusted- it made more noise. I ended up pulling the plugs and shifted the bike into its highest gear, then rotated the rear tire- It was easier for me to adjust it this way- I just felt I had a little more control and when I was done- No more rattle-

 

[kent_in_kc]

I'm about to set the cam chain on my '76 but you guys have me worried. The bike runs pretty good now, like a sleeping dog. Should I let it lie?

And why can't sleeping dogs ever tell the truth?

 

[anysnail]

shoot, kent, don't be worried. i adjusted mine in five minutes and it runs a whole lot quieter now. of course mine has a locknut.

 

[spitfire]

i think each time i go out on it i will just tighten it up half a turn and see how it runs, although always keeping in mind "its better to hear it than to smell it" which i read recently here

 

[Stone]

to avoid starting another thread I thought I would just go with this one...I too am a weee bit worried about doing this although mine vibrates like hell around 60.

but if i understand it correctly I can do this while the bike is running? and stop adjusting the rod when it starts running better or what?

any help would be frickin sweet