Type D cam chain adjustment

[DevonDel]

I was looking to make sure my cam chain tension was correct on my new to me 1978.

I've removed and identified the tensioner as a type D, and the manual says that it should be turned until the push rod is flush. Well there is no way that can happen as with the rod pushed into the max it's still short of the adjusters end?

How do I know the right tension with no guide?

 

[5twins]

You may have some mixing and (not so good) matching of parts going on here. There were no fewer than five different tensioner assemblies used on these motors over the years, and being 30+ years old, sometimes parts get swapped - and not always for the better .....

You'll want to start checking part sizes. Your type D plunger should be about 92mm long with about a 6mm "head". The "pin" portion should be about 62mm long .....

The adjuster screw should be about 61mm long overall, 55mm of thread with a 6mm tall hex on the end.

If you find some wrong parts and need to acquire replacements, I advise upgrading to the type E assembly. The type D was a bad design on Yamaha's part. It had no lock nut for the adjuster screw. If you look at all the other versions above, you'll see they did. Yamaha figured the acorn cap nut could act as a "lock" for the adjuster screw on the type D. Well, it can and does, but the problem is that when tightening it down, it may inadvertently change (tighten) your adjuster screw setting. Running the chain too tight can lead to premature stretching.

 

[DevonDel]

I've now reinstalled it without part 21 the small spacer.

This has had the effect of making the plunger more visible and I can tension it so I get a mm or so movement. Before it was wound to the max with no movement in the plunger.

 

[5twins]

That's the damper washer. You want that on there or the plunger may tick like loose valves. The best and easiest way to set the proper tension is while the engine is idling. Watch the plunger and set for 1 to 2mm in-out movement. No movement is too tight, more than the couple MM, too loose. Don't worry about whether the rod makes it out flush with the end of the adjuster screw. That won't happen on every one of these. Especially if you were to "upgrade" the copper damper washer to the newer rubber/metal one shown in the drawing above. It's thicker than the copper washer so won't allow the plunger to come out as far.

 

[DevonDel]

It is the 'upgraded' metal and rubber damper washer which is clearly the issue. It's so thick you can't see if your getting any movement, it moves the rod so far into the adjuster you can't see it.

 

[5twins]

Yes, I tried that washer and had the same problem, lol. Mike's sells it as an "upgrade" but doesn't mention the problem you're going to have using it. As I mentioned above, consider updating the tensioner to the later E type. Besides fixing the no-lock nut issue and it's possible bad side effects, it works better with that new style thicker damper washer. That's what the new washer was made for and where it comes from.

The upgrade is simple, all that needs changing is the plunger, and adding the lock nut w/ it's sealing washer. The adjusting screw, spring, housing, and acorn cap nut are the same on the two versions.

 

[DevonDel]

I've found an E tensioner on eBay for £20, thanks for the advice. It's running nice and quiet without the damper washer at the moment so I'll run it like that until the longer rod and lock nut arrive

 

[Oddjob]

Sorry for bringing this back from the dead... I have a D style tensioner on my project 78 bobber, but it looks like the previous owner gifted me a E style tensioner as part of his parts stash... However it's missing the damper, part 15 in the above picture posted by 5t...

Is there a significant difference in thickness between the old and new damper, does anyone foresee any issues with using the old style damper washer with a E style assembly...

 

[5twins]

There's only a 1mm difference in thickness between the old copper and new metal/rubber damper washers. Upon further research, I discovered there is an early and late version of the type E adjuster. You can read all about it here .....

http://www.xs650.com/threads/cam-chain-tensioners.1056/page-2

 

[Oddjob]

Thanks 5twins, that thread clarifies a lot... It would appear that I've got an early type E assembly...

Assuming that you've run both types, is there a difference in the damping effect of the solid copper washer vs the rubber coated?

 

[5twins]

None that I can see. I tried the later one because Mike's advertised it as an upgrade or improvement. I feel that's just a sales pitch. I saw no difference other than making it difficult to adjust. The copper washer from your type D will work fine on the early type E and is what it was designed to use. This soft damper washer is there mainly to stop noise. I don't think the head of the plunger slams into the back of the adjuster screw super hard, just hard enough to tick if there wasn't a soft, sound absorbing barrier between the two. I've never found a plunger or damper washer all mashed up or worn out.

 

[Oddjob]

Thanks 5twins...

So as a sanity check, when I assemble (on the bench) the plunger/washer/spring/screw I have to more or less completely compress the spring in order to bring the pin flush with the nut. In order to make the pin protrude past the nut I would have to bottom out the plunger/washer/screw, and it only seems to protrude by about 0.75mm or so... does this seem about right?

I've been reading about the two main methods for adjusting the cam chain... If I adjust using the static method of having the pin flush with nut, why would I expect to get a different result using the dynamic method of having it dither in/out by a mm, but still flush with nut on its outer most extension?

 

[5twins]

Yes, that sounds about right. You're dealing with the early 60mm long adjusting screw, correct? Even so, slight wear on all the parts could affect how far out the plunger will come. For instance, the copper damper washer may be pounded a little flatter than when it was new.

The static adjusting method can be very prone to errors. As you turn the motor over by hand, at some point during the revolution, you'll have valve springs pushing valves shut. That pushes the rocker which pushes on that cam lobe. This can cause a "snap" or "whip" of the chain. This whipping action will bounce the plunger way out momentarily. If you adjust the screw flush at that point, it will be too loose. Rotate again and this can happen again, so you re-adjust, rotate again, re-adjust, etc. Eventually you end up with the adjustment setting way, way too loose.

So, sure you can use the static method initially, just be aware of and know to disregard that occasional big bounce of the plunger. Then I recommend checking it while running. There's no way to screw that up. Turn the adjuster in until plunger movement stops or nearly stops, then back it out until you get the small amount of movement needed.

 

[Oddjob]

Yes, I've got the early type E assembly with the 60mm adjuster and 2mm thick washer (salvaged from the D assembly)...

I've been playing around with this for the last few days... Seems to be a tad noisy when I "think" I've adjusted it correctly... I believe that I've got a somewhat stretched cam chain, as evidenced by having to use all the slotting on the timing plate to get it to fire in the middle of the "F"...

Anyhow I think I'll keep trying as per the above... perhaps a bit of cam chain noise is to be expected if the chain is stretched...

 

[5twins]

That's another "plus" for the running adjustment method. You can hear the chain get noisy or the noise go away as you loosen and tighten the adjustment setting. Keep loosening the adjuster and eventually you'll hear the chain start to tick like loose valves. Tighten it back up and you'll hear the noise eventually go away.

Yes, sounds like your chain is getting pretty stretched out. Running out of timing plate adjustment is one of the signs of that, probably about the easiest to spot.