Cam chain gap on sprocket

[steve68steve]

Thanks for all the replies, and sorry about hi-jacking. I honestly thought it would be a one post issue and might do Zepfan a service.


I'll keep at it and reply back to here. Will be traveling and holidaying for a while so if I go quiet, it's not lack of appreciation, just lack of time.


I've been thru the thread about the CCT being getting chewed up by direct chain contact. That's definitely not my issue. It's all apart and on the bench, so I'll just keep fighting it.

 

[Crew Chief]

If the timing marks align exactly after being rotated, the chain is not stretched. My DRZ for instance is 2 to 3 degrees off. It will get a new chain when I do the top end on it. You can also use a dial indicator to measure the distance between a specific number of pins in different places. I'd be surprised if you find a significant difference, but damage to an individual pin or two is possible I suppose.

 

[Nikolajsen]

[font=verdana, arial, helvetica, sans-serif]Bottom line, it's getting a new chain. Hopefully the last hi-jack here will be: "yep, new chain, all's well."[/font]

I don't think this is a bad idea..
I have never seen a chain in god condition, do this on the sprocket, even when it is much too tight (or CCT engaged)
So I look forward to your last comment "yep, new chain, all's well"

 

[SilverBullet]

...So I look forward to your last comment "yep, new chain, all's well"

As many others stated, very doubtful the chain is the culprit but Steve can always hope for a Christmas miracle.
Since a new chain is only $30 it doesn't hurt the pocket much.

_

 

[Don in Lodi]

Have you tried giving the chain a tap or three with a screw driver handle or something to see if it will settle in at all? If it settles easily then the tensioner isn't tight enough. Is the chain fully supported by the guides? I'd read once of a chain riding off the side of a guide at some point.

 

[Zepfan]

Sounds like I better order the chain also. I'm waiting on parts.

Weird!....... I can't imagine the chain looking like that (gaped). I put the sprocket on the chain and it meshes perfectly, no gap.

Good post Steve

What did you do with the bottom gasket?

How hard are the pistons to get back into cylinders when you n pull? Manual shows working the rings in by hand. I'm guessing it's tricky, maybe a 2 man job.
The cylinders can be moved many inches apart with cylinders still inside barrels. I thought to re-use greased gasket.

 

[Checkswrecks]

Sounds like I better order the chain also.

How hard are the pistons to get back into cylinders when you n pull? Manual shows working the rings in by hand. I'm guessing it's tricky, maybe a 2 man job.
The cylinders can be moved many inches apart with cylinders still inside barrels. I thought to re-use greased gasket.

It can't hurt to change the chain with how far you've come.


As for inserting the pistons, I started using simple hose clamps and plastic milk jug material when I couldn't find my nice ring compressor. I actually like using the clamps and plastic more at this point. Works like this and also works for sliding the cylinders over the tops of the pistons.
https://www.youtube.com/watch?v=VISqGGMcBTc

 

[steve68steve]

Since I started this as a hi-jack, I'll keep all the info together - another (hopefully second last) edit about the timing chain:

I tried the suggestion to release chain tension on the intake sprocket by cranking it forward a bit. The chain still didn't seat. I turned the engine thru some random amount and heard a "click" from the chain, so I brought it back to the timing marks, which were still perfect.

Perplexed, I turned the engine over a few more times and there's a point in the cycle at which the chain "clicks" on every revolution. At this point it does seem seated a little better. I pushed down on the section of chain which spans the two camshaft sprockets and it deflected a lot... like maybe 1/4 - 1/2". There is NO slack at the timing point.

Then I ran the engine around a slowly checking the tension on that top section of the chain and it varies a lot thru the cycle. Since the distance between the sprockets is fixed, I take this to mean that not only is the chain stretched (worn), it's not uniformly so. The "click" happens when the spot of low tension meets the intake sprocket - the chain settles deeper into the sprocket at that point - I assume this movement is what causes the sound. I wonder if this "click" once per revolution at 3000rpm is what I was hearing.


Bottom line, it's getting a new chain. Hopefully the last hi-jack here will be: "yep, new chain, all's well."

The part in bold above is obviously not true - it was a "senior moment" likely fueled by doing valves on my old DL1000 which had gear-driven cams. Everything that follows it WOULD be true, if it were true - but it's not. The post is an homage to my derptitude.


Update:


I jinked and jerked around with that timing chain, decided to buy another one, then read a bunch of stuff here about how long these chains are supposed to last and that mine couldn't possibly be worn out. Other member's photos confirmed my cam teeth looked OK, and the fact that the cam teeth and chain recesses are the same shape suggests nothing is worn / wearing.


I decided it's all much ado about nothing and just put it back together with the old chain. It runs and all seems / sounds well, altho I haven't actually ridden it yet (need to bleed clutch first).

POINT: I think my pictures are misleading. Having the engine out of the bike enabled looking straight in at the (backlit) teeth using magnification. It really makes it look bad - in fairness, I did get it a LITTLE better than the photos before putting it back together. If you're expecting a perfect fit here, don't. The SM says to replace the cam sprockets and chain when the gap between the tooth and link is 1/4 of a tooth. That is a HUGE amount of play vs. the pics I posted.

There's every chance I'll have another - tragic - update here very soon, but right now it looks like I could have just went with "wrench more, worry less."

 

[mrpincher]

Steve68

Your post prompted me to pull out my photo's from the recent CCT switch and valve check I performed this fall on the 2012. My chain and sprocket gap is visually identical to yours. With both bikes having the same gap, I took that to mean both bikes were OK... because my bike has been running better than ever, except I can't start it right now. I guess the battery is low and it's too cold where the bike is stored + I don't feel like screwing with it. Is flooded and won't fire BTDT. My KTM, on the other hand, pops right off like it's time to go riding. Oh Yamaha, why.

 

[steve68steve]

Steve68

Your post prompted me to pull out my photo's from the recent CCT switch and valve check I performed this fall on the 2012. My chain and sprocket gap is visually identical to yours. With both bikes having the same gap, I took that to mean both bikes were OK... because my bike has been running better than ever, except I can't start it right now. I guess the battery is low and it's too cold where the bike is stored + I don't feel like screwing with it. Is flooded and won't fire BTDT. My KTM, on the other hand, pops right off like it's time to go riding. Oh Yamaha, why.

Thanks so much for taking the time to share this - it gives me a LOT of peace of mind. The reason I originally posted my pics is because it didn't look "normal" to me, but I didn't know what "normal" was supposed to look like.


20/20 hindsight: I bet if I took those pics at normal magnification, a few degrees off perpendicular to the sprocket face, many wouldn't have thought it looked wrong.


I ran it on the center stand until the fan came on to confirm everything works, and it did seem like it was running better than ever. Thanks again!

 

[mrpincher]

Zip ties are cheap so I zip tied my chain to both upper and the lower sprockets in four places, just to be sure the chain didn't jump teeth when I unloaded the CCT. I had to cut a scrap walnut stick to use as a lever by wedging it up/where the CCT guide rests against the chain tensioner. Releasing it took more than a gentle tap on the CCT like I had been led to believe. I cussed and levered on that stick until the CCT finally popped open. Then I brought over some mirrors and lights to see that the chain was still riding on the guide. When I got a visual confirmation that all looked good, the chain was tight, I started cutting zip ties, watching for the chain to load and try to jump on the sprockets. Nada. Everything stayed put. Spun the motor, checked for gasket leaks, buttoned it up and started it. Zoom, zoom. I've since put just under 700 miles on it. Since the new CCT, new clutch and valve check, the bike seems to be a bit gruntier as it accelerates. Have no idea why? I didn't need to change any valve shims. HOWEVER, I'm free of that frightening clatter at startup. New CCT probably saved my engine. Now its time for a new battery. Hope this makes sense and helps someone.

BTW - The point of all that text above is ...there was no way that chain could have risen on my sprockets because I had everything zip tied tightly in place. My photo's showed me that. My picture angle was a bit different than yours (steve68) - but the gap didn't appear substantially different.

 

[Nikolajsen]

So happy, to read your bike seems to be OK anyway ::012::
But I still don't understand why the chain/sprocket can do that.... ???
When the parts is OK, and correct timing.

 

[steve68steve]

So happy, to read your bike seems to be OK anyway ::012::
But I still don't understand why the chain/sprocket can do that.... ???
When the parts is OK, and correct timing.

That makes two of us.


When the intake cam lobes contact the buckets, it provides additional resistance to the sprocket being turned. The chain keeps pulling, so it gets tighter. Since the teeth are little inclined planes, the chain force can be divided into the portion pushing the the tooth forward (around), and a portion forcing the chain to climb up the tooth.
AFAICT, the only thing keeping the chain from popping off the tooth is the tension of the chain behind it, engaged with all the other teeth. Once THAT tension gets too low (because of slack), the "climb the teeth" force will be higher than the countering chain tension force and it jumps teeth.

 

[Checkswrecks]

Steve -
Thanks for updating this.