CC adjust trick,, what the

[Crazcnuk]

There can't be any other reason for the C mark, since it doesn't relate to any particular position on the chain, and has nothing to do with the cc itself.

I suspect it was easier than saying 'rotate in the direction of the arrow for a bit'.

I have never read to rotate any more than it took to get to the c mark. (in the direction of the arrow.

By turning the crank you are just 'bunching' the chain at the cc side of the motor between the crank and cams.

[Welsh1100]

Cam Chain adjust

Ignoring the manual...I tried adjusting the tension using an "old school method. With the bike warmed up and idling..I loosened the tension lock nut. It is my understanding the tension bar is spring loaded and will "sit" it's self. Curious..I followed the manual's instructions and checked the timing mark. It seemed to be spot on. Cam chain noise went away and the bike seems to run fine thru the entire power train.

[skids]

Ignoring the manual...I tried adjusting the tension using an "old school method. With the bike warmed up and idling..I loosened the tension lock nut. It is my understanding the tension bar is spring loaded and will "sit" it's self. Curious..I followed the manual's instructions and checked the timing mark. It seemed to be spot on. Cam chain noise went away and the bike seems to run fine thru the entire power train.

I am too chicken to try that...

[jmnjrpa]

Old school???

That's a good way to jump timing. There is a reason for the tensioner not reversing (either auto or manual.). One hiccup from the engine during that "old school" method and your valves are bent! Not advisable!

[yamtom]

oh man

You are bold to do that old school method, I would never do that.

Got mine done by the book today, multiple turns of the crank clockwise from left side, then put on c mark, then do the release of tension and the retourqe of the bolt and locknut, put it back together, this time with new bolts and antiseize on the threads. Nice and quiet now.

Thanks guys.

[prometheus578]

Uhm... Welsh... far be it from me to tell anybody what to do, but... uhm... don't do that again.

As I was sitting here trying to figure out how to write in the greatest detail just why that is a bad idea... several other people posted. Let's just go with the simple and quick answer provided by Jmnjrpa.


Ahhh. the ol' "Why adjust the timing on the "C" mark question. We had that debate many years ago.. way back in 2005, I believe. first, let me point out something concerning the adjusting proceedure.

One turns the crank to the "C" mark and stops. This keeps the chain tight at the rear of the engine and places all slack at the front, where the adjuster can adjust it out.
If, when turning the crank... you go PAST the "C" mark, do not turn the crank the other way to bring it back into alignment. What you've done then is to put slack at the back of the engine and you will not be able to adjust that out.

OK... "Theory of the "C":

Several differing thoughts were brought forth... but I believe that RANDY hit it right on the head. It has to do with the cams and the position of the lobes. Lets do a run-through of the adjustment proceedure... but done incorrectly.

You've cranked around several times, but stopped the crank at a position OTHER than at "C". Ok, what do we have? The chain is slackless at the back of the engine... The chain is slackless at the bridge area between the two cam gears.... and all the slack is at the front where the adjuster can do it's job. (at least, we think so, as we can't really see the chain and what's goin' on in the cam area)

When we decided to stop the crank at a random position... this also placed the cams at a... shall I say, a random position. We now have cam lobes pressing down on valves, holding them open. Not a big deal, as that's what cam lobes are supposed to do with valves while an engine is running.

But, let's look at this from a non-running/adjusting the chain slack aspect. Now we have valve springs putting pressure up against the cam lobes... (which is fine... does that all night when the bike is sitting in the garage)

Here's how it screws up the chain adjustment. Let's say you have an open exhaust valve.
"You have an open exhaust valve."
(Sorry, bad joke)
Anyway... there was an exhaust valve starting to close. The lobe isn't directly pointing at the valve bucket but is at an angle to it... as it was leaving the bucket when we stopped turning the crank.

The pressure from the spring on the open valve pushes against this angled lobe on the exhaust cam. This pressure spins the lobe up out of the way as the valve tries to close. Of course, as this lobe is attached to the cam... and the cam is attached to the cam gear... and the cam gear drive the chain... this rotating action of the cam has now taken some of the "adjustable" slack from the front of the engine and placed slack in the bridge area between the two cam gears, where obviously it can't be adjusted out.

So... not to make a long story out of this... When the crank is placed at the "C" mark... the cam's lobes are in positions of least pressure from the valve springs and all the slack is where the adjuster needs it to be.

[DGXSER]

Excellent info Prom!! I knew it had to be something like that, even if I was at the wrong end of the rod (story of my life..).

[prometheus578]

Well, one of my original theories was related to cylinder pressure. We've all, for one reason or another, cranked over an engine by hand (with the plugs in), and seen it rotate back a few degrees when we stopped cranking due to a cylinder being on a compression stroke and the pressure pushing the piston back down. That would put slack back on the rearward side.
The "C" mark, in this theory, being where the crank is fighting the least amount of built up cylinder pressure
But, if that were the main reason, then the instructions for cam chain adjustment would have read something like this:
STEP #1: Remove the spark plugs.

[Crazcnuk]

Personally, I think the cam lobes are pretty evenly spaced. I doubt there are any 'gaps' where it would make any difference to the cam chain.

I suspect that the 'c' mark was there for some other reason, and it just made a convenient spot for the directions.

[prometheus578]

Actually, at the time of the original discussion years ago I went down to see my buddy at the Yamaha dealership. He dialed the "Yamaha Dealer Tech Line" for me and I posed the question to the top mechs at Yamaha Corporate.

That was the answer I was given.

[cywelchjr]

C'nuk, not to be argumentative, but pushing down on the back of the rear tire, would turn the engine backwards in relation to how it runs. When I ride down the road, the back of the rear wheel comes up. But I now understand your intent.

My concern is still this would not address the C mark, and admittedly I am not certain the reason it is so all important to be on the C mark. But it seems there would be a reason or they would not have put the extra mark on the timing plate just for setting the cam chain. JMO

My guess would be it's twofold, one to get the slack at the front where the adjuster is, and the other is probably to put the cams into a position where they won't pull that slack right back out when you release the lock bolt. I would think that in many parts of the rotation the cams would be fighting to turn the wrong way, which is probably part of the reason it can get slack if the bolt is not holding it tight enough.

At the "C" mark the cams are probably in a neutral position as far as rotational pressure generated by the valve springs against the lobes.

[Welsh1100]

Cam chain foolishness!!!

First off...let me say the everyone was correct! Doing what I did was a foolsh thing indeed. I understand that I dodged the proverbial "bullet" that time. There are several reasons why the manual explains how to make this adjustment. NO WHERE does it say to do what I did.
I hope that by posting this...that folks understand that I am not an idiot...per se...(LOL). Now I understand why my "old school" closed down and never reopened.