Cam chain wear

[Guest]

Just getting back into rebuilding one of my 650g and noticed some strange wear patterns on my cam chain. One side of chain has pronounced wear to one end on each link. Obviously, this is the outside of chain, where it contacts the cam chain guide.

http://s200.photobucket.com/albums/aa36/eboyer/?action=view&current=PICT2079-1.jpg

http://s200.photobucket.com/albums/aa36/eboyer/?action=view&current=PICT2074-1.jpg

Not sure if this a big problem. Chain length is fine according to shop manual. Had noticed a chain noise around 2400 rpm. Should I replace or just slap it back together? Thanks in advance.

[robertob]

I would replace it personally. If you get one of the aftermarket chains with a press-together link you don't even have to split the cases.

Check your chain guides & tensioner - that sure looks like a bad guide, or a loose tensioner to me. Are there any signs that the chain contacted the head, cam cover or case anywhere?

[tkent02]

Something has been hitting it, wonder what?
As a comparison, the chain on the 750 I have apart now has no wear at all that is visible to the naked eye.
What do the tensioners and such look like? Any chance it was ever run without the tensioner, or with the tension released?
Maybe allowed enough slack for the chain to run against something metal?

[tone]

I'm not farmiliar with this exact model but the only time ive seen similar wear is on a very high milage engine where the cam chain guides are very badly worn :?

if this model has the slipper in the rocker cover thats worth looking at as ive seen them worn down to the retaining bolts on occasion apart from that i'm at a loss to explain the wear but would be looking at an extensive strip down to find the cause if it was my own bike

[Big T]

It looks like you have it out already, so replace the chain and both tensioners in the block. If there's one between the cams, do that one also. Cam chains should show almost no wear.

What do the tensioners look like?

[waterman]

Guys thanks for responses. Haven't had a chance to examine engine further to see what may be culprit. As to the condition of engine, not sure what previous owner had done. This was a "parts bike" when I received it but had to resurrect when my other 650g developed a spun secondary gear. Sad thing is that this parts engine ran perfect, with more zip. It had a great thirst for oil though, 12 ounces per tank of gas. Mostly lost through leaks but smoked on startup and slightly on running.

When I bought bike, engine was pumping oil from everywhere. Oil was gas contaminated and it had dissolved sealant used on cases. Right now, cases are split and cleaned for reassembly. Thought I ought to look at cam chain before slapping together. The rear guide appears grooved, will have to look at top and front guide. I will take pictures and post as I don't rightly know what a "bad" one looks like. I can't see where chain had made contact with anything metal, didn't find any shavings when pulled oil pan.

More than likely, I will contact Z1 and purchase new chain. Does anyone know if it is endless? Guess I can ask when I call them.

[Big T]

Since you've got the motor apart, get an endless chain. Easier to put on now.
renew everything that is plastic or "rubber" in the motor. Don't forget the O rings at the corners of the head gasket before you bolt it on - several others here made that mistake

[waterman]

I hear you about the corner orings on the head gaskets, have done that before myself.


Now how about some more pics. Pretty sure that the collective will find these to be badly worn.




May have got a little sloppy to contact down here.


As you can see, the grooves shouldn't be this deep I am sure. I think I may have found the culprit; cam chain tensioner. It seems to exert alot of pressure on the rear guide yet doesn't retract well.

[waterman]

Couple more pics.






Just sorta like to see my 550 in a blur behind the guide. Sometimes you get more in the picture than you realize.

[Big T]

I have to agree with your analysis. Get all new guides, chain and tensioner. Clean up those nicks in the case. Be sure and clean that spot where the bottom of the front guide sits.

Your's was converted to a manual tensioner, was it?

This is one of the problems any the older bike. You can never be sure what someone else screwed up and caused your problem. Or what part just got old and isn't functioning correctly. Except in my case, since I've owned since new.

Well, you can correct every problem now that you've torn it all the way down.

[waterman]

No my cam tensioner was still automatic, just seemed to only want to go in one direction. If it was manual, I think it would have worn less. Unless someone really cranked it down.

Now I am kicking myself for not buying a engine that was within a hour drive for $50 in Feb. Well, they always come available when you don't need them...