How can I tell if cam chain is shot?
 

I'm trying to to track down an intermittent, erratic knock I sometimes get from my engine when it's not under load. I've read Mezo's great thread from 2014 on how a loose keyway on the counterbalance shaft can be to blame, but everything seems tight on mine.

So, working on the idea it could be a slack cam chain, I opened up the cylinder head cover and found the chain still snug against the sprocket with no obvious kinks or stiff sections in it. The cam chain tensioner is two thirds of the way in.

I'd be grateful for advice on two things:

- If the tensioner is that far in should I replace the chain?
- If the nuts and gears on the clutch side of the crank case are tight can I assume the keyways are also fine? (I don't want to go digging into parts of the engine that don't need digging into).

Thanks in advance for any help.

fotobucket

Cant see pic, but a worn camchain would "knock" (more like tapping, sounds a bit like loose valves) at idle, and very low revs, and the sound would go away as you put a load on the engine.

My tensioner was about halfway out at 125.000km, were I replaces it 'cause I had the engine open. You could tell the difference between new and old no problem, but im fairly sure it could have lasted way longer.

Without seeing a pic, og hearing the engine, my bet would be that it isnt the camchain.

You can see if the sound goes away if you install tensioner, and remove the spring. Then use a screwdriver ect and press on the tensioner and see if you can press the tensioner in a click more. Start the bike and see how it sounds.

Be sure to set the tensioner back to normal afterwards.

here you go, right type of chain this time :)

Here is another thread on cam chains
http://www.horizonsunlimited.com/hub...n-change-87669

Bob

Thank you for the advice. I've already pulled the engine out so, given the bike's history (it was running on half a litre of oil when I got it), I'm going to try to check everything I can without going so far as splitting the crankcase. Once I've finished making a tool to replicate the very expensive Yamaha fly wheel holding tool I'll try to get the cam chain out and do the stretch test. I know it's a tough one to get out but if I don't try I'll never be able to ride with the peace of mind that will hopefully come from knowing I've checked it all.

not sure which tool you need, to split the cases you can simply use long M8 bolt and push the crank out ...

check 3rd and 5th gears too :)

You don't need a tool to hold the flywheel. Put it in gear and apply the rear brake.
Here is some good advice regarding removal of the flywheel/rotor
http://www.horizonsunlimited.com/hub...r-clutch-53329
Do not press or hammer the threaded end of the crankshaft(use a hollow spacer as in the pic) or you will most likely damage it.

Bob

Thanks Bobmech. I'm finding my way with all of this as I get deeper into the engine and your great spacer idea could have saved me from disaster. I've already taken the engine out so the gear/brake thing is not going to work for me but I've made the tool now so will try it tomorrow. Do you think it's ok to apply a little heat to the nut to help it release? I've read somewhere that heat and magnets don't mix but am not sure how much heat it would take to wreck the magnets.

Thank you too turboguzzi. I was going to go just far enough to check the cam chain was ok but if it's that easy to split the crankcase I'm thinking I'll accept I'm done riding for this year and do a complete rebuild over the winter so every weekend can be spent on the road next year. If I do that would you recommend changing the big end bearing even if it looks ok? Just because I'm there?

the way i block the crank from turning is by putting the rod at the 12 oclock position and inserting a nice thick square piece of would between it and the cases. you will have to hold the whole engine well of course!

Thank you tuboguzzi. That worked like a dream and saved me a whole lot of hassle. Now to get that rotor pulled off...

i used a 10mm steel plate to build a tool, three holes for the 8mm bolt to pull, one central hole for a 12mm bolt to push... even then it needed a few sledge hammer blows on the central bolt to free, not for the faint hearted...
i wouldnt do the conrod bearing if it feels ok.