Cam chain too much slack?

Hi all,

I went on a test ride and I heard (only for a moment) a noise like a chain rattling in the engine somewhere. This was preceded by a ticking noise at the top LH corner of the engine.... which went away when the engine was warm.

Both incidents made me decide to take the cover off (what a pain, even the coils have to be removed to do that!) and have a look.

All looks fine with the camshafts, and with those that I can measure, all the valves still have the right clearance. For some reason the bike doesn't turn over anymore on the starter so I can't check any of the others.

However, when looking at the cam chain, with the (ZX10) tensioner still in place, the chain stands proud of the inlet cam gear and between the two shafts is very slack. See video. In the engine the chain is taut. The tensioner has 19 clicks to its end and when pushing it in by hand I get to 17 clicks, so there is some left, but not much!

Is this too much slack and is the noise I am getting the chain rattling on the cover? If that is so, with the tensioner still in place, is the chain too far gone? I measured it when putting the engine together and it was well within tolerance...

Anyway, if it's gone it will have to be replaced.... can that be done without taking the head off? (cut the chain, link to the new one, pull through and then somehow compete the new chain- I have not seen any 'connecting links' on it like on a bicycle chain...)



Cheers
Paul

Hi Paul,

Hate to tell you mate, but that is FAR, FAR TOO MUCH slack on the chain between the cams. I would not risk running that in fear of it jumping the gears.

As long as you have routed the chain correctly over the gear and rubber wheel on the cam chain tensioner arm (which the tensioner pushes against) then its definitely time for a new chain.

Oz & Deb sell a cam chain with a soft link which you can see on their site.

Pete F
UK

Yeah... thought so.

Ok, I'll contact Oz and get a new chain.

Thanks Pete!

Paul

I'm not buying it. Something is wrong with your ZX 10 tensioner mod. Not sure what but if the cam chain has that much slack then the tensioner is not taking up the slack. The fact that you're at 17 clicks out of 19 indicates a problem. As I remember it, a reasonable worn chain with the ZX 10 tensioner mod usually comes in at 10 to 11 clicks.
Before jumping to the conclusion that the chain is worn beyond the service limit, you need to measure the chain as per the manual page 191, table H57.


If this measurement indicates a chain beyond servicing, then replace the chain. If the measurement indicates the chain is within service limit, then you need to sort out the real issue.

As for running the bike with that much slack in the chain- I agree with Pete. Way too much slack in the chain. I would expect about 4-6 mm of up and down movement would be acceptable between the 2 cams as shown in your video.

Thanks Kawboy, I measured and from the centre of link 1 to link 20 is 12.2 cm. I am sure I measured the chain before I put the engine back together as I measured the primary and secondary ones and had to replace those... but consciously decided the cam chain was OK.

Also, when I was setting the timing and valves, the chain was far tauter at the top....

?

So what can be wrong?

Pete, re your earlier comment, on page 25/26 of my long blog I recount how I installed the cam guide wrongly and how Kawboy told me where to find the pic in the manual to do it right, so I am pretty sure that is not the issue... but if there is a way of checking without taking the head off....

Just be very careful if and when you change the chain I ran into a problem with one of mine where I had the head and put the chain on not realizing it wasn't seated properly on the crank sprocket (it was in fact riding on the side of the crank sprocket) put it together and rode the bike for a good 20 kms the engine locked up and I had to get it towed home (because the chain valley is right under the frame backbone (stock frame) I hadn't noticed the problem.) luckily nothing was damaged other then my wallet for the tow (lol)