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Old 04-21-2010, 05:55 AM   #16
RedRupert
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Quote:
Originally Posted by kamanya
Hi,

I am sure the clatter is not metal on metal.

There are two chain guides per cylinder. One has the CCT pushing on it, the other is fixed on the drive side of the cam chain. The sound is generated by the static tensioner guide being slapped by the cam chain as a result of not enough chain tension on the CCT side guide. At low revs, as the cam goes past TDC the valve springs accelerate the cam to the point of removing tension on the drive side of the chain. The chain has some slack that once the engine has caught back up, it whacks the static guide as it is pulled tight.

Once the CCT's have come up to operating pressure the symptoms stop.

I am sure the CCT's once they get past a certain point of wear they "leak" more than designed and cause the clatter symptoms. It would be interesting to find out what causes the "wear" - certain oil? Debris abrasion? Tolerance issues?

My bike since it's little hiccup has run well with no return of the symptoms. It's still not the most mechanically quietest bike but this is what it seems to just be. I have a 990S too that's almost silent in comparison but I am sure that it's just missing some clattery character.

My 5c.

Interesting stuff. Plenty of fuel for thought.

I think my clatter sounded too sharp to be a plastic cam-chain guide. Don't you think plastic and metal would be more dull sounding?
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Old 04-21-2010, 06:21 AM   #17
skuikka
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There goes my theory:)
I put the more worn to the rear and bike was quiet at the start-up. I pre-filled the CCT:s. I'll leave the bike standing until the flue goes away and see then will it rattle.
I didn't have leek in the ball-valve either, the oil came out as you said, between the body and the piston.
If I understood correctly, the body is sealing the oil-pressure thats supposed to pressurize the tensioners so that it doesn't leak towards the chain and from there down to the sump.
If you have scoring in the walls of the hole where the CCT stays, and also the CCT has grooves in the surface, and then you swich the CCT:s around, I would assume that you would end up having lower pressure in both CCT:s. Would sound logical. Maybe.
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Old 04-21-2010, 06:50 AM   #18
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Interesting posts.

It was my rear CCT that went out first time and, based on the origin of the sound, I think it's the rear cylinder CCT again this time.

It does sound like metal on metal, but I went for some time before diagnosing the problem last time, and there were next to zero metal shavings when I changed the oil....
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Old 04-21-2010, 08:02 AM   #19
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Quote:
Originally Posted by RedRupert
Interesting stuff. Plenty of fuel for thought.

I think my clatter sounded too sharp to be a plastic cam-chain guide. Don't you think plastic and metal would be more dull sounding?
It is very hard plastic and I feel that if it were metal on metal there would actually be less of a noise.

It's precisely because its very hard plastic that it makes such a racket.

I could find no wear on the chains at all. Although, as you can see on my thread on this topic, the chain ate into the locking screw and the balancer, but that noise when the balancers were hitting the chain was very distinct from the normal start-up clatter.
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Old 04-22-2010, 02:40 AM   #20
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This photo is of my bad rear CCT.

Perhaps the band of wear is a clue? In the photo - about 4 mm wide and 16 mm from the chain-end of the CCT unit - it's not so obvious that it's a constant band in the photo, but it's easy to see that there is wear there. There was no such wear on the other good used (front) CCT that was quiet on start-up.

Could it be that the CCT is draining down by 4 mm too much each time? The start-up clatter is the cam-chain (slapping the rail, kamanya) while the 4 mm is taken up? That movement each time has shown up on the CCT body.

This bad CCT unit looks OK in other respects - It does not fall apart, as mentioned in the KTM Repair Manual. But could it be that the oil is seeping out from between the body and piston just a little too easily?
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RedRupert screwed with this post 04-22-2010 at 04:34 AM
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Old 04-22-2010, 04:47 AM   #21
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jamesbrown:

How about removing the 1 mm-thick copper sealing washers from the CCT plugs? Just to test. It'll be equivalent to extending the plug(s) by 1 mm. Not much, but if your symptoms are light, it might be just enough to make a difference.

You can get the front one out without removing bodywork.
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Old 04-22-2010, 05:26 AM   #22
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If the CCT is unpressurized, the spring will try to extend it but it's not strong enough, so when the chain hits it, it compresses, causing back and forth movement, so it wears.
I think the malfunctions can be caused by the clearance between the body and the piston being too large> loses pressure, the ball-valve leaking>the same. And theoretically, using worn out CCT:s for long enough, the CCT:s surrounding hole could wear so that the oil pressure for the CCT wouldn't be high enough.
The last one I don't think will be an issue, just a tought.
As I wrote, I dismantled one CCT. The collar pressed around the CCT is keeping the piston inside the body. While doing so it limits how much the CCT can extend.
For the function the CCT does not need the collar, it's just nicer to assemble.
But if the CCT would disintegrate when you take it out, I think that could tell that there is something else wrong because normally it shouldn't reach full extension because the chain and the chain guide prevent it so the collar should not be stressed at all. But if there is so much extension that the collar collar is limiting the extensionCCT, the chain must be lose

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Old 04-22-2010, 06:28 AM   #23
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skuikka:

Do you think the start-up clatter could be the CCT piston bottoming-out in the body?
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Old 04-22-2010, 07:29 AM   #24
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Quote:
Originally Posted by RedRupert
skuikka:

Do you think the start-up clatter could be the CCT piston bottoming-out in the body?
That's and interesting one!

Maybe.
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Old 04-22-2010, 08:45 AM   #25
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No, I don't think it's that. I think it's the chain rattling against something.
I filled both my CCT:s with 20/60 oil when I put them back, no rattle when starting.
So the tensioners can extend enough to tighten the chain, which means that they are not bottoming out.
Btw, When I looked at the structure, there doesn't seem to be any possibility to have problems if you put something between the CCT and the plug to give it longer reach.
There is only oil line coming in to the CCT hole, and no way out. So the spacer cannot go anywhere. Also the spacer would be constantly pinched between the CCT and the plug by the CCT spring.
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Old 04-22-2010, 05:22 PM   #26
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Quote:
Originally Posted by RedRupert
jamesbrown:

How about removing the 1 mm-thick copper sealing washers from the CCT plugs? Just to test. It'll be equivalent to extending the plug(s) by 1 mm. Not much, but if your symptoms are light, it might be just enough to make a difference.

You can get the front one out without removing bodywork.
I'm going to be back in the UK next week for three weeks . I've ordered some parts and, when I return, I'm going to experiment with a few things. I'll bump the thread then. Thanks for now everyone.
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Old 04-22-2010, 05:45 PM   #27
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Quote:
Originally Posted by skuikka
.
Btw, When I looked at the structure, there doesn't seem to be any possibility to have problems if you put something between the CCT and the plug to give it longer reach.
There is only oil line coming in to the CCT hole, and no way out. So the spacer cannot go anywhere. Also the spacer would be constantly pinched between the CCT and the plug by the CCT spring.
good point there, I've been running a spacer (I believe it was just a metric nut) between the CCT and plug with no ill effects for about 20 K now. My original CCT's were getting a little noisy (still at spec though) and that cured it.
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Old 04-22-2010, 06:02 PM   #28
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I'd be on the telly to these guys if I had these troubles. See when their CCTs will be ready for sale.

http://www.dirttricks.com/timing_chain_tensioner.htm
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Old 04-23-2010, 06:59 AM   #29
RedRupert
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I've been playing around with my bad CCT.

It seem that bottoming-out is unlikely to produce a metallic clatter (as the spring becomes coil-bound), but topping-out could. It also makes sense: if some oil is squeezed out via the cam-chain pressure, the few plunges that it takes in order to pump the CCT up would make a metallic clatter as the plunger extends and contacts the retaining rim of the body. It does not do so when actuated by hand, but placed between two aluminium plates, it does make a metallic tap.
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Old 04-23-2010, 07:02 AM   #30
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Quote:
Originally Posted by skuikka
Btw, When I looked at the structure, there doesn't seem to be any possibility to have problems if you put something between the CCT and the plug to give it longer reach.
There is only oil line coming in to the CCT hole, and no way out. So the spacer cannot go anywhere. Also the spacer would be constantly pinched between the CCT and the plug by the CCT spring.
I wanted to add a spacer, but didn't have the guts to try it!
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