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Jdeks 01-06-2013 05:56 AM

950 Cam chain tensioner jammed, bolts below 6mm
Hi folks,

Got an '04 950 Adv with 65000km on the clock, checking the cam chain tension as part of a service. Following the service manual and the HOW, except due to a lack of a 14mm allen key, I'm turning the engine over from the water pump wide with a socket on the balance shaft nut. However I'm turning it such that fron the generator side, the engine is turning counterclockwise as per the manual.

I put the rear cylinder at TDC (all cam lobes pointing in, crosses against the gasket head), unscrewed and measured the tensioner bolt. It doesn't even touch the tensioner - Have to screw it in about a turn before it makes contact. Actual measurement from case to washer is about 5mm once screwed in to make contact with the tensioner. The tensioner itself is and long and springy as the new ones I have.

Put the front cylinder at TDC (all lobes facing out, right?). Did the same thing, got the same results. Bolt needs to be screwed in to even contact the tensioner. Tensioner itself will not compress more than about a mm under finger pressure. Seems jammed.

Have I screwed up/missed a procedure somewhere, or are both my cam chains really that clapped out? IN the few thousand k's before the service, I was noticing sporadically a much more pronounced start up rattle that wouldn't go away for a few minutes, unless I killed and restarted the engine.

Thanks !

Peanuts 01-06-2013 06:19 AM

You sound like you have the tensioner fully extended - which is correct

You then screw in the tensioner cap (without the washer) until you feel it tighten against the tensioner.

The distance from under the cap head to the cylinder has to be 6 to 11mm. If you have 5mm then the chain and tensioner rail ought to be replaced.

That sticky tensioner will have caused your rattle, similar problem with the enduro bikes - that is cured by using a Dirt Tricks tensioner,

Jdeks 01-06-2013 06:26 AM

Hey mate, thanks for the snappy reply :)

The original plugs (short ones) are the ones in the bike - it's an 04 model. I have some shiny new long ones though, if need be. I put them in to test them, IIRC they give me about 7mm from base to washer....but I don;t know if just whacking them in is an adequate solution?

Now, you say measure without the washer? But the service manual says "Measure the distance between the sealing washer and the cylinder head". If I screw in the plug far enough to just make contact with the tensioner, I'd say it's be *just* over 6mm from bolt head to cylinder.

But I was under the impression that I shouldn't have to screw the bolt in AT ALL to get contact with the tensioner (if the chains are in spec).

Peanuts 01-06-2013 11:36 AM

Yes, you are correct. Keep the washer on.

I was sure the design of cap had changed, but cant find anything in the parts fische, so I guess they altered the fische for the early bikes so all models now fit the later caps.

Therefore if you are in spec with the later cap I recon you are good to go....... lets see what others think!

Jdeks 01-06-2013 05:52 PM

I'm not sure...I really don't like the idea of just 'replacing the ruler because it's not measuring what you'd like it to'. SOMEthing has worn, and while I'm this deep in engine bits, I think I'll go ahead and replace them anyway.

Thanks for the help

Head2Wind 01-06-2013 08:24 PM

The later model caps were extended (longer) to increase the tension on the chains AND provide more effective stroke of the tensioners. EDIT: The fiche seems to not reflect this.... not sure if this is 100% accurate. I have a 06 ADV on the rack right now that I can measure the caps on to compare to your 04.

If the new style caps get you within service limits again, then I would run them!

It does not take much change in chain length or surface wear on the guides to make the early tensioning system go "out of spec". What I have seen comparing a new chain set to a old set is something to the tune of 1mm maybe 1.5mm difference in length is all.

Head2Wind 01-06-2013 08:31 PM

If you do decide to go with the full service replacement of timing drive systems, it means you should also replace both the front and rear guides for both cylinders, chains, tensioners.

If its a early motor that has the early head nuts still I would also update them at the same time....

Can be performed in the frame, however you will need a 14mm hex drive for turning the crankshaft to perform this work because the aux shaft will need to be removed to get the chains off/out.

Jdeks 01-07-2013 04:47 AM

Hi H2W, thanks for chiming in.

The later caps do indeed get me within spec - 7mm from washer to cylinder.

Okay, I don't need to be told a third time not to spend money :evil. If you both think the longer caps are good enough, I'll just run them. I've read around a bit more and had a look at somediagrams and by the looks of things the early tensioner were just overly conservative in their tolerances.

I'll let you know how loud the bang is when it grenades :P

Thanks for the help.

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