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Why do we adjust camchain tension

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marroinia:
Hi there!

I'm preparing myself to open my engine head cover and put the missing dampeners back in where they are supposed to be, at the ends of the tensioner bow. As i'm thinking about the damages it could lead to if riding to long without them, I struggle to understand why do we have to slacken the bolt to adjust the tension:

A/  As the camchain wears loose, the bow isn't pushing anymore because the pushrod is kept in place by the tensioner bolt?

B/ As I'm riding hard, the cam chain push against the bow that is forcing back the pushrod that stays here, kept in place by the tensioner bolt?

C/ Both?

D/ You can't understand my french gibberish!

help me please,
Cheers!

Nurse Julie:
A. It is a self tensioning system. You just undo the bolt to allow the tensionsioner to reposition itself depending on the wear of the chain.

marroinia:
Ok, thank you to make it clear, Julie!

My bike is 25000km old, around 16000 miles, the camchain should be ok for another 20000km, what do you think?
And if the bottom dampener is missing do you think I can stick it or attach it with a very thin copper wire or fishing line to the tensioner bow an drive it carefully in the horseshoe by the top of the engine?

Nurse Julie:

--- Quote from: marroinia on February 15, 2020, 01:16:27 PM ---Ok, thank you to make it clear, Julie!

My bike is 25000km old, around 16000 miles, the camchain should be ok for another 20000km, what do you think?
And if the bottom dampener is missing do you think I can stick it or attach it with a very thin copper wire or fishing line to the tensioner bow an drive it carefully in the horseshoe by the top of the engine?

--- End quote ---
Can't comment on the cam chain as even though it's only done 16000 miles, who knows if the bike was ridden sensibly and had regular maintainace or has been thrashed everywhere. You always take a risk when trying to fit something down in the engine, it could fall off of the wire and get jammed down in the crank case somewhere. Why do you not have dampers fitted?.

marroinia:
Well, I checked the chain last time I tried to unlock the horseshoe, it wasn't possible to lift it out of the cam sprocket even with the tensioner fully loosen.  I unlocked the horseshoe quiet easily, now its moving free and the whole thing seems to be under proper tension... So i guess the bike have been rode without servicing but not long enough to do major damage to the pivot.

The previous owner rode only a few hundred kms out of Paris with that 400. He told me the head gasket have been changed while valve gasket or guide (?) have been replaced, the bike was smoky and capricious.
The job have been done by a friend of him, a "professionnal". I'm pretty sure he forgot tu fit the dampers back when mounting the head, I'm also pretty sure that no serious professional was in the place as the whole bike was a mess of approximatively done job. Nothing broken, just a bike left to unaware people.

I've never seen smoke and she running great at first or second kick since I tuned her properly.

I figured out the missing parts after I put back everything together! :( Looking at cmsnl drawings, I saw the damper and I understand there is no damper in my bike, at least the top one!

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