Vr Upper chains- How much slack?

[peanut 0]

As per the title, just about to change the upper tensioner pad on a 95 vr. The engine was rebuilt not long ago with new chains and tensioner. Ever since it was fired upf rom the rebuild theres been a tattping coming from the head (same sound as sticking tappet) Just took the upper chain cover off and the tensioner pad is fooked. Two big grooves and the tip missing. Guessing there was something wrong with the tensioner bolt that screws into the back off the head creating too much pressure on the back of the pad. Might have even been overtorqued when refitted or not purged properly.

Could this have stretched the chains? or could it be the chains have a manufacturing fault and have too much flex?

Anyway...how much slack should be in the chain with the chain cover and tensioner bolt removed?

Ta muchly

Gav

[fla 9]

I'd be interested in this too - my perspective is slightly different, i want to know how far out the upper hydraulic tensioner needs to be, or how you ascertain when teh piston should come out to. I dont think there are any marks on the piston to give an indication though.

[dr_mat 0]

Quite normal for the tensioner pad to wear away after anywhere between 70k and 200k miles, depending on usage and phase of the moon..

The "tensioner bolt" applies no actual tension by itself, the slack is taken up with oil pressure within the bolt pushing a piston into the back of the pad.

[peanut 0]

Yeah but this one was worn down to the rivets in less than a thousand miles. Dont know wether this was down to there being too much pressure in the piston in the tensioner bolt or possibly too much slack in the chain

Gav

[dr_mat 0]

Yeah but this one was worn down to the rivets in less than a thousand miles. Dont know wether this was down to there being too much pressure in the piston in the tensioner bolt or possibly too much slack in the chain

Gav

 

Hmm, worn down in 1k is definitely wrong ... ! I can't see how excess chain slack could cause this - it's supposed to be slack!

 

The only reason there might be excess pressure is if the bolt was over-pressurised when it was fitted, oil pressure is unlikely to be enough to have that kind of effect. The bolt has a non-return valve, so on fitting it is supposed to be loose; then when you fire up the engine oil pressure takes up the slack; then as the chain gently stretches over time the oil pressure continues to take up the slack. It's a good idea to pre-pressurise the bolt when you fit it, but you need to be careful not to overdo it!

 

If that's what's happened, then whoever did it for you needs to replace the whole lot again!

[peanut 0]

It was me who did the rebuild and refitted that bolt and i purged it with the piece of wire as per the bentley, obviously i didnt do it properly. My concern is wether or not i should replace the upper chain again. Could it have stretched with the undo pressure on the pad?

Gav

[peanut 0]

It was me who did the rebuild and refitted that bolt and i purged it with the piece of wire as per the bentley, obviously i didnt do it properly. My concern is wether or not i should replace the upper chain again. Could it have stretched with the undo pressure on the pad?

Gav

[dr_mat 0]

Right, I guess so. I wouldn't have thought the chain would suffer too much, I'd just replace the tensioner pad and bolt.

But having said that, replacing the tensioner pad requires you to drop the gearbox off again so maybe you should replace the chain again, while you've got it off..?

I doubt it will have stretched much in that time, even if it was under excess tension, but if you want to be sure ...