cam chain tension

[raz]

My cam chain tensioner is much softer than I imagined it would be, but I have no experience whatsoever to compare to. I can easily move it to its end using my little finger, with very little force. Can anyone describe how to know if the chain is fine, and the tensioner?

[pete roper]

While the spring on the new(er) type guzzi tensioner does seem a bit feeble it also seems to work quite adequately. Remember that it's only real purpose is to take up a small amount of slack on the long run between the oil pump sprocket and the cam sprocket. The wear in the pins of the chain i so small that any lengthening of the chain between the crank and cam sprocket is going to be so infinitesimally small it can make no discernable difference to the timing under load. On the over-run it may flop around a bit more but at that point it doesn't matter if the cam timing is out a few degrees. As long as it isn't out enough to allow the valve to clout the pistons, (And it would have to be out by a pretty large margin to allow that on a softly set up motor like a Guzzi.).

 

Compared to the original so-called tensioner they used in earlier bikes it's streets ahead and many high mileage riders, mostly on Cali's, have done in excess of 150,000 miles without changing their chains or suffering disasters so it must be doing something right!

 

Pete

[Guest ratchethack]

. . .On the over-run it may flop around a bit more but at that point it doesn't matter if the cam timing is out a few degrees. As long as it isn't out enough to allow the valve to clout the pistons, (And it would have to be out by a pretty large margin to allow that on a softly set up motor like a Guzzi.).

Pete, I've noticed from day 1 on my 2000 Sport, and also on other Sports and V11 LM variants I'm familiar with, that the motor will "miss" very occasionally at idle and trailing throttle, but never miss under acceleration or load. In my case, at first it was significant enough to quit at idle (~1100 RPM) until I installed a PC III. At that point the occasional miss decreased substantially, and decreased even more as it smoothed out and loosened up thru break-in. It still does it now, but lots less, and it no longer snuffs itself.

 

I've always imagined that just as you've said, the tensioner isn't fully controlling cam chain slack as it probably should, and that it's whipping a bit when not under load, throwing timing off just enough for an occasional miss.

 

Like Raz, I probably don't have anything quite right for comparison. My reference is SOHC and DOHC motors (both cars and bikes). The Guzzi camchain would seem to be loose by comparison from wot I've read. Do you think this occasional miss is due to cam chain whip?

 

Haven't noticed previous mention of this anywhere, but is there any sensible way to "stack it up" -- or best leave pretty darned good enough alone?

 

TIA