Re: [alfa] Buzz in 1750 at ~ 2300 rpm

["David Jarman" <jarmanhome@xxxxxxx>]

I have to agree, I think this buzz or rattle is maybe a worn upper chain that
refuses to be adequately tensioned.  Roller chains stretch with use, and since
the tensioner is a simple spring loaded device (bless its little heart) with
an idler sprocket, the farther the tensioner extends out of the bore, the less
spring pressure is available for tensioning.  That's my theory, anyway.

I tension the chain using the familiar "roll it forward" method, but I remove
the spark plugs to reduce the effect of compression bounce.  In this manner,
when I preload the chain by rolling the car forward in gear, the engine
rotates smoothly and places a visibly consistent pull on the tension side of
the chain.  I then chock the front wheel, pop it into neutral, reach into the
front cover and push the tensioner in a couple of times, releasing it quickly
to allow it to pop back out with spring pressure, and then retighten the
tensioner lock bolt.  I always wind up with a minimum of play between the cam
sprockets, just as it needs to be. With all due respect to the late (great)
Pat Braden, I do not use a big screwdriver to tension the chain, because I
believe that can overstress the bushing the idler sprocket rides on.

Dave Jarman
Lexington, KY
USA
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided