Wandering Exhaust Cam

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Wandering Exhaust Cam

Postby Iron Head » Fri Mar 29, 2019 1:35 pm

Recommissioning a ‘54 G80CS and noticed last night whilst kicking over to pump changed oil around that the exhaust cam processes outward then inward as it comes on/off the lobe combined with a light clicking noise. Will remove timing chest and fit a shim but was just wondering if this is regular occurrence?

Iron Head

Posts: 6002
Joined: Wed Sep 01, 2004 12:00 am

Re: Wandering Exhaust Cam

Postby SPRIDDLER » Wed May 29, 2019 2:31 pm

Yes, common.
This is because the lobes of the cams contact the tappet foot off-centre in order that the tappet rotates to even out wear of the tappet foot.
End float of the zorst and the inlet cam shafts is 'meant to be' adjusted by moving the inner bush but ideally this needs access from inside the c/case. Shims are fine.
To determine the end float of the blind inlet shaft fit too many shims so that the cover doesn't close. Measure the gap and fit shims of a lesser thickness than the gap. ;)
I poke badgers with spoons.

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