A review of correspondence from NOC-L
The Mk.lll tensioner
Noisy primary due to insufficient oil supply to tensioner
I have had a Mk.lll for many years and worked on several others. After the bike sits for a week or so it makes a god-awful racket when the throttle is blipped. After riding for ten miles or so, the noise goes away. Other Mk.llls experience similar noises.
The cause is that the oil leaks out of the tensioner unit as the bike sits allowing the chain to go slack. Oil gets into the tensioner from a trough formed on its top by the sheet metal piece, into which oil drips from the top run of the chain. If the tensioner gets full of clutch crud, which it eventually will, oil can not get back into it, resulting in the noise you describe. The cure it to take is apart and thoroughly clean it, including the tiny holes in the piston and body. Mine is now taking longer than it should to quieten down which means either that the primary chain is getting tired or the tensioner needs cleaning as I haven't done that for maybe 10,000 miles.
Thomas Allen (firstname.lastname@example.org) on NOC-L 27th. May 1998
Procedure for cleaning up the chain tensioner
Tom is correct; here are the steps I took to eliminate this problem on my Mk.lll:-
- Dismantle the tensioner and clean it thoroughly
- Reseat the steel ball in the check valve
- Ensure the slot in the check valve body is oriented 'horizontally'
- Ensure the tensioner body is dead flat, front and back
- Ensure the steel tensioner cover plate is dead flat
- Seal the steel cover plate to the body with silicone
- Reinstall, fill with oil and bleed
Mine (fingers crossed) now does not lose its prime. Even when I took it out of storage in the Spring, the tensioner still worked fine right from a cold start.
Greg Krikorissian (email@example.com) on NOC-L 27th. May 1998