850 Commando Timing Chain Installation
Article by Mark Trotta
After the pinion gear is on, it's time to install the timing chain, cam sprocket, intermediate gear, and tensioner.
Tensioner and Plates
For proper adjustment and stability, it is important that the backing plates are installed correctly.
The inner bracket is thinner and installs long end facing down.
The tensioner goes on next.
If the rubber face is worn, replace it.
The outer bracket is thicker and installs long end facing up.
Studs and nuts are 5/16 UNF with internal (fan disc) washers.
Pictured below: camshaft sprocket woodruff key not yet fully tapped in.
The flat end of woodruff key faces engine.
NOTE: Camshaft and crankshaft keys are the same.
Valve Timing Marks/Lining Up Sprockets
When the chain assembly is ready to go on, the factory mark on the intermediate gear should line up with the pinion gear punch mark.
10 Pins Between The Dots
There is a small punch mark on both the intermediate gear and cam sprocket--these are the valve timing marks. Position chain so that there are 10 pins between the two marks. They will face up during install, and they're difficult to see once you put the chain around them.
Timing chain, intermediate gear, and cam sprocket are removed/installed as an assembly.
Proper Chain Tension
After tightening the two nuts, slowly rotate crankshaft assembly and check for tight spots. Hopefully there aren't any.
The factory manual calls for a maximum of 3/16" up and down movement. A little loose is better than a little tight.
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Notes and Misc
The chain was allowed to soak in engine oil for several days.
Because of it's high zinc content, Valvoline VR1 racing oil is a good choice for classic motorcycles. The silver container is conventional oil and has about 1400 ppm ZDDP. The black container is full synthetic and has about 1200 ppm ZDDP.
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