Skip to main content
English French German Italian Spanish

1969 Commando cam Chain Adjustment sense check

Forums

Just checking I am on the right lines for adjusting the cam chain.

Timing cover removed No holding fixture for the intermediate gear but I can't feel any movement.  Engaged 4th and rotated rear wheel so that cam chain is running anti clockwise.  I am measuring the tightest point at the top run of the chain as the upper run goes from tight to slack. I have adjusted it to 4mm up and down movement at the tightest point with the engine being turned via the back wheel. Sound about right? Thx

Eddie

 

Permalink

I use a ring spanner or socket wrench to rotate the camshaft backwards. This neutralizes the forces exerted by the valve gear, removes any chain slack over the tensioner block and tends to allow a more accurate reading for the top chain movement. 4mm or 3/16" is fine but try and get an intermediate gear spindle support to confirm this.

Permalink

Hi Philip, Thanks. Sounds like a better idea.

Is the cam bolt LH Thread? Is it Ok to turn the engine over with it without risk of loosening it with a socket?

Unfortunately I don't have access to the gear support tool. 

Thx

Eddie

 

Permalink

Norvil sell an intermediate support. Two versions: one for Commando and one for Dommie. (No idea why they differ...).  Nobody is likely to cut up a "spare" timing cover nowadays. My Dommie intermediate shaft moved too much until I added bearing seal.  Before that, the support was vital. Since then, not so much.

Permalink

1 turn the crankshaft nut CW untiil the top chain run is tight as a banjo string (valve/spring is on any of the 4 cam opening ramp)

2 check the bottom chain run for being not to loose/tight on the adjuster/tensioner...tighten some if to sloppy.

3 holding the adjuster up lightly against the chain up with one finger, then tighten nuts.

Permalink

The only left-hand thread on the big twins is on the crankshaft oil pump worm gear. Everywhere else they are right-handers. The crankshaft and camshaft nuts should be torque to 50+ Ft lbs. So should not loosen, when turned with a spanner unless the engine has seized.

It is easiest and probably quickest to purchase the Intermediate spindle support tool but making your own version out of 6mm alloy plate is not difficult. They also pop up at auto-jumbles, along with manky, corroded or damaged timing covers that could be converted. 

See attachment for simple version of support tool. use a timing cover to spot the relevant hole positions.

I am not too sure why there are different commercial versions of this tool for the Commando and Dominator engines. Possibly the answer lies in the differing intermediate gears and spindles.

Permalink

I  took a cracked Dommie timing cover to make an idler tool for a Commando, the idler hole needed to be bushed to suit the Commando so there are small differences between the covers or the Dommie was modified for unknown reasons.

Permalink

By chance I've just acquired the AN version of the support plate. Here are the instructions, which may illuminate the Dommie/Commando difference.

Andover Norton gear support plate instructions

Permalink

Thanks for all of the information and replies. Struggling to justify the cost of the tool for one adjustment job

I'll give it another go in a few days. Contracted covid so laid up for a while. 

Eddie

 

Permalink

When replacing the cam chain back in 1980, I decided to check the upper run tension at several different points by rotating the engine (I know now that cam lobe loading affects the tension, but not then).  To rotate the engine, I sat on the bike, and with the plugs removed, slowly operated the kickstart with my foot while leaning forward over the tank, reaching down and gripping the chain with thumb snd middle finger - you may be guessing what happened next!  I carried out several engine rotations and tension checks, then did another rotation, forgetting to let go of the chain. My finger tip was drawn into the sprocket and the instant pain made me instinctively pull my hand away from the engine, which ripped the tip of my finger open like a flap.  A hospital visit to get the tip repaired then followed.

I didn’t try that tensioning method again!

Andy 

Permalink

I have done a little more digging around and found some answers regarding the respective  Dominator and later Commando Intermediate Spindle lengths....... As follows.....

PART NO  06 7531

Fits all pre-1969 Heavyweight twins

Overall length:   2.580" (65.5mm)

 

PART NO 06 1078

Fits all Commandos  1969 onwards

Overall length:   2.125" (54.0mm)

This is quite a substantial difference in length....11.5mm.  The longer spindle needed to accommodate the thicker, double gear pinion of the Dominator engines. The spindle dia being around 0.561"  (14.25mm) for both.

Permalink

I also was concerned at justifying the cost of a seldom used tool, but in the end decided to buy the AN one. Having used it I am sure that it was worth buying.

 


Norton Owners Club Website by White-Hot Design