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Adjusting distributor chain

Is it possible to adjust the slack in this distributor/magneto chain? I seem to remember reading that two of the three studs are smaller than the lower one and the mag can be pivoted slightly around it.  It's not the case with my ES2.

Also, the chain rubs along the top of the bolt holding the case in place - should it be a special bolt?

The bike I bought has so many odd bits and pieces I'm not sure what's genuine.


'ensure that the distributor chain has about 1/8 '' whip in one run. A slack chain will upset the timing.Adjust as necessary by slackening the two allen nuts near the upper edge of he distributor adaptor. A gentle tap with a soft mallet or gentle leverage will pivot the assembly about the bottom stud sufficiently to allow for normal chain adjustment.'

From Norton manual 1960 for 88,99 ,50 and ES2.

good luck


Hi Charles,  The "Allen " nuts appear to be something slightly different, Up to now I have not found a key to fit properly.  They are likely to be whitworth I think. Surprising that they were fitting these as early as1958  along with the Phillips head screws that secured the enclosed rear chaincase. Adjusting the chain without a slave cover is a bit haphazard .


... for your help. 

This is basically what I remember reading somewhere. However, I am not sure what studs are in my bike. I see that the AN exploded view only gives the information/part number for two of the studs. Should all 3 studs be the same or is one different? For the housing to pivot around the bottom stud implies that it is a tighter fit than the top two.

I'll have a closer look at mine.

Robert, what do you mean by a "slave cover"?



Hi Richsrd,

A slave cover can assist getting your cam and mag chain tensions correct. It essentially holds the intermediate sorocket shaft in exactly the right place so that when you have set the chain tensions with the cover off, they will be correct with the cover on.

In the past people have made these by cutting the 'ears' ( the parts that cover the cam and mag sprockets, chain tensioners etc) off another timing cover. Perhaps not so good an idea nowadays.

There is a tool available from Andover Norton that does this - see tool 06.7325. 

Knowing your import charge/timing issues, you could get one made by a competent engineering shop local to you. 'All' they have to do is mimic the internal shape of the centre part of  the timing cover, keeping a very close tolerance with respect to the dowel holes and the shaft hole. 

Hope that this helps you.

Regards, George. 


The intermediate gear spindle is easily pulled out of position by the cam chain which is loaded by the valve springs when a valve is open  , making it almost impossible to adjust either chain accurately . Some spindles get loose when the cam sprocket nut is undone/done up without the use of something to restrain the spindle.Most of us "old hands" have a cutaway cover.


The slave cover is only for the twins. The studs on the singles have a bit of play in their holes to adjust the chain. Check it in several places in case of eccentric sprockets.


... for your help on this.

It is in fact an ES2 I was referring to, but my Dominator is apart for new small end bushes so will use your advice when I put it together.

Are the three studs holding the distributor housing all the same, the AN exploded view is vague on this?


I have a set of Magneto Atlas cases, and the studs vary, one stud is waisted to the thread minor diameter for the width of the magneto flange to allow enough adjustment to get the chain tight. Its the same fitting as for a later Lucas distributor.


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