Timing etc.

Hi Tony, The ignition timing on the WD 16H is 7/16 BTDC fully advanced. Advance is usually tight wire, but mine has been changed to slack advance. So it depends which side of the mag the cable comes from. If it's the engine side, it's slack advance, if it's away from the engine, it's tight advance. Hope this helps.

Tight advance sounds dangerous to me, Dave. A broken cable and the engine is running on full retard - a recipe for overheating, burned valves and holed pistons. If Norton really did this, it makes one wonder if they had retards working in the design office!

Yes Norton did this, having just broken a cable recently (thankfully only a couple of miles from home) it would be interesting to know why Norton chose this option? Lost in the mists of time i suppose.

Yes Colin, I was surprised when I found out my 16H should be tight wire advance, as the other Norton singles I have are slack advance. Like you say it's a recipe for disaster. The lever would need to be stiff enough not to slip back as well.

Hence I wont be putting mine back to standard..!

Previously wrote:

Hi Tony, The ignition timing on the WD 16H is 7/16 BTDC fully advanced. Advance is usually tight wire, but mine has been changed to slack advance. So it depends which side of the mag the cable comes from. If it's the engine side, it's slack advance, if it's away from the engine, it's tight advance. Hope this helps.

Hi Dave,

I think you will find it is the other way around but correct me if I am wrong. If you watch the points spin on a 16H they spin anti clockwise. Therefore to advance the plate must turn clockwise. This means if the cable enters from the left, the engine side, it must pull the plate around: tight advance. If entering from right side, away from engine it would be slack advance.

Mag direction varies according to model year. Prior to 1934, both ex. and inlet cams were driven independently by the crankshaft. However, from that year onwards, the cam gears were meshed as a train, i.e. the exhaust cam driven from the crank and the inlet from the exhaust. As the mag chain takes its drive from the inlet camshaft, this reversed the magneto drive to clockwise (anti-clock at the points).

This system continued until the end of the engines with lever followers. Previous discussion on this forum indicated that the mag direction reverted to anti-clock with the change to flat-based tappets in 1948.

Any SV or OHV made from 1934 to 1947 will have a tight wire advance if the A/R cable enters behind the cylinder, as per standard. Tight wire seems to have been the norm with most manufacturers during the 1930s and beyond.

Perhaps the logic was that it seemed more natural and symetrical for the rider to pull a lever towards himself as he pulled away. The Amal choke sytem has confused countless newcomers to English motorcycles as well.

In practice, there is not much to cause the A/R cable to break and it can always be wedged at full advance..

My apologies, yes you are right Glen, the WD 16h mag spins the opposite way. I'd been working on an OHC and OHV Norton singles that day and had that picture in my head. Sorry if I confused the issue Tony. The best thing to do is take the cover off the mag and see which way the lever pulls it and which way the mag spins.

My bike is actually a 1938 ES2 and the points spin anti clockwise and it is a tight wire advance, cable entering from engine side. How hard is it, and what is involved in changing it to a slack wire advance; cable entering from the other side ? Seems like it might be worth doing if it's a relatively easy fix.

As far as I can see, all you'll need is a points housing with the cable on the right. Here's a link to a picture I've just taken. Both Anti-Clockwise mags, the one on the left is the standard tight wire advance and the one on the right is off my 16H converted to slack wire advance. I've taken the covers off so you can see inside.

http://s1080.photobucket.com/albums/j331/Horror/?action=view&current=IMAG2017.jpg

Previously wrote:

As far as I can see, all you'll need is a points housing with the cable on the right. Here's a link to a picture I've just taken. Both Anti-Clockwise mags, the one on the left is the standard tight wire advance and the one on the right is off my 16H converted to slack wire advance. I've taken the covers off so you can see inside.

Thanks Dave, Unfortunately I am on a ship at the moment using satellite internet an am unable to access the photobucket site due to restrictions on the server for some reason. Will be in port hopefully by end of week though and will take a look. I can't quite remember, what does the end of the cable slot in to ? Does this slot point need to be changed from where it is also ?

Glenn

I have just taken both mags apart. The cam discs are a mirror image of each other. There are a couple of slots opposite the slot used for the cable plunger that can only be used for the plunger head. I've taken the cam out of one mag and fitted it into the other and the cableoperatedit slack wire advance as we hoped. The only difference is the cam now works the points 180 degrees round from it's original position. I can't see that this will make any difference, the mag will need re-timed to suit. But I guess if you have to find another housing, it may be possible to find another cam.

I have found pictures from the Lucas parts book that have the part numbers you need

http://www.flickr.com/photos/9383961@N05/3262312853/sizes/l/in/photostream/

http://www.flickr.com/photos/9383961@N05/3263134030/sizes/o/in/photostream/

I would tend towards the 7/16. If that is too much advance, the engine will kick back when you try to start it and will pink when (if) it starts. 7/32 will probably start easily, but will overheat and burn valves if too retarded. Trial and error should make the timing right, and when you get it right make a note of it for future reference.

Thanks for those manual excerpts Dave. I know where there is another housing plate so all I will need to do is find another cam. I'm going to give it a go and change to slack advance when I find the cam. I will need a slightly longer cable as well to reach to other side of mag.