Questions? Looking for parts? Parts for sale? or just for a chat,

The WD Motorcycle forum


WD Motorcycle forum
Start a New Topic 
Author
Comment
M20 Timing in Degrees

Does anyone use a degree wheel to time the M20, if so, please give the procedure. I would like to know if my idea would work.

Thanks,

Kenny
Oklahoma, USA

email (option): knbright@cableone.net

Re: M20 Timing in Degrees

You should check this on the internet...There's a formula using stroke and con rod length...I worked it out once and from memory I'm pretty sure it's 33 degrees BTDC fully advanced....Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

Hi Ian

Did you ever finish your timing device you were working on some time back

Br

Job

email (option): jonnyob1@googlemail.com

Re: M20 Timing in Degrees

Embarrassing this one...:pensive: ...I've built two complete bikes and started another while the parts for this have been sat on the shelf without moving!..Crazy, as to date I have around £1000 tied up in the parts that make up this modification(including a batch of gears)....

Due to the current situation I can't get to the engineers to have the last batches of bits made, although I do have the patterns and drawings ready to go...Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

Apparently there is a similar 'vernier' pinion available for Norton's. Horror has two in operation. :+1: Ron

email (option): ronpier@talk21.com

Re: M20 Timing in Degrees

It's not a vernier pinion...Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

OK! That's what Horror calls his?? Ron

email (option): ronpier@talk21.com

Re: M20 Timing in Degrees

I think that 'H' has a set-up from Andy Marks. It's an adjustable sprocket but it isn't a true vernier as it has set intervals and no way of splitting the difference.

Norton used the same term on the late Commando isolastics, but it was simply a lock-ring adjusting system with some peg holes...

https://www.kingpincomponents.co.uk/vernier-sprockets

Re: M20 Timing in Degrees

Andy Marks vernier mag sprocket has 17 hole positions in the sprocket with 1 less or more (I can't remember now) in the centre, which equals 2.35 degrees per hole.

Andy-Marks-Vernier-mag-sprocket

I wanted a finer tune so made my own. Andy was kind enough to send me a blank sprocket and I had 28 holes in the sprocket. I think mine works out at about half a degree. It's not 360 degrees divided by 28, but the difference between the inner and outer hole positions.

DSC-7157

DSC-7158

I must say it's so much easier that taking off mag sprockets. The centre never needs to come off the mag and it's easy to mark the position, take the mag off the bike and back on again without losing the timing. You have to make sure you mark the chain position as well on a Norton.

email (option): horror@blueyonder.co.uk

Re: M20 Timing in Degrees

I wonder if all these holes and the pin are really needed....... If you design it in a way that you could rely plainly on friction you could very simply make a stepless device.

And it don't need to be stepless all the way round, just a small portion to bridge one teeth would be enough.

So a sprocket with 2 or 3 slotted holes which could be clamped by a small bolts onto a centerpiece would do, or am I missing something ??

Re: M20 Timing in Degrees

That would certainly work...I do like the way Horror has made the adjustment more fine though...The common problem with vernier gears/sprockets are that the increments are too large and he has solved that one...Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

The outer washer with serrations would hold everything in place, but having the pin means you can take the nut and washer off and still play about with the timing with it holding in place. Then take the pin out and move it 1 hole either way will advance or retard the ignition. If you mark your original position you can easily put it back as it was. I'm not sure how you'd do that without the pin holding it in place.

email (option): horror@blueyonder.co.uk

Re: M20 Timing in Degrees

It seems like an awful lot of "fussing and fighting, my friend" for a 12 bhp side-valve single.

Whack the bugger on and ride it ! :slightly_smiling_face:

Re: M20 Timing in Degrees

Rik,Rik,Rik...Your worrying me now. Rivet counting levels of accuracy are just as valid for mechanical settings as they are for other aspects of the machine, perhaps even more so, as they relate directly to function..That must be respected....'There are many different rivets and many ways to count them'...as the vintage motorcycle enthusiast said...:laughing:....Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

Here Here What Ian said! Go stand in the corner Rik!

I do like the idea that once you've set your timing, you can then experiment or adjust it slightly with ease. Ron

email (option): ronpier@talk21.com

Re: M20 Timing in Degrees

Rik
It seems like an awful lot of "fussing and fighting, my friend" for a 12 bhp side-valve single.

Whack the bugger on and ride it ! :slightly_smiling_face:
It's actually so much easier that messing about trying to get the sprocket off with a puller, then getting the timing wrong when doing the nut up again, getting the puller again etc. I never need to take the centre off the mag. I've just bought another one of Andy Marks for my ES2.

email (option): horror@blueyonder.co.uk

Re: M20 Timing in Degrees

For the M.20 what I have done is to take the large idler pinion out and turn the mag pinion one tooth either way to advance or retard the ignition and then replace the idler pinion. Cannot recall the number of teeth on the mag pinion so in terms of degrees cannot say what variation this provides but it has worked for me over the last 50 years when I thought things were not quite as they should be.

Re: M20 Timing in Degrees

The trouble is, Ian that there are so many published timing settings for the 16H that three out of four are incorrect even by the standards of the day....they can only be regarded as a starting point. It's not like valve timing where I agree that there is a right and a wrong.

I do enjoy setting mine by the book, the trouble is that I sometimes forget which book :grimacing:

It's possible to clock a 16H through the centre timing hole using a 20mm reach gauge.

Dial-Gauge

Re: M20 Timing in Degrees

[' there are so many published timing settings for the 16H that three out of four are incorrect even by the standards of the day....they can only be regarded as a starting point.']

'Here's your new Norton Sir, we advise you make up your valve guide clearances and ignition and valve timing settings as you go along..'...Ian:laughing:

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

Sad, but true Ian...It seems to have been the Norton mentality...Before the Great War, when the 16H was the top sporting model, it was possible to pay extra for a BS or BRS...meaning the engine had been ridden round Brooklands in excess of 80mph by Dan O'Donovan in a slave frame...What no-one seemed to complain about was that the punter buying a standard model was guaranteed a slow one !

The valve timing can be set very accurately on the 16H though as the crank pinion has three offset keyways, each a third of a tooth different...Of course the factory never marked which one they'd used !:thinking_face:

Re: M20 Timing in Degrees

""Of course the factory never marked which one they'd used !""

What would be the reason behind that?? Just thinking: like BSA with its marked camwheels, its teeth has to be cut very accurately in relation to the cam. And for the crankshaft pinion the same, its teeth needs to be positioned in accurate relation to the keyway.

I can imaging that in case of the Norton with a choice of several keyways on its crankpinion this accurate positioning might not be necessary; no matter how the teeth are cut: the valve timing can always be close enough approached by chosing the correct keyway...???

Re: M20 Timing in Degrees

That may be true but what would be the benefit of cutting three keyways AND making the ignition timing more difficult to carry out for one engine...?...From a manufacturing point of view positioning the cam correctly in relation to the teeth, thus allowing the gear to be marked for setting wouldn't be a difficult engineering procedure...Most manufacturers did it...

I thought that maybe Norton used the same cam wheels in different engines with different cam profiles or cam timing and the different keyways would suit different applications (like Triumph)...

Triumph used '3 position wheels' as well and the SAME cam was set differently to produce the different performance characteristics of, for example, the T120 Bonneville and the TR6 Trophy....Ian

email (option): ian@wright52.plus.com

Re: M20 Timing in Degrees

The cams varied between OHV and SV, but the same crank pinion was used and although by the 1930s neither of these engines was being used for road racing, they were used for trials and it was probably part of the competition heritage aspect that owners expected to be able to fine-tune valve timing or to be able to use alternative cam grinds.

The pre-war manuals always refer to marked pinions...I've never seen any though.

Nieuwe pagina 1