Hi all,
I found this on eBay.

Item No. 181091096350

Link:

http://www.ebay.com/itm/Top-Dead-Centre-Indicator-Triumph-Harley-Norton-BMW-Honda-Royal-Enfield-BSA-AJS-/181091096350?_trksid=p5713.m2061&_trkparms=aid%3D333005%26algo%3DRIC.FIT%26ao%3D1%26asc%3D25%26meid%3D6402531118879261424%26pid%3D100041%26prg%3D1010%26rk%3D3%26sd%3D300867636207%26

It is from Poland, and not expensive, I think.
We cannot use the M14 for the spark plug on M20, as the s.plug is positioned over the valves,
So the closest option would be the M10.
Do you think it can be re-died?
If so, what would be the thread for the ignition TDC inspection screw?..
I guess we would need to know the diameter of the inner pin of the indicator first, to know if there’s enough "meat" around to die..

Thanks,
Noam.

email (option): noam10@gmail.com

Hi Noam..This is similar to the device made for me by Joe Rosson,...I notice it is a metric dial gauge....001" increments would be more appropriate for British bikes, though you could do the conversion...The thread in the M20 head for checking the timing is only 1/4" diameter (6mm) and is Cycle thread, so the diameter of the inner piece would have to be small...I have used mine frequently in the workshop but only once 'in the field'...One drawback in that situation is that the petrol tank must be removed to give enough clearance....Ian

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

Hi Ian,

Thanks,

I also do not think that there is enough meat around the probe to be reduced to ¼”..
I use a stainless metal stick with 2 groves I scratched on it for TDC, and the ignition point above it.
The top of the "tool" is bent 90deg’and 1" to prevent falling into the barrel.
It works great and fit in your pocket / wallet..

BR,
Noam.

email (option): noam10@gmail.com

I do like the high degree of accuracy resulting from using the tool Joe made...However, an unrelated point to the case of an M20, is that most bikes have the spark plug at an angle...therefore vertical movement of the piston would not be identical to the angular movement of the dial gauge stem..Also it might be moving down (or up) the radiused head of a high compression piston as the piston falls (or rises)...My head starts to hurt if I think about this too much, but there would be a degree of inbuilt innaccuracy for many applications..(though not an M20)..Ian

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

I've been watching that as well Noam, it does look good. I used my magnetic dial guage base stuck to the frame, which was a bit of a fiddle.
You have to be careful on OHV bikes where the plug goes into the head at an angle, as the plunger on the TDC tool can get wedged and the piston wont move up. It happened to me once, so now I make sure the rod of the TDC tool is moving freely as all times and don't let the piston move it the whole stroke, just the last bit.

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

I use a big nail with two hacksaw cuts in it 11 mm apart works like a dream. Make sure the head of the nail is big enough to prevent it from falling in the cylinder.

I can sell these for 50 cent and still have a decent profit.

Henk

email (option): ahum@quicknet.nl

Hi Henk,

I looked in my wallet and found 2 euros. So that must be enough for 2 of those nails and the postage.

regards,

ramon

email (option): noahlevi6@hotmail.com

I all !

Ian, Horror- Correct. very clever points !

With an angled spark plug you should know the plug's angel and some trigonometry,
And as I recall, in those classes the teacher was sick
(Or was it me and friends riding out scooters to the seashore?...)

Those are few of the tools I used over time, as I could never find the last tool I used, when I needed it again.


Henk,
Do you have those wonder nails in stock at your Amsterdam branch?


Cheers!
Noam.

email (option): noam10@gmail.com

The item on e-bay shows a DTI with the range 0-10m which is not going to be enough to cover between TDC and 7/16 BTDC which is 11.1mm. So you need another DTI.

Otherwise, with the appropriate thread its not bad for the money. However you can knock up something similar for pence if you have a lathe and an old bolt or the thread taps to hand. I made one and had to use an extension on the DTI to get through the narrow timing bolt hole.

Cheers
Pete

I like the one made from a spoke Noam, I thrust it's an m20 spoke?

email (option): ahum@quicknet.nl

I used a toothpick, even cheaper...
See the Technical Info on the website.

email (option): viaconsu [at] planet [dot] nl

Before you go spending good money have a little think.
Plus or minus .001" is equivalent to 5 deg at the crankcase and that excludes play/wear in the engine.
To adjust the timing you have to remove the timing cover and this reveals the crank shaft nut so why not use a timing disc ?
As for setting the points +/- .001" = 2 deg at the crank.
And then you adjust this via a lever on the bars with no graduations.
So "special tools" might just be a bit of overkill on our bikes and way too sloppy for latter models

email (option): wariron@tpg.com.au

Henk WM20 2415

I like the one made from a spoke Noam, I thrust it's an m20 spoke?

email (option): noam10@gmail.com

Hi Trevor, you don't have to use a timing disc to set the timing. That is why people have markings on old spokes and nails etc and the timing is given as 7/16" or 3/8" BTDC. You can't measure that with a timing disc. It's also a lot easier to do than taking off the primary chain case, especially on a Norton if you've finally managed to stop the "Oil bath" from leaking

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

I think Trevor was refering to the crankshaft nut on the timing side of an M20, which can be easily accessed and is exposed anyway if you have the timing cover off for retiming...
Regarding the accuracy of any timing carried out I think it should be done as accurately as possible and and with any variables reduced to the absolute minimum...If it says 7/16" BTDC (.437") fully advanced...as it does for an M20...then it should be set as close to that figure as possible...
A casual attitude to the degree of accuracy required and the methods used to achieve it leads readily to substantially incorrect settings and the real risk the engine will be running with the timing retarded. (I've seen it enough times). In the case of a sidevalve engine, running for extended periods in this condition is likely to cause structural damage through overheating..
It strikes me as odd that great care is taken over things such as piston/bore clearances, valve guide clearances, gearbox bush clearances, tappet settings etc. etc. yet when it comes to ignition timing a measurable discrepancy from the manufacturers recommendations is deemed to be absolutely fine...
Yes, the engine will run with the timing incorrectly set and yes, it will also start OK....but is it running at its optimum settings?...probably not..and is there a risk involved?...Definitely...Ian

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

Plus or minus .001" is equivalent to 5 deg at crankcase? are you sure this is correct.do`nt know the degree before TDC for the WM20, but say it`s 40 deg, that would only make it .008" of movement of the piston,or am I missing something

There's (yet) another thread on the timing subject on the BritBike forum currently.

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=482214#Post482214

Its raised the question, for me at least, of the difference in degree timing between M20 and M21 given the different strokes but same length rods and recommended 7/16th BTDC.

Cheers
Pete

email (option): petercomley@web.de

The adv/rtd lever is only (sometimes) used for starting, for slow running adjustments and very occasionally for running in slow traffic, and it can't accurately be used at all as a means of adjusting the timing when riding..As the bike is running for by far the greater percentage of the time with the lever set in the fully advanced position, it really has no practical influence on the timing when riding, which is set at fully advanced... An alteration to the setting of the contact breaker gap width when fully open will only affect the timing of the spark if it is altered after the timing has been set...When setting the timing only an accurate determination of the exact point of opening is relevant...
Accurate piston position should be set with the engine being rotated in the direction it would be when running, with the piston coming up the bore to the correct position..this mitigates the effects of backlash caused by wear in the timing gears...
A dial gauge and degree disc can be used to accurately determine TDC at 'mid dwell'. Using a slip gauge pile or block of metal .437" thick the exact fully adv. position for the piston can then be determined.
The exact point of opening of the points can also be determined using one of the 'electronic boxes' currently on the market...
Then, after the drive gear has been replaced the results can easily be checked for accuracy...Using these methods the result will be as accurate as it is reasonably possible to achieve and, crucially, verifiable...You can stll save the other methods for an 'in the field' temporary fix that will get the bike running....
Next time you are doing the timing using a piece of welding rod or similar try doing it with no head gasket fitted...After doing the timing remove the head and check the accuracy of the result...repeat the exercise three or four times...You'll be surprised just how far out you can get it...I certainly was when I did exactly that experiment in the workshop.. TDC has to be found by 'feel'..The marks on the rod will be at least .010" to .015" thick and probably measured with a rule that has graduations at least .010" thick...Then there's your eyesight, both in accurately marking the rod and 'sighting' it accross the timing plug boss..and how accurately can you determine the point at which the contact breakers open?...You'll need to apply constant tension to the fag paper or shim as you turn the armature..Difficult to do accurately and even more difficult to achieve exactly the same result more than once...It is clear there are numerous opportunities for innaccuracy with these methods and with the head in place and using the same methods you will have no accurate way of checking it afterwards...
I'm not saying it doesn't work...I accept it does in as much as the engine will start and run...but it ain't accurate....Ian

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

Hi Peter...Piston speeds (at the same revs) is the obvious difference between the M20 and the M21...Less obvious is piston acceleration and deceleration before and after TDC, which will also be different due to the stroke difference and the resulting difference in conrod deflection.
How the two combine in relation to combustion times in the two engines?... I haven't a clue.. ....Ian

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

Bearing in mind it is the time it takes for the piston to get to the optimum position after the spark has occurred, in relation to the time it takes for combustion to reach its maximum potential after the spark has occurred that are the two relevant factors.(and which need to be the same) ..The M20 has a lower piston speed overall but a higher degree of deceleration as it approaches TDC and acceleration ATDC...The M21 has the reverse....Ian

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

And there I was hoping for a detailed, qualified explanation of the M20/21 combustion cycle differences.
Now could someone explain this "suck, bang, blow," concept to me please??

Cheers
Pete