Setting up ignition timing, 1960 Model 31 K2F mag

[mjf65]

Morning all,
After a long pause and now Sean Hawker has worked his magic on my sparkless magneto, it's time to fit it. As a complete novice to British bikes, the last time I dealt with points was my Z250 over 40 years ago. Has someone got a step by step guide for this, sort of check sheet style? I've read the manual a few times and Sean gave me a few tips but any additional information would be great. I've also watched a rather good video on YouTube of someone setting up the timing on a G80 but can't find any filmed tutorials for any of the twins?
Thanks

[Groily]

It is hard to improve on the instructions in all the manuals to be honest, and not sure if there are any vids out there.

But anyway, my tuppence worth if it helps . . .

Decide whether you are going to set the timing using the time-honoured 'rod-down-plug'ole' method or using a degree disc. Most people probably still use the rod-on-'ole method, so doing in that way . . .

. . . first get your pistons to the required distance BEFORE top dead centre. Both pistons move together, so one will be on compression and the other on the exhaust stroke. The one with the valves shut is the one on compression, which is the one you want to focus on (you can see an open ex valve on t'other one with a torch down the plug'ole usually, which helps).

When setting piston position, do it by rotating the engine in its direction of normal rotation - that way you don't get any backlash (which you will if you reverse the engine to find the right spot.) Check book for distance before tdc recommended for your engine - 3/8ths inch from memory, which may be faulty.

When you have got the pistons where you want them, don't touch anything except the magneto. Which you now need to place in the fully advanced position using the lever. That is with the cable slack - the plunger at the mag in its fully-'down' position - and make sure it actually operates properly from the 'bars. Poor operation is not rare . . .

Then loosely put the drive pinion on the shaft. Turn the magneto in the direction of rotation - ie anti-clockwise from the DRIVE side, clockwise from the points end - until the points are JUST opening on one of the lobes of the camring. Time-honoured method of knowing when they are just opening is with a fine cigarette paper between them - when it starts to slide out, that's your spot. A 1.5 thou feeler gauge is good too.

Most people use the cam lobe on the right lower side of the mag (from points end) for this - because you can see the points more easily at top left than you could at lower right if you were to use the upper lobe.

Bear in mind that THE LOWER LOBE (rh side of camring looking at the points) FIRES THE REAR (gearbox side) HT PICK-UP and the front (engine side) pick-up is fired by the lobe on the upper left of the camring. (An error isn't a real problem - you'd just have to swap the spark plug leads over when the job's done - but it's surprising how many people get confused on this.)

When you are happy that

the mag is in the correct spot,
that it is fully advanced, and
that the engine hasn't moved,

put the pinion firmly on its taper and do the nut up. It helps to hold the things steady (no force though) from the points side while you just start the gear onto the taper. It should grab quite easily, but some are more worn out than others and it may take a couple of goes to get things done up without the mag spindle moving a bit. If it does move, no choice but to go back and do it again.

When all is done up, turn the engine a time or two, re-find your position before TDC and check that points are exactly where you think you had them. They should be, but . . .

It is also VERY worth doing a check on the other cylinder - get it on compression, correct distance before TDC etc, and are the points JUST starting to open on the other cam lobe? Errors of several degrees are sadly very common with K2Fs, especially manual ones, but not something to address in this context. One degree out on the mag is Two degrees off on the crank, remember, so it IS important.

Check also the points gaps on both lobes. Errors of a couple of thou difference are usually OK, and you can average it out with no detriment. Huge differences of many thou are not good though, and investigation + remedy is needed. That said, a modest difference in points gap is much less serious than an error in the firing interval between cylinder, and the two things don't always go hand-in-hand.

If using a degree disc, then the piston is set x degrees before tdc using the crank position, which is more accurate usually, and better for checking the settings on both cylinders.

Nothing, however, will confirm the firing interval dynamically across the rev range except a strobe.

For accurate measurement of points opening, buzzer tools are available. -Batteries and bulbs do NOT work with magnetos, and nor do any but the most sensitive meters because the difference across your points will be a resistance of half an ohm between their being open, and zero closed if thy are super-clean: most meters are fairly useless at those levels.

[dave16mct]

I can't think of a better guide than the manual. It is very clear and easy to follow. Make sure the points are clean and set to 12thou. Make sure you have the lever on full advance. Make sure the off-side is on compression (both valves closed) . The rear pick-up wire goes to the off-side plug. All this is in the manual. Good luck with it.
Edit: Sorry I didn't know Groily (font of all magneto knowledge) had answered this!
Dave.

[mjf65]

Thank you for your help. Sean's tips were to set the points gap to jut opening before fitting. Also check for compression on the cylinder you are timing with your thumb when coming up to TDC but I'll take the valve gear covers off as I checked and adjusted the valves and covered nearly 400 miles before the mag failed. Other tip was to ensure the drive gear can't slip as you tighten the locking nut, I was thinking of making up a small wooden wedge to do this? On the YouTube video the chap gives the gear a light tap onto the shaft to secure on the taper, is this a good idea or could it damage the mag? Also I understand both the taper shaft and the bore of the drive gear should be dry to prevent slippage?

[Groily]

Yup to Sean's tips, of course.
Just think in 'Ps' - Piston position, Points position and Pinion and you'll not go far wrong.

You can certainly take the rocker covers off if you like - but in my world that means seat and tank off and possibly having new gaskets handy - and that's work.

A tap to fit the gear can be good - but with it loose on the mag and already part-engaged with the inlet cam pinion, the gear shouldn't slip so I'm not sure where your wedge would go exactly. It's the mag spindle that needs absolutely not to turn as things go together, so a free running non-binding nut is a major plus. When the gear is firmly on the taper and you're final tightening, a spanner on the crankshaft nut can help, by opposing the leverage on the mag nut and stopping the engine rotating. That's better than wedging the gears, if that's what you're thinking. 'Dry' is probably good, too.

The common errors are setting the piston after not before tdc (I know, yup, but it happens quite a lot!), forgetting to advance the mag (ditto), and muddling up which HT lead goes to which cylinder (ditto squared). You can choose which way you prefer to have your HT leads - I prefer, like Dave, to have the rear pick-up go to the right-hand (or offside when I lived in England!) cylinder. But some people prefer the opposite, so set things to suit them.

[dodger]

Before fitting the mag in place I always lightly lap the pinion to the mag taper with a bit of fine grinding paste. clean both surfaces with thinners or methalayted spiritand leave to dry. Coupled with a free running nut the pinion won't slip when tightening the retaining nut.

[mjf65]

Thanks for the help, couple of additional questions;

What type of material do you suggest for the rod, hardwood dowel and how can you put this in at the vertical when the plug threads go into the cylinder head on an angle?

After finding TDC you then have to rotate the crank back to 11/32 (35 degrees BTDC) would you take the piston past this point and then rotate the drive in its normal rotation to achieve this to ensure any backlash in the gears are taken up?

Thanks

[clive]

An old full width hub spoke if you have one makes an excellent rod. Means you can stand it vertical obviously with the rounded end on the piston. Definitely don't use a pencil whilst doing a re-time for your ex. Then realise you have pushed the wheel forward and broken the pencil with an inch left in the barrel Think what the f... and start the bike. Worked fine but then feel guilty and take the head off only to find all the bits have already been blown into the silencer!

Oh yes and go back and roll forward to take up the backlash

[SPRIDDLER]

I made mine from a wire coat hanger. Thin enough to stand vertically in the plug 'ole. Obviously ( ) the tip of the probe doesn't have to rest on the centre of the piston as TDC is the same point on any and every part of the piston crown so just position the probe as vertically as possible as when you marked it.

Probe 2.JPG

CIMG4402 (480x360).jpg

[mjf65]

Again thanks for your help, I think a long tent peg will be perfect.