Wimminz – celebrating skank ho's everywhere

Well, after much faffing about, I decided to put the o’scope on the output of the ignition pick up sensors while cranking the engine on the starter.

Scope set to 0.2 V / div, get barely a div, if that, so < 0.2V

Now, at this time I don’t know what stock should be, but that seems way low, I’d have expected 0.6 at least, and then I hear back from the guys at Ignitech, their TCI unit takes 0.7 V minimum to trigger.

So, smoking gun found.

There are several issues here.

1/

Trying to find out what the original spec of the original pickups is supposed to be, if the iron core gets magnetised, even if the coils themselves are intact, this dramatically reduces the output, but, via oscilloscope or AC multimeter, unless you know what they are *supposed* to be, you are on a hiding to nothing.

2/

As you can see from these, and the photo attached, Mr Yamaha, in his wisdom, put these pick-ups on the outer cover, together with the stator windings, which get removed when you pull the outer cover, leaving the main engine lump and the rotor and magnets on the crank… this makes it impossible to set the pick-up to rotor clearance… which is why, as you can see, in his wisdom, Mr Yamaha made these non adjustable, *normally* pick-ups sit on a small mounting plate with two legs, and 30 or 34 mm hole centres, so, har-de-har, yet again *I* have managed to pick something that is non mainstream.

Which makes buying pick-ups difficult, (I strongly suspect the two kinds of luck I will have trying to buy OEM parts is “fuck all” and “none”) because drilling and tapping and mounting “normal” type pickups on this plate is quite doable, but I have to get the gap the same as these, and the position, and I don’t just mean rotary advance / retard position, but also the third axis, pickup centre height so it sits in the correct place axially on the crankshaft and rotor.

I strongly suspect it will be the P2 type from http://www.ignitech.cz/en/vyrobky/accessories/pick-up/pick-up.htm that I end up with, but it may possibly be a P6, because of the resistance, although there is a 1 mm difference in the “height” of the sensor from the mounting plate, which I could adapt for, but I’d rather not, wait and hear from the Ignitech guys…

*Their* problem is they haven’t come across non adjustable pick-ups before, so they are as much in the dark as I am about Mr Yamaha’s foibles.

You see, the real difficulty here, and the reason for writing this post, is that the issue is this whole approach to “black box” systems.

Resistors have colour codes, capacitors have values written on them, other components have part numbers and you can look up their specifications.

It is, quite frankly, fucking indefensible for the motor industry, or any other industry, to shift “black box” systems.

Me knowing from experience that generally speaking most of these pick up systems operate at 0.6 to 2.0 V at tick-over is one thing, it is still a huge range, but the factory TCI unit should state quite clearly what the minimum trigger voltage is (for Ignitech it is 0.7 volts, ideally this data should be on their website, but they are a small independent crowd so…) and nominal expected cranking RPM voltages, and peak voltages.

Similarly, the fucking pick-up units themselves should state not just their nominal resistance (the Haynes book of lies says 220, mine actually read 166) because frankly this just tells you if they are in one of three states, open circuit, short circuit, or something else but presumably working, but also the expected cranking RPM voltages, and peak voltages.

A coil with a highly magnetised fixed iron core is not nearly as sensitive to the “timing mark” lump of iron (in the case of an inert iron core with a very small energiser magnet on the end, which is what 95% of them are) or the magnet swinging by on the rotor.

One of the quick tests that you can do (apologies for getting the tube light reflection in this screen) is cover the sensor with a sheet of A4 paper, and swipe a screwdriver shaft across it.

This is 0.2 V per div, and 1 Ms sweep, so we can see the event duration is about 0.45 Ms, and we are getting about 0.15 V… it matters if your ignition is set to trigger on the rising spike or the dropping spike too….

This is bog standard laser printer A4 paper I am using , 80 gsm, is approximately 0.1 mm thick, so now we fold it in half twice, 4 layers of paper, 0.4 to 0.5 mm thick, remember the ideal pick-up / rotor gap is always around 0.8 mm irrespective of the engine.

Now the more eagle eyes of you will have noticed there is no second o-scope trace pic, because this time the ripple was negligible, the inverse square rule is at work here, and we are only at half the ideal gap, so that would give me a quarter of nothing.

Sure, the rotor itself has a much bigger lump of metal than the screwdriver so will generate much more impulse, hence me getting just under 0.2 V at cranking speed in situ with the proper Mr Yamaha gap, but it becomes interesting because the proper in situ output, which you can only test by fitting new gaskets and lube oil and replacing the outer cover properly, and the dismantled swipe with a screwdriver shafy with a pice of A4 paper in between, are broadly similar in pick-up output voltage terms…

Measuring magnetism is a lot tougher, suffice it to say that the cores of MY pick-ups will *easily* hold a teaspoon by the bowl, where easily is you feel it jerk as it released when you pull it away.

The rotor on mine is non magnetic, (yes, there are magnets INSIDE the rotor, that excite the stator coils….) as such, there is just a turned slot, and the timing mark is a block that is raised in this slot 2.5 mm, and about 15 mm long, so you see, these dimensions and so on are quite important.

You can see the bit I am talking about here, just above the hollow alloy pipe propping the started bendix to stay on.

So instead of being able to buy or order something according to a spec, which is what it should be, we are presented with “black box” components, and even if you know general ball park numbers for these things, it still isn’t good *enough* for you to go out and order something.

I actually have an untouched spare engine, of unknown internals condition, just bought it just in case, but these parts in that one will be 30+ years old too, and most of the people selling bits on fleabay are selling 30+ year old second hand parts, and know nothing either.

I’m actually at the point where it is almost as easy to retrofit and build a brand new system, and not because the engine is so complex or so precision or so old or anything else.

Because of “black box” engineering, where actual specs, if ever known, never left the design department.