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Old 08-25-2013, 04:42 PM   #858
Brevis illi vita est
Joined: Jun 2010
Oddometer: 4,614
Originally Posted by Mugwest View Post
This occurred to me months ago and i've just now been reminded to post it.

There is a homemade Hall Tester in the ADV Hall of Wisdom. It has simple instructions and a parts list for building a test gadget for R259 Oilheads that have 2 Hall sensors.

I was surprised what with Radio Shack turning into little more than a damn phone store that they actually had every part on hand to build the box.

OK, so the dread word Oilhead has been mentioned and the Airhead JimJonesers are sharpening their pitchforks and mouse buttons. WTF does this have to do with Airheads? i hear.

Easy, gentle Cultists:
The Oilhead Hall Sensor Timing Box can also be used to statically time/set your Hall sensor-equipped Airhead Beancan (those of you who haven't gone Back To The Future with points-in-a-can ).

The Oilhead test box has 2 LEDs to test the Oilhead's 2 Hall sensors. Since the airhead has but one HES, you'll use either of the test box's HES leads. (Yellow or Green if you built the box to spec)

So, do it. Build the H.O.W./Radio Shack test box and then use these connections on the male terminals of your Airhead's Beancan plug:

You then turn the engine so that the S mark is in the timing window. Switch the test box on, loosen the Beancan retaining screws slightly, and twist the entire can. At the very millisecond the LED lights up, stop turning-- timing is set. Tighten the beancan screws and go have a proper Tuscan lunch.

The Oilhead timing/test box essentially duplicates "Ignition timing device BMW No. 12 3 650" seen here in the factory manual:

I suppose if you were clever you could eliminate the 2nd LED circuit in the test box to make it Airhead-only. I built mine to replace my 1100's HES a couple years ago, and just recently realized it would work on the Airhead

Might be wiser to leave it as is for oilheads---can test two sensors. Handy on tech days if somebody comes slumming with an oilhead. More importantly, it gives you a redundant test box. You have two test circuits. if neither lights up, replace the battery.

Would be worthwhile to know how to test the test box. My understanding is the Hall is simply a switch.

" Automotive ignition and fuel injection Commonly used in distributors for ignition timing (and in some types of crank and camshaft position sensors for injection pulse timing, speed sensing, etc.) the Hall effect sensor is used as a direct replacement for the mechanical breaker points used in earlier automotive applications. Its use as an ignition timing device in various distributor types is as follows. A stationary permanent magnet and semiconductor Hall effect chip are mounted next to each other separated by an air gap, forming the Hall effect sensor. A metal rotor consisting of windows and tabs is mounted to a shaft and arranged so that during shaft rotation, the windows and tabs pass through the air gap between the permanent magnet and semiconductor Hall chip. This effectively shields and exposes the Hall chip to the permanent magnet's field respective to whether a tab or window is passing though the Hall sensor. For ignition timing purposes, the metal rotor will have a number of equal-sized tabs and windows matching the number of engine cylinders. This produces a uniform square wave output since the on/off (shielding and exposure) time is equal. This signal is used by the engine computer or ECU to control ignition timing. Many automotive Hall effect sensors have a built-in internal NPN transistor with an open collector and grounded emitter, meaning that rather than a voltage being produced at the Hall sensor signal output wire, the transistor is turned on providing a circuit to ground through the signal output wire."

What this means is the hall sensor is a grounding switch. It activates the test box light (or the ignition) by providing a path to ground when activated.

So to test the test box you would turn it on and touch the sensor lead to the ground lead. Light should come on.

The ignition test is to touch the hall output lead (center pin) on the engine side of the plug, to ground. This should make a spark at the plug. Confirms the hall is a grounding switch.

BTW, doing that test is a pain. You need some sort of probe and have to fiddle it up into the plug while lying on your back on an anthill. I made up a probe out of a stiff piece of music wire. On end is hammered and fileed to the proper "pin" size to fit the plug. The other end has a female spade. All but the spade and plug tip are covered in heatshrink. It is just long enough to tuck into the side ventilation compartment of the timing chain chest. It bows slightly and stays in place. Good length to reach in with (10"?). Right where you need it when you need it. No cobbling up something while the ants invite relatives to the feast.

Methinks that test box needs to run on 12VDC rather than 9. Then you can run it off the bike battery so no dead or leaking 9V battery. Also could be extremely tiny.

Lemme think on that...Have a funny little LED light I made up once to illuminate a gauge...
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