Vintage Dirt Bike Q & A

Can anyone tell me if the elsinore coils are AC or DC the manuals i have in the wiring digrams says the MT 250 coils is AC as the wire from the ALT to the coil does not run through the rectifier however the wire from the ALT on the MR 250 that goes to the coil does run through the rectifier does this mean the MR coil is DC and the MT is AC??? or am I just looking to deep into it? any sujestions?? I am currently running an MT coil on a MR through the rectifier the spark is weak but it runs pretty well can this be the cause of the weak spark? because i have checked everything else. Thanks Ron

Hi Ron. It doesnt matter if you use Ac or Dc to power your coil. The silicon rectifier on the MR. does 2 things, first it coverts Ac to Dc for the lights,second it dumps excess voltage to ground so the lights dont burn out.(voltage regulator). Our MR has no lights left on it so when our silicon rectifier died,I bypassed it. I checked with the mechanic at our local bike shop,thinking it might do damage to the condensor or something but he said it was OK.and coils worked equaly well weather run on AC orDC. AS for weak spark, I also thought I had weak spark but a posting on this board said the elsinors never had great spark to start with. I find the right spark plug with the correct heat range a must. The mechanic also told me flooding the engine kills the plug real fast. Hope this helps.

Okay,
I have a wiring diagram for the MR 175 in front of me (Clymers manual). To by pass the rectifier do I take the blk/yel lead and splice it into the blk/white lead going into the coil? Now how do I rig the kill switch? Is the easiest way to place a switch between the coil and the alternator and break the contact or should I wire a switch that will ground out the output of the alternator to kill the ignition? How did the stock system worked, my wiring diagram is kind of vauge.
Justin

If you just want the ignition to work....Yep, just splice the Bk/Yel to the Bk/Wh.
If you want to use a modern CR style kill switch (or an old stock one for that matter), just connect one of the kill switch wires to your bike's Bk/Wh and the other to a ground like at the coil.
Remember, electricity flows the path of least resistance (like most of us). When the points open, electricity flows to the coil, causing a spark. When you push the kill switch button, electricity flows to ground rather than the coil, eliminating the spark.

Thanks. Now for my next question. To time the engine per the m.m. they have you disconecting the connector from the alt. and hooking a 6 volt battery and test light to the black/yellow wire and to ground. According to the manual the light will go out when the points are properly adjusted. When I do this the light will not go out no matter where what. What am I doing wrong?
Justin

I have to assume that the test light is connected between the battery and the wire to the points? ( - ) side of the battery to a frame ground, ( + ) side to the test light lead and the point of the test light (probe) to the wire. That is how it needs to be. Do not connect 6V or 12V to the points without some kind of resistor (test light) for this or the points and wire will burn up.

When the points close the light would get a ground through the points and turn on. When the points go open, the light would go out.

I always use a 12V battery and connect my timing light power leads to it and the inductor lead to the coil wire. Works like a regular timing light then.

Hi Tom,

When the points are closed the coil is energized. When the points open the collapse of the magnetic field on the primary side of the induction coil causes a sharp voltage raise on the secondary side. This high, thousands volts, is looking to go to ground and it finds it by jumping the gap in the spark plug.

Loren

_________________
Those who can make you believe absurdities can make you commit atrocities.

Loren Davis
51y

Yes it goes positive lead, test light, blk/ylw wire to points, negative lead to ground. Light does not extinguish. The points are opening, confirmed visually. Without removing rotor to continue trouble shooting I am guessing that either their is a short in the blk/ylw lead, or the ignition coil part of the alternator is shorted straight to ground. If it is the coils how much trouble is it to find a replacement, or will I have to learn how to rewind coils.
Justin

The only thing that should be in that circuit during this test is the points. The coil is a very long small diameter wire with the other end connected to ground. (coil of wire...)
A condenser will also look like a short in this test so make sure it is out of the circuit too.

If you have bad stator coils it is just about impossable to find them new.You can possibly find them on ebay, but then you take a chance they are good,plus they don't come up often.Sometimes you will have to buy an whole engine.The primary coil in the stator in my MR 250 was bad when I bought it but I was able to get it rewound at Custom Rewinds in Birmingham Alabama 1-800-798-7282.It took only 10 days from the time I sent it in to the time I got it back and cost 45.00. Works great. All the places I contacted before them would not touch it, ie the ones in the advertising sections of motorcycle mags,I think they did not want to be bothered with vintage bikes,but Mark Zimmerman of Walneck's Classic Cycle recommended them. Gary

Thanks all.
Sounds like I will have to pull the alternator rotor and see what is going on with the points and ignition side of the alternator coils.
Justin