moetheshmoe

IV'E GOT SPARK! But boy have I learned a hard lesson. Not to mention time consuming and expensive. I bought new points, condenser, ignition coil and spark plug....and I didn't need any of them. If I had checked continuity when I grounded the plug against the head I would have realized that as old as this bike was the head had developed a 'crust' on it and the plug was not really grounded. I tested and tested the coils and the points thinking that was the problem. I cut and rewired, thinking that was the problem. Every one has said these old systems were pretty easy to figure out and I was just making it more difficult than it needed to be. Like they say "a little knowledge is a dangerous thing" Anyways, lesson learned and I think this bike is worth restoring. I'll post updates as I go along. Thanks Paul and everyone else who's helped. I appreciate it. Moe

Sorry about the photos but can you believe that they wouldn;t publish the source coil specs? Just the charge and lighting coil.

For anyone following this and has a similar problem, here's a link to an interesting answer http://answers.yahoo.com/question/index?qid=20090422164951AAR1nus

Boy, I just had a rude awakening. I thought charge coil and source coil were one and the same. Looking at my Clymer manual and they mention testing for lighting and charge coils and the specs - .19 and .27. Turns out those 2 coils are the 2 little coils that make up the lighting coil, they say NOTHING about a source coil. What tipped me off is the wire color - grn/wht instead of blk/wht. I can't believe I didn't catch that sooner. But even now I'm thinking 'how in the hell could they print a repair manual and NOT mention the coil that provides spark?' Incredible! Let me slap my forehead a few dozen times and I'll get back to you.

PS I do have a new ignition coil. I'll try the old and see if I get the same voltage as the new at the plug.

Well now I'm stumped. Your info and my readings say 2.7, roughly. Yamaha and Haynes say .27. My friend suggested I find an old lawnmower repair shop that's worked with the old point and magneto systems. I would believe that their numbers can't be too far different. I'll let you know. Thanks.

Well I never thought of this until now. I messed around with the point gap. When it was at .14 I got 6 volts. Smaller than that I got 3 volts. But when I increased it I got 15 volts! I still don't know if that's normal but what an increase. At the plug that 15 volts became 48, still not enough to fire a plug. Maybe the cam that built into the housing is too worn?

Just got off the phone with Yamaha Corporate office in So. Calif. and the only info they could find were some general specs that confirmed what my Haynes manual has said - .27 ohms for the source coil. Where did you find 1.7? Also do you have any info. on AC voltage output as it's cranking? And finally, does your bike vary resistance as the points oopen and close? Thanks.

UPDATE No. 2 I switched the wiring as you said and I'm getting 6 to 7 volts. But I did find this out - the difference between coil resistance figures depends on if the points are open or closed. 2.7 when open and .6 when closed. So, when the points are open it's measuring resistance thru the coil? Any thoughts?

Strangest thing. Before I removed the lighting coil the source coil had a resistance of 2.7(-.6) and after I removed it went to .7(-.6). It's been sitting in the sun for a while and I decided to reverse rotation with my drill and see if I could get more voltage, in case, like you said, I attached the wrong end of the coil. Still got about 5 volts, no difference. But I rechecked resistance and it's back up to 2.7, same as before.

Does it matter which end of the coil goes to ground and which end goes to the condenser?

UPDATE: I completely removed the ligghting coil and connected one end of the source coil to it's mounting post(ground). The other end is connected to the wire that comes from the condenser and goes to the ignition coil. Surprisingly, the resistance has gone down from 2.7 ohm to .7 ohms! And when I touch the 2 leads of my meter to check resistance it reads .6 ohms. If I adjust the coil reading(.7) by subtracting that .6 I get a net resistance of .1 ohms, hardly any. I hooked up the drill and checked for AC voltage generated and I get an average of only 4 to 5 volts. So I have very low resistance in the coil, along with no breaks and it does generate volatge but nowhere what it should be, which I believe is around 40 volts. The magneto as a whole seems tight when mounted and doesn't wobble. There is a little scoring on the cam surface but the points open properly and the gap is .14 so I don't think that's an issue. The question is "What's the issue?".

BY the way, the magnets feel strong. I can pick up a medium sized crowbar.

Well I put in the new points and condenser, rewired back the way it was and still nothing. When I hook up a drill to the crank and spin it the source coil averages about 6 volts ac being generated and the lighting coil averages about 4. I double checked the source coil resistance and it's 2.7 ohms, 10 times what the manual says - .27 and I don't think it's my meter. I set it on the lowest setting. Also, I disconnected the source coil to check again for continuity and there's a complete circuit there, no breaks. And the coil unconnected still shows 2.7 ohms. What does it mean when resistance in a coil is high but there's no breaks in the winding. And these windings look almost brand new. The lighting coil is also 10 times higher than the book says, unless the book is wrong? Could the magnets be too far away? There doesn't look like any adjustment. Help? Thanks

Well I tried it without the condenser and couldn't get a spark. I did hear that without a condenser you can't build up enough voltage for the ignition coil. I've got a new set of points and condenser coming in a couple of days. I'll put those in and let you know what happens. Please stay tuned........

Great! Your pic confirms my description. I'll hook it up and let you know how it works. Thanks.

Ok I think this is starting to make sense now. Not knowing much about electronics I thought the coil had to be isolated(not continuously grounded) and the points would provide on and off grounding. If I understand this right..not so. One end of the source coil is constantly grounded(thru the yellow wire-lighting coil) the other black n white wire is grounded thru the points when they are closed. During this time a charge is built up in the coil. When the points open and disconnect the ground the charge is sent up the black n white wire to the ignition coil. Is that right? If so, then I need to rewire back the way it was. I did check for continuity in the source coil when it was disconnected and there are no breaks in the coil. When it's hooked up I get 2.7 ohms yet my manual says it should be .27. I'm guessing that's ok, just a matter of the meter setting? Also the lighting coil measured 1 ohm, which may be a little low, should be .19. But as a general rule less resistance is good, is it not? By the way, the green n white wire which comes off of one of the two small coils that make up the lightening coil does not show continuity or an ohm reading. I won't be needing them unless I reconnect the complete harness but that sure puzzles me even more. So at this point I'm going to rewire back the way it was and I can only think of the condenser as the possible problem. While I'm messing around I'll try and bypass it and see what happens.

Thanks got it. Still need a wiring diagram for INSIDE the magneto.

PM? What's that?

Hi All, Moe here. It's been 30 years since I last rode an Enduro and I guess I still miss them. I just inherited a 1978 dt125E and I'm thinking about a total restoration...IF.....I can get a spark. I've posted under the question "Did the Factory do this" because it's all screwed up, makes no sense. I hope someone can help. Thanks!

Hi, I'm new to the club and hope someone can help me. I'm going bald and can't afford to pull out anymore of my hair. I just inherited a 1978 DT125E, with points and magneto. Trying to get it started and decide whether it's worth restoring. It has no spark. Could not get it to generate any ac voltage, even when I hooked up a drill to the crank and spun it. Took the flywheel off and the coils and points look good. But here's the strange thing - one end of the source coil was hooked to the condenser and then exited via the B/W wire which leads to the ignition coil. The other end was pigtailed with 2 leads coming off the lighting coil and exited via the Yellow wire. The lighting coil seems to be made up of 2 little coils each with 2 leads. One is G/W, the Yellow has 2 as I said and the 4th is grounded to the plate. So anything connected to the lighting coil is also grounded! So the points can not work. This can't be right, can it? Did it come from the factory this way? Or did someone butcher the wiring? It has no lights or accessories, set up for dirt only. I have looked high and low for a schematic of the internal wirings of a points magneto and it doesn't exist as far as I can tell. Common sense told me to disconnect the source coil from the lighting coil and when I did the points worked properly, when closed it's grounded and when they're open it's not. I checked the resistance of the source coil and got none with points open and 3.2 ohms with points closed. Also checked the lighting coil and got 1.4 ohms when static. When the engine turns it's erratic - 12, 24, 16, etc. I kicked it over again to check ac voltage and didn't show anything but as soon as I disconnect the negative lead on my meter I saw voltage dropping - 12, 8, 6 ,4 . Does anyone have any idea what my problem is? Thanks for any and all help.