DeTour Posted July 20, 2010 Share Posted July 20, 2010 Hey i just bought a DT 175 locally for 140 bucks. It's missing quite a bit. Here's the quick run down list that i made. Oil Injection cap Mounting bolts Injection lines Rear Fender bolts Kick stand Left foot rest Rack bolts Ignition switch screws Shifter seal Kickstart seal Handle bar bolt Handle bar grips Brake lever Chain guard "Exhaust Guard" air box screws and filter Front shock seals flywheel cover screws So not all that bad. Also been trying to narrow down why i don't have spark. I just ordered a manual, and i'm already leaning towards points and condenser. I unplugged the kill switch, tried a few different plugs, wiggled every wire imaginable, filed the points a little, sprayed it out with electrosol and aired it out. Still nothing. But i took out the thing that the points and magnetos bolt to and ohmed around a little bit. Someone made quite the mess of one of the magnetos by soldering wires to the coil. Alot of wires are just barely holding on, but i'm still getting fairly low resistance, like .9 or 1 ohm. A few questions, what should have what resistance, where. Also there's a diode looking thing with an arrow pointing away from the flywheel that has a black wire going to it. What should the resistance on that be. These old bikes always confuse me. But i want to know what i'm looking for when i sit there staring at it with meter leads in my hands. I"ll post up some pics if anyones interested. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 20, 2010 Moderator Share Posted July 20, 2010 Hey i just bought a DT 175 locally for 140 bucks. It's missing quite a bit. Here's the quick run down list that i made. Oil Injection cap Mounting bolts Injection lines Rear Fender bolts Kick stand Left foot rest Rack bolts Ignition switch screws Shifter seal Kickstart seal Handle bar bolt Handle bar grips Brake lever Chain guard "Exhaust Guard" air box screws and filter Front shock seals flywheel cover screws So not all that bad. Also been trying to narrow down why i don't have spark. I just ordered a manual, and i'm already leaning towards points and condenser. I unplugged the kill switch, tried a few different plugs, wiggled every wire imaginable, filed the points a little, sprayed it out with electrosol and aired it out. Still nothing. But i took out the thing that the points and magnetos bolt to and ohmed around a little bit. Someone made quite the mess of one of the magnetos by soldering wires to the coil. Alot of wires are just barely holding on, but i'm still getting fairly low resistance, like .9 or 1 ohm. A few questions, what should have what resistance, where. Also there's a diode looking thing with an arrow pointing away from the flywheel that has a black wire going to it. What should the resistance on that be. These old bikes always confuse me. But i want to know what i'm looking for when i sit there staring at it with meter leads in my hands. I"ll post up some pics if anyones interested. Whoa you got a bit to do there. I think the diode looking thing you are looking at is the condenser, which confusingly is actually just a capasitor. It acts like a baffle to prevent sparking at the points but if it fails it will kill the spark stone dead, ALWAYS replace it when you change the points. As to the coils a picture will be most helpfull as there are a couple of diffent modles with slightly different colours, it doesent vary much but it could really screw your results up for the sake of being certain. Also, in your next post. Please introduce yourself We don't bite, well not hard anyway........ Link to comment Share on other sites More sharing options...
DeTour Posted July 21, 2010 Author Share Posted July 21, 2010 Your right, i don't know if you mean open a new topic or just introduce myself here. None the less not meaning to be rude. I'm rob, live in massachusettes. I haven't been riding that long. I just turned 24, well today and have only owned one bike before buying this yamaha, which was the 76' ts 125. I went to college for auto mechanics through the asset program, so know a little about a little. I dig the old vintage bikes, cars, watches, guitars, drums, anything. I don't like new stuff, because i'm cheap. I joined a bike forum mainly for information, if i gain a few friends along the way, fantastic. I want to learn about things that i own, or things that i want to own as well as possibly contribute whatever it is i have experience with. So now that that's over and done with, I got a manual coming in the mail as well as points and condensor. I know this is noob stuff, but that doesn't make it any less confusing ha ha. Either way, i ohmed out from the coil to the Kill switch and got 1 ohm. Then from the key switch to the harness that connects to the flywheel 4.? ohms. I'm not sure what it should be, but i didn't think that from the key switch should be dropping resistance. Might be my problem. I"m going to take it apart tomorrow and see whats up. Here's the picture of the magneto i was talking about with all the solder. And the bike itself. this is that funky diode looking thing i can't seem to figure out. Open one way, 500 ohms the other Well that's all for now. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 21, 2010 Moderator Share Posted July 21, 2010 HA no i didnt mean open a new topic its just there has been a raft of one posters turning up recently and it gets a bit tedious as they invariably ask the same stuff. This one of yours is a bit different but its nice to have a bit of background to flesh out the bones if you like. And you never know there may be someone just round the block in the same boat. I have been to members houses to help them out with parts or info. Last one was a 100mile round trip. Looks a tidy bike, the later front muddy looks a little odd though, and the solderd coil don't fancy your chances of that being much good). The hear from the solder will have done the insulation all over the place. If we are talking 74 that will be a DT175A frame/chassis number 433-000101 onwards For that the coil res are as follows:- Ignition source coil 2.1ohm Primary ig coil 1.7ohm Secondary ig coil 6.0ohm Plug is a NGK B8ES or equivalent gapped at 0.02 to 0.024in with a 5Kohm resisted cap. Should help to get her running. Oh the funky diode thing is in the charging circuit to stop the battery copping ac voltage that they are none too keen on, it makes sure the battery gets a rudimentary form of DC to charge it. Link to comment Share on other sites More sharing options...
DeTour Posted July 23, 2010 Author Share Posted July 23, 2010 Just wondering if i'm chasing my tail here. But the p.o. decided it was a good idea to cut the kill switch wire in half and then twist the wires together. when i pulled the two apart while trying to find some spark and ohmed out the wire not attached to the switch to ground i find continuity. I have the connector going to the magneto unplugged. I had some really high resistance, then i unplugged the connector to the speedo and it dropped to .7ohms. At first, i un bolted the ignition coil and tested the wire that bolts onto the mount to ground and kept getting resistance to the frame. I unplugged every wire one at a time to try and detect a change and didn't find anything. Should I or should I not be finding resistance on that kill switch wire to ground? Finding resistance just didn't seem right, unless i'm missing something. How does the kill switch actually work? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 23, 2010 Moderator Share Posted July 23, 2010 Just wondering if i'm chasing my tail here. But the p.o. decided it was a good idea to cut the kill switch wire in half and then twist the wires together. when i pulled the two apart while trying to find some spark and ohmed out the wire not attached to the switch to ground i find continuity. I have the connector going to the magneto unplugged. I had some really high resistance, then i unplugged the connector to the speedo and it dropped to .7ohms. At first, i un bolted the ignition coil and tested the wire that bolts onto the mount to ground and kept getting resistance to the frame. I unplugged every wire one at a time to try and detect a change and didn't find anything. Should I or should I not be finding resistance on that kill switch wire to ground? Finding resistance just didn't seem right, unless i'm missing something. How does the kill switch actually work? Pretty much what happens with your ignition is...... The ignition sourse coil generates the primary voltage, i will emphasise the battery has NOTHING to do with ignition. This passes to the points and condenser. The condeser stores excess voltage and releases it when the points close. If the condesers fail they allow the ig voltage to drop to earth and kills the spark. From here it will travel to the ignition coil, the kill switch and obviously the ignition. If the kill switch is connected to ground the electricity being naturally lazy will take the easy way to ground. This naturally means no electric passing through the ig coil and so no spark. With the kill switch not grounding the circuit the electric will subsequently pass into the ig coil and generate the secondary high voltage to supply the spark. Link to comment Share on other sites More sharing options...
DeTour Posted July 23, 2010 Author Share Posted July 23, 2010 something just doesn't seem right with this wiring. I drew up a quick scheme of what my ignition wires are doing. Past this point, i'm not sure what the black wire does. But it almost seems like my kill switch is in the wrong spot. Continuity checks just don't seem right. But i keep getting real low resistance to ground at the kill switch wire with it disconnected. I'm just scratching my head here. Don't know if i'm looking for the wrong problem and i don't wanna dig too too far, even though just about all the electrical tape is off already ha ha. The clymers manual doesn't seem to have alot on this particular bike. Any chance someone would know of a better one, and where i could find it? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 24, 2010 Moderator Share Posted July 24, 2010 Here is a nasty diagram typical of the early seventies, it is not clear and all that accurate either. DT 175 A diagram This is a much clearer diagram for the DT175C which is practically the same as yours. DT 175 B/C (1975) Diagram If the wiring isn't the same it will be very close. As in near enough to work from. There are small links and odd connections that sneak in that aren't on the main drawings so some common sence is needed on the older stuff. When i rewired my 175 there was quite a few extras i didn't realise i needed till i picked the old loom apart one wire at a time. Hope this helps. Diagrams thanks to Dewpy's link in the workshop section Link to comment Share on other sites More sharing options...
DeTour Posted July 24, 2010 Author Share Posted July 24, 2010 That bottom diagram really clarifies things. It looks like everything is good. I can unplug the tach, speedo, and lights. The only thing that i haven't found in any diagram or book is that diode/condensor thing. I'm running without a battery so can i just eliminate that. Were these old bikes meant to run with a battery? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 24, 2010 Moderator Share Posted July 24, 2010 I can unplug the tach, speedo, and lights. The only thing that i haven't found in any diagram or book is that diode/condensor thing. isnt the diode item 15 in the diagram? Like Cynic said earlier it's a half wave rectifier to charge the battery. I'm running without a battery so can i just eliminate that. Were these old bikes meant to run with a battery? The battery would supply lights (except headlamp), instrument lights, brake lights, turn signals, horn to name but a few. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 24, 2010 Moderator Share Posted July 24, 2010 That bottom diagram really clarifies things. It looks like everything is good. I can unplug the tach, speedo, and lights. The only thing that i haven't found in any diagram or book is that diode/condensor thing. I'm running without a battery so can i just eliminate that. Were these old bikes meant to run with a battery? The funky diode thing is driving me nuts, it was on a while back from somebody else and for the life of me i can't recall what its for. Am i right (looking at the photo) that its in the black ig feed? No you dont need a battery, i take it she's going to be a bush basher then? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 24, 2010 Moderator Share Posted July 24, 2010 Kapow, in while i'm not looking OG Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 24, 2010 Moderator Share Posted July 24, 2010 The funky diode thing is driving me nuts, it was on a while back from somebody else and for the life of me i can't recall what its for. Am i right (looking at the photo) that its in the black ig feed? Sorry Cynic I may be barking up the wrong tree, this may be that other one you mentioned, I think it was decided in the other thread that it was called an avalanche diode (much the same as a zener) and would attempt to control the charging voltage. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 24, 2010 Moderator Share Posted July 24, 2010 Sorry Cynic I may be barking up the wrong tree, this may be that other one you mentioned, I think it was decided in the other thread that it was called an avalanche diode (much the same as a zener) and would attempt to control the charging voltage. Thats the puppy, so we can safely chuck that in the bin with all the other charging/lighting stuff. Link to comment Share on other sites More sharing options...
DeTour Posted July 25, 2010 Author Share Posted July 25, 2010 Thats the puppy, so we can safely chuck that in the bin with all the other charging/lighting stuff. ya that thing is inline with the ig feed wire from the stator. So i can just disconect it? Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 25, 2010 Moderator Share Posted July 25, 2010 ya that thing is inline with the ig feed wire from the stator. So i can just disconect it? OOOOH if its in the ig circuit then its more likely there to prevent a reflected signal from the coil upsetting things so i'd leave it there for now. The avalance diode was an early improvement on a big assed power resistor bolted to the frame to control the charging voltage for the battery/lights. But the important point here is that it was fitted in the charging circuit. Any nearer with getting her running? Link to comment Share on other sites More sharing options...
DeTour Posted July 27, 2010 Author Share Posted July 27, 2010 I'm just waiting on points and condensor to come in. I probed around the coils and the main ig coil. They seem fine. I gotta say thanks for having patience with me. I tend to blow 2 strokes out of proportion i think. If i install the points and condensor and get some spark, i'll find an air filter, clean the carb out and ride it til my hearts content. Link to comment Share on other sites More sharing options...
DeTour Posted August 1, 2010 Author Share Posted August 1, 2010 Well i got a few things coming for me. Still waiting on the points and condensor and i found a set of foot pegs and a few nuts and bolts from ebay. One other question is that someone disco'd the oil injection a while ago. Do i need to modify anything to run premix? I've heard stories about main bearings with other bikes. Will it be a problem on this one? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 1, 2010 Moderator Share Posted August 1, 2010 No all bearings will be fine, some people also say next larger jet too, it's up to you. Link to comment Share on other sites More sharing options...
DeTour Posted August 6, 2010 Author Share Posted August 6, 2010 I got the points and condenser in there, still no spark. I ohmed the ignition coil between the plug wire and the base that bolts to the frame and get 11.6k ohms. Then between the plug wire and ig input and get the same reading. Then between the input and the frame base i get 2.2 ohms. So it looks like the primary is a little high, and the secondary is just about double the resistance that it should be. I guess i'll be ordering one of those too. ha ha... ugh. edit: anyone know a source for the ignition coil. Ebay had nothing, and bike bandit had nothing. I cross checked part numbers and i couldn't find anything else that matched. Link to comment Share on other sites More sharing options...
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