jzacher85 Posted March 12, 2014 Share Posted March 12, 2014 Hello All, So I just got a DT 175 that has not been running for a year or two. When I got a hold of it the tank was very rusted so I cleaned and re-lined it. I put a new Carb on it. I have checked the Ignition coil and it passed. I found that I am not getting any power to the coil when kick starting it. I checked the charge and pulsar coils to factory specs. They were low ( around 360 when it called for 410) but it would seem I would get some spark from it. I was wondering any other tests I could do. I was thinking that perhaps the CDI unit has gone out. The other issue is that when I pulled the magnet housing off the crank shaft the woodruff key had sheered. Now I will of course be replacing this but had the question of if it would still spark if they crankshaft grooves were not aligned with the housing? Would something sense the timing is off and the CDI would not allow spark? Are there any tests I can do to the CDI unit to test? Thank you for any information. -Jesse Link to comment Share on other sites More sharing options...
Moderator Cynic Posted March 12, 2014 Moderator Share Posted March 12, 2014 Without a good woodruff key your wasting your time, there is a point on the mag that triggers the spark, exactly what isn't obvious but its in the construction of the rotor. If your out by 2 or 3 mm you will get nothing as far as starting the engine. Don't worry about the cdi, its little more than a glorified cigarette lighter, really basic and pretty much nuclear bomb proof. The DT generates its own spark energy, so, without a good kick you will get nothing from the ig. It has nothing to do with anything else either, not the battery, any voltage regulation its all in the mag coils. Mag spins, generates electric, that makes the cdi generate the coil feed to kick the spark. Very basic, very reliable. I have been very grateful for its simplicity in the past when the only thing left working on a trail was the engine. Link to comment Share on other sites More sharing options...
blackhat250 Posted March 12, 2014 Share Posted March 12, 2014 After you"ve got the timing / key issues fixed, disconnect the Black/white wires from kill switch and ignition. these ground the CDI, Should spark then. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 12, 2014 Moderator Share Posted March 12, 2014 yeah as cynic said it's a 'must do' to fit a new key. sheared keys are caused by not tightening the flywheel nut to the specified torque and so this is another 'must do'. let us know how you get on with this Link to comment Share on other sites More sharing options...
nayruf Posted March 13, 2014 Share Posted March 13, 2014 Hi When I had my first magneto rotor’d bike, (late 70's 'S' registered) the woodruff key would shear frequently, I had torque’d the nut up as dictated by the manual and the key would still shear. On investigation I realised that the key does not actually transmit drive from the shaft to the rotor, obvious I know but I was young and inexperienced, I am now old and stupid. So because of this the drive is transmitted to the rotor because the rotor is wedged on the taper of the crank shaft stub, similar to a ‘Lathe or pillar Drill ‘Morse taper mounted chuck’ that has a chuck wedged on its taper relying on the tapers to lock together, and has to be removed with a wedge drift of the correct size, to this end I noted that if the woodruff key sat high in its crank shaft location point and contacted with the slot in the magneto before the magneto fully seated on the taper on the shaft, even with the correct torque applied to the nut the key would shear periodically as the rotor skidded around the shaft, I was able to stop this happening, buy making sure the key was sitting low in its location and even dressed the key with a ‘Riffler’ file to achieve this, I also made sure the tapers in the magneto rotor and on the crank stub were scrupulously clean and free from any grit or debris that could prevent the tapers from locking together. Others may say this is a waste I am an arse and you can ignore this and 9 times out of 10 they could be right. But since 1978 to this day I have not had a key shear on my magneto since, Just a point to note, hope it may help, Link to comment Share on other sites More sharing options...
jzacher85 Posted March 13, 2014 Author Share Posted March 13, 2014 Thanks for the info! Can anyone tell me the size woodruff key I need? Link to comment Share on other sites More sharing options...
nayruf Posted March 13, 2014 Share Posted March 13, 2014 Thanks for the info! Can anyone tell me the size woodruff key I need? http://www.tytrials.co.uk/trailandtrialsuk/prod_387186-Woodruff-Key-Flywheel-Side-DT175.html Link to comment Share on other sites More sharing options...
jzacher85 Posted March 14, 2014 Author Share Posted March 14, 2014 ok, I got a woodruff key in and slid the magneto back on tried for spark and still got zero. A couple things when Cynic BANG! and the bulls.its gone says without a good kick I have been kick starting it with my hand ( it easily turns) and watching for spark. Should I be cranking on it hard with my foot instead? Also, when blackhat 250 says After you"ve got the timing / key issues fixed, disconnect the Black/white wires from kill switch and ignition. these ground the CDI, Should spark then. How do I do this w/o cutting the wires as the ignition wires come to behind the headlight and to a plug that has about 4-5 wires? Definitely getting a little frustrated! I pulled the Neutral switch and its brass nub looked quite worn. Maybe try depressing the clutch when kick starting to see spark? Any further help would be great! Thanks again for the help, Cheers, Jesse Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 14, 2014 Moderator Share Posted March 14, 2014 ok, I got a woodruff key in and slid the magneto back on tried for spark and still got zero. A couple things when Cynic BANG! and the bulls.its gone says I have been kick starting it with my hand ( it easily turns) and watching for spark. Should I be cranking on it hard with my foot instead? Yes its best to kick a little quicker, with your foot Link to comment Share on other sites More sharing options...
blackhat250 Posted March 14, 2014 Share Posted March 14, 2014 Just pull the whole connector apart, the other wires are for lights etc. they"re may be a separate bullet connector for kill switch on bar, Link to comment Share on other sites More sharing options...
Moderator Cynic Posted March 14, 2014 Moderator Share Posted March 14, 2014 Dont get carried away with overcomplicating things. A normal kick should give a nice bright blue spark. If not check all the basics. Plug plug connection coil coil connection the connector lhs of the carb lastly check the wiring hasnt touched the exhaust under the tank. Link to comment Share on other sites More sharing options...
jzacher85 Posted March 16, 2014 Author Share Posted March 16, 2014 Alright! Got spark. Pulled the b/w wire where it goes into a splice for a Y. Put the plug back in, tanks back on, and have been trying to start her with no luck! I bought a new carb for it. I did as the manual said and backed out 2.5 rotations from seated. Tried with and without choke. I am currently at 5,000 Feet in elevation. Any special settings for it? I have been trying to kick it, then pulling the plug and cranking w/o plug to clear it then installing plug and trying again. Tried several times. Any tricks or comments? THanks for the help. YOu all have been super helpful. -Jesse Link to comment Share on other sites More sharing options...
Moderator Cynic Posted March 16, 2014 Moderator Share Posted March 16, 2014 When you say bought a new carb.... Was that a proper carb, from a Dt? If it is a chineese copy (most of the brand new ones are) it may not work at all. The carb is like the electrics. Very reliable. Link to comment Share on other sites More sharing options...
jzacher85 Posted March 29, 2014 Author Share Posted March 29, 2014 Alright, I got her up and running. She has problems starting and on the lower end of the power band. It will try to die unless a decent amount of throttle is laid out before releasing the clutch in first gear. Now that I am able to start it and it runs (poorly) I need to get the lights to work. I assume that having unplugged the black/white ground wire for the CDI I cannot run the lights? What do I need to do to be able to run it with the black/white lead plugged in? Also, I am running pre-mix right now because my oiler is not working. I tried to prime it by opening the drain screw until it bled and then trying to fill the hose to the carb with some oil. Still will not push any oil. Thanks, JEsse Link to comment Share on other sites More sharing options...
jzacher85 Posted March 30, 2014 Author Share Posted March 30, 2014 any help? Link to comment Share on other sites More sharing options...
blackhat250 Posted March 30, 2014 Share Posted March 30, 2014 Right , the B/White wire only grounds the spark,[ fault must be on kill switch or ignition] = lights will work, Your poor running - could be High altitude, [ lack of air - poor mixture] = drop the needle a clip. smaller pilot maybe. The pump [oil] you"ve bled it, now when bikes on idle , pull the pump cable to full open [ not throttle cable] till oil rises to carb, [ clear hose to see this ] Link to comment Share on other sites More sharing options...
jzacher85 Posted March 31, 2014 Author Share Posted March 31, 2014 thanks for the tips. I will check into those items. She is soo close to being in great shape! Link to comment Share on other sites More sharing options...
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