Ray1922 Posted March 6, 2010 Share Posted March 6, 2010 Hi, I have a 1991 DT 50 MX which will not spark at the plug. I have gone through all the usual checks, coil resistance, plug, all connections, magneto resistance, ignition switch, sidestand switch, kill switch etc. it is the CDI version ignition, and I am thinking that maybe that is the culprit. The bike was starting and running fine, then it would just cut out, then start straight away after. Now it will not spark at all, any ideas anyone? Thanks in anticipation Ray Link to comment Share on other sites More sharing options...
wild foamy Posted March 6, 2010 Share Posted March 6, 2010 wouldnt hurt to try a new CDI, theres usually some going cheap on ebay Link to comment Share on other sites More sharing options...
Ray1922 Posted March 6, 2010 Author Share Posted March 6, 2010 I can only find used ones, is there any way of testing these CDI's? Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 6, 2010 Moderator Share Posted March 6, 2010 Disconnect the keyswitch and try again Link to comment Share on other sites More sharing options...
Ray1922 Posted March 6, 2010 Author Share Posted March 6, 2010 Hi, The ignition switch is brand new, and seams to be working fine, however I do know that even new electrical components especially poorly constructed ones like this can be faulty. What is the theory behind disconnecting it then trying again? Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 6, 2010 Moderator Share Posted March 6, 2010 No the theory is to disconnect it and then try while it is disconnected, your bike has flywheel magneto ignition, when the key is off the signal is shorted to ground. also if switch faulty the signal can be shorted to ground, so it is an easy one to eliminate especially as you have checked many other things. Link to comment Share on other sites More sharing options...
Ray1922 Posted March 6, 2010 Author Share Posted March 6, 2010 Ok thanks will try that tomorrow. Ray Link to comment Share on other sites More sharing options...
Ray1922 Posted March 7, 2010 Author Share Posted March 7, 2010 Ok, tried disconnecting the ignition switch, still no spark, disconnected the kill switch no spark, disconnected the sidestand switch,no spark, plug sparks ok in another engine so plug looks ok. Anything I am missing here? Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 7, 2010 Moderator Share Posted March 7, 2010 Ok, tried disconnecting the ignition switch, still no spark, disconnected the kill switch no spark, disconnected the sidestand switch,no spark, plug sparks ok in another engine so plug looks ok. Anything I am missing here? Ray Disconnecting the sidestand switch is never going to give a spark, when the stand is down the switch is open and if put in gear with engine running will cut the spark then, usually only a problem when in gear these things. How did you check the coil resistance? what points did you take the measurement from? if the answer is from the LT wire to the coil laminations just repeat this from the LT wire to the batter NEG terminal, this should be the same or you have a bad ground on the coil. Also has the flywheel rotor come loose and sheared the woodruf key? Link to comment Share on other sites More sharing options...
Ray1922 Posted March 7, 2010 Author Share Posted March 7, 2010 Hiya,Interesting what you say about the sidestand switch. At no time, due to wear I guess, does the cam on the sidestand press the little plunger on the switch mechanism, maybe this could be the problem. I thought that by disconnecting the switch at the plug on the upframe spar that it would render it useless ie, making the engine start wherever the sidestand was, am I wrong in this train of thought? As far as checking the coil resistance goes, I checked the LT wire the little orange one to the earthwires bolted to the coil body, and got a 1 ohm reading, which is about right according to the manual. The HT wire I checked again to the same earth this also checked to the specified resistance rating 5.9 kohms. Going back to the sidestand switch, should the sidestand cam depress the plunger when it is up or down? Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 7, 2010 Moderator Share Posted March 7, 2010 Hiya,Interesting what you say about the sidestand switch. At no time, due to wear I guess, does the cam on the sidestand press the little plunger on the switch mechanism, maybe this could be the problem. I thought that by disconnecting the switch at the plug on the upframe spar that it would render it useless ie, making the engine start wherever the sidestand was, am I wrong in this train of thought? As far as checking the coil resistance goes, I checked the LT wire the little orange one to the earthwires bolted to the coil body, and got a 1 ohm reading, which is about right according to the manual. The HT wire I checked again to the same earth this also checked to the specified resistance rating 5.9 kohms. Going back to the sidestand switch, should the sidestand cam depress the plunger when it is up or down? Ray The sidestand switch should depress the plunger when the stand is up (usually). Yes you are wrong in thinking to disconnect it will get you going. When things go wrong here the usual short term get you going fix is to unplug the switch and make a shorting piece of wire with a couple of crimps on to put back in place of the stand switch....However if there is a stand switch problem this should only occur when the bike is put into gear, therefore....have you also got a neutral light problem? Still check the coil back to batt neg, this will verify a good ground path. Link to comment Share on other sites More sharing options...
Ray1922 Posted March 7, 2010 Author Share Posted March 7, 2010 Ok, thanks for that will try again, as it happens the neutral light is out at present,so need to look at that, however it was working before I started pulling everything apart. This bike is actually my sons,I have a CBR600, so much easier to sort out. Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 7, 2010 Moderator Share Posted March 7, 2010 This bike is actually my sons,I have a CBR600, so much easier to sort out. Ray Maybe so...but the DT is a better bike The neutral light and the sidestand switch appear to be the problem. Shorting the stand switch will no doubt get you going even if you dont fix the neutral light but it's hardly convenient for your son, get them both fixed properly though asap then the youg un doesnt come unstuck by riding with the stand down! Link to comment Share on other sites More sharing options...
Ray1922 Posted March 8, 2010 Author Share Posted March 8, 2010 Hiya, Shorting the side stand switch did not produce a spark either, think thats all there is to check now, time for a gallon of unleaded and a match Ray Link to comment Share on other sites More sharing options...
Moderator Airhead Posted March 8, 2010 Moderator Share Posted March 8, 2010 Hiya, Shorting the side stand switch did not produce a spark either, think thats all there is to check now, time for a gallon of unleaded and a match Ray No dont short the switch, unplug the switch and short the plug / socket whatever where the switch was plugged into. Apologies if that's what you meant. Dont know how it affects it so you should get the neutral light working too. Link to comment Share on other sites More sharing options...
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