crowtoms Posted February 8, 2009 Share Posted February 8, 2009 I bought an old (1982/3) Yamaha DT125R at an auction sale as a non runner. It is very bare, no lights etc. and only suitable for off roading. It had NO SPARK.! stripped & cleaned electronics (Battery seems defunkt but should not matter) now getting a weak spark but wont fire, drained Tank & Carb and fuel seems to be getting to the head (plug is damp when inspected) Could it be a timing problem or mixture.? Getting frustrated cos these machines seem V. simple to operate.!!! Been trying again this afternoon when the plug is out & earthed there is intermintent spark, but put plug back in cylinder bump start.. nothin' could it be shorting out or something.? PLEASE HELP.! Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 If you are getting a spark, I would buy a new plug and drain and replace the fuel, also drain the fuel in the carb, then try again, maybe with a bump start if thats possible. Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 If you are getting a spark, I would buy a new plug and drain and replace the fuel, also drain the fuel in the carb, then try again, maybe with a bump start if thats possible. Tried all of those... for some reason the fuel is just not firing: there is a cut off switch on the bars but I dont know how this should be wired & wires leading to crank case are these important.. apart from this there is very little to go wrong with it.? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 Tried all of those... for some reason the fuel is just not firing: there is a cut off switch on the bars but I dont know how this should be wired & wires leading to crank case are these important.. apart from this there is very little to go wrong with it.? Are you not getting any attempt at all to fire, Im not familiar with your bike though, is it a kick start only, air cooled or water cooled? As far as i know , if you are getting a spark??? then the cut of switch must be OK, usually the cut off switches earth out the LT signal to the coil on these bikes, so you wouldnt get a spark if it was faulty. One thing to add here though is to check the side stand switch is either working properly or is by passed properly with nice clean connections. Link to comment Share on other sites More sharing options...
blackhat250 Posted February 8, 2009 Share Posted February 8, 2009 there is very little to go wrong with it.? ------------------- Now then Intermitent spark" i take it its a CDI [1982/3] . U HAVE CHECKED THE TIMING , ie Theres a pulser coil on back plate . and has to be time at the exact degree before T.D.C. . If this is correct . the its prob the CDI unit, Also remember the coil [ below tank . its maybe weak . U"l need a manual to set timing . coz there all slightly different [125/175/250/400] always check & renew the cheapest component first . Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 Are you not getting any attempt at all to fire, Im not familiar with your bike though, is it a kick start only, air cooled or water cooled? As far as i know , if you are getting a spark??? then the cut of switch must be OK, usually the cut off switches earth out the LT signal to the coil on these bikes, so you wouldnt get a spark if it was faulty. One thing to add here though is to check the side stand switch is either working properly or is by passed properly with nice clean connections. [/quote Air cooled. Kick Only Spark appears at plug BUT NO FIRE AT ALL..!! What is this side stand switch. not fimiliar with electronics..? Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 there is very little to go wrong with it.? ------------------- Now then Intermitent spark" i take it its a CDI [1982/3] . U HAVE CHECKED THE TIMING , ie Theres a pulser coil on back plate . and has to be time at the exact degree before T.D.C. . If this is correct . the its prob the CDI unit, Also remember the coil [ below tank . its maybe weak . U"l need a manual to set timing . coz there all slightly different [125/175/250/400] always check & renew the cheapest component first . Erk..! Whats the CDI Unit. there are no markings so I dont know what model it is, thus manual.?? I can send a pic if helps.. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 Air cooled. Kick Only Spark appears at plug BUT NO FIRE AT ALL..!! What is this side stand switch. not fimiliar with electronics..? Some bikes, almost all later than the 70's, have a side stand switch, this will stop the spark if put in gear with the stand down, I dont think you have that problem as you have seen it sparking A CDI is a 'Capacitor Discharge Ignition' its what the old points systems were replaced with, its an electronic black box gadget and either works or does'nt, your does...you have a spark Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 Are you not getting any attempt at all to fire, Im not familiar with your bike though, is it a kick start only, air cooled or water cooled? As far as i know , if you are getting a spark??? then the cut of switch must be OK, usually the cut off switches earth out the LT signal to the coil on these bikes, so you wouldnt get a spark if it was faulty. One thing to add here though is to check the side stand switch is either working properly or is by passed properly with nice clean connections. My bike seems to be the same model as yours (on your reply page) but smaller engine I can send pics if you like..? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 My bike seems to be the same model as yours (on your reply page) but smaller engine I can send pics if you like..? Tom your pics didnt arrive to my email!! to post pics do this Open a photobucket accountUpload your pics therewith each pic you will see four fieldsCopy the IMG fieldPaste into the forum Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 Cant seem to do it that way..? [email protected] post here & I can reply direct..? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 So this is it! its a DT175MX like mine, so long as the engine number begins with 2K4 Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 So this is it! its a DT175MX like mine, so long as the engine number begins with 2K4 Yeah.. Bit of a wreck Eh.? But worth getting going... Any th'wiser. I bought new plug and coil but for a DT 125 would this make any diff.? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 8, 2009 Moderator Share Posted February 8, 2009 Yeah.. Bit of a wreck Eh.? But worth getting going... Any th'wiser. I bought new plug and coil but for a DT 125 would this make any diff.? Dunno mate, but lets find out what you have first...what's the engine number?, we'll get it sorted in the end no doubt try to be patient. Also it will say the engine displacement in the casting of the barrel, it will say 171cc or i think 123cc Link to comment Share on other sites More sharing options...
crowtoms Posted February 8, 2009 Author Share Posted February 8, 2009 Dunno mate, but lets find out what you have first...what's the engine number?, we'll get it sorted in the end no doubt try to be patient. Also it will say the engine displacement in the casting of the barrel, it will say 171cc or i think 123cc OK.. Thanks very much for your help so far.. I will get an engine number and take some more detailed pics. thanx again Tom. Link to comment Share on other sites More sharing options...
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