Dooooogster Posted April 9, 2010 Share Posted April 9, 2010 Bought an early DT125R 1989 about a year ago as previous owner said that it cut out once on a journey and he hadn't looked at in 5 years. Hmmmmm..... Anyway, decided to restore this beauty back to its original glory as well as get me my bike license. Good intentions. This bike has been a labour of love & cost me a fortune! Smokie engine so replaced the worn old engine with a de-restricted mint one. However, after the engine warms up and is put through paces, it cuts out again. so replaced HT lead. Still cut out. The bike starts and idles fine, but when its ridden for a few miles, the engine bogs down ( you can hear and feel it going flat) and cuts out. As if when it gets up to almost correct temperature / going up a hill, it cuts out. It starts again staight away, but will cut out shortly after when putting demands on the engine. I need to leave it for 10 mins before I can at least get another few miles out it before it cuts out again. Journeys take ages and taking your bike for a walk isn't cool!! (Had a few car drivers stop, tell me they are bikers and offer me fuel to get home - the biking community is the best!) After messing about with jets on the old carb, I eventually got a replacement carb, replacement CDI unit and replacement regulator. Thought I had solved it, but hey, same old bog down and cut out. So after all the hassle the thing still cuts out. Checked fuel cap and cleaned air valves to make sure it wasn't a fuel vacuum problem, still cuts out. There is a strong smell of fuel just after it cuts out. Conclusion (it has to be?!). Worn or old wires to the HT leads. I recon if the wires on the loom are old and with the resistance of extra load at high revs or when the wires heat up, etc then it has to be that that cuts the current to the ht lead and the spark plug? Hence the smell of unused fuel from the engine? Any ideas how to fix this without replacing the entire loom? Am I on the right track? Have replaced everything else, so has to be the electrics surely? Any advice help, before i spend more time / effort / cash on another dead end? Link to comment Share on other sites More sharing options...
Paulwhite Posted April 9, 2010 Share Posted April 9, 2010 it dus sound electrical just check your connections to make sure there clean also make sure the terminals on ur battery are clean and on tight, is the loom earthing anywhere it shouldnt be? just giv it a good going over and hopefully u can find the problem. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 9, 2010 Moderator Share Posted April 9, 2010 My guess is either spark plug, ignition coil or pulser coil are faulty. Try a new plug first as its cheap and easy. Link to comment Share on other sites More sharing options...
Dooooogster Posted April 9, 2010 Author Share Posted April 9, 2010 My guess is either spark plug, ignition coil or pulser coil are faulty. Try a new plug first as its cheap and easy. Thanks for the tips. Forgot to mention that the 1st thing I did was replace the spark plug to one of these titanium plugs. Recon it must be one of the coils or an earth, or probably the worst of the lot a poor wire somewhere in the loom. I'll just have to work down the checklist. Thanks again. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted April 9, 2010 Moderator Share Posted April 9, 2010 Thanks for the tips. Forgot to mention that the 1st thing I did was replace the spark plug to one of these titanium plugs. Recon it must be one of the coils or an earth, or probably the worst of the lot a poor wire somewhere in the loom. I'll just have to work down the checklist. Thanks again. if you can...measure the resistance of the ignition coil both primary (LT) and secondary (HT) sides and make a note of the readings. Then when it cuts out repeat the test to see if it has gone open circuit. Repeat for pulse coil. Link to comment Share on other sites More sharing options...
Dooooogster Posted April 16, 2010 Author Share Posted April 16, 2010 if you can...measure the resistance of the ignition coil both primary (LT) and secondary (HT) sides and make a note of the readings. Then when it cuts out repeat the test to see if it has gone open circuit. Repeat for pulse coil. Replaced the coil and ht lead as well early on, so not that- but checked just incase i have been really unlucky. I am now working my way through the wire harness (the wires are 21 years old, so are black inside and hard to solder!). It is the last thing it can be. I'm not sure what other options i have got other than replace a few wires, as I doubt i would get a replacement 1989 dt wire harness. I'm guessing that the newer versions will be different anyway. Does anybody know if a newer (say 2004 DT) wire harness can be used for an older bike? - I accept some connection cutting and lots of soldering! Or have things changed beyond all recognition? I HATE electrics, would much prefer a mechanical problem......them I can solve! Link to comment Share on other sites More sharing options...
2 Wheels Posted April 16, 2010 Share Posted April 16, 2010 I HATE electrics, would much prefer a mechanical problem......them I can solve! You and me mate, i no like the electrics at all. OGit tests are the way to go me is thinking ! Also on very rare ocasions the HT lead can seem to work fine when it is checked at idle revs, but when the bike is out on the road and the revs are up the HT lead can brake down and miss, then when your back home and check it again it sems fine Dont ask me what happens to cause this but it can happen ! Maby its something to do with what OGit is saying about having an open circuit. Hope you get it sorted Link to comment Share on other sites More sharing options...
Deeteemx Posted April 16, 2010 Share Posted April 16, 2010 Replaced the coil and ht lead as well early on, so not that- but checked just incase i have been really unlucky. I am now working my way through the wire harness (the wires are 21 years old, so are black inside and hard to solder!). It is the last thing it can be. I'm not sure what other options i have got other than replace a few wires, as I doubt i would get a replacement 1989 dt wire harness. I'm guessing that the newer versions will be different anyway. Does anybody know if a newer (say 2004 DT) wire harness can be used for an older bike? - I accept some connection cutting and lots of soldering! Or have things changed beyond all recognition? I HATE electrics, would much prefer a mechanical problem......them I can solve! It should be easy to find whether the problem is electrical - simply take out the spark plug when the engine has cut out and see if it has a spark. As OG says, you can take readings for the 2 coils behind the flywheel (on the engine) with a multimeter and compare them with the resistances shown in the Haynes manual. The wiring loom is unlikely to be the problem as the ignition system bypasses most of it. The wires from the stator plate connect almost directly to the CDI. A loom from a post 1998 DTR is completely different....and loose connections on your battery will not affect the running of the engine. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 17, 2010 Moderator Share Posted April 17, 2010 It should be easy to find whether the problem is electrical - simply take out the spark plug when the engine has cut out and see if it has a spark. As OG says, you can take readings for the 2 coils behind the flywheel (on the engine) with a multimeter and compare them with the resistances shown in the Haynes manual. The wiring loom is unlikely to be the problem as the ignition system bypasses most of it. The wires from the stator plate connect almost directly to the CDI. A loom from a post 1998 DTR is completely different....and loose connections on your battery will not affect the running of the engine. Coming in at a completely different angle here, have you checked the oil pump is working OK? To me this sounds like the engine going tight. It could be delivering short quantities at higher rpm. Causing the piston to pinch slightly at higher rpm. I'm happy to be proved wrong but if the electrics are messing about cos they are getting hot they dont normally fire straight up after its cut out, you have to wait a bit first. Link to comment Share on other sites More sharing options...
Dooooogster Posted April 17, 2010 Author Share Posted April 17, 2010 Coming in at a completely different angle here, have you checked the oil pump is working OK? To me this sounds like the engine going tight. It could be delivering short quantities at higher rpm. Causing the piston to pinch slightly at higher rpm. I'm happy to be proved wrong but if the electrics are messing about cos they are getting hot they dont normally fire straight up after its cut out, you have to wait a bit first. Thanks for the fresh angles. When I say fires up straight away, not strictly true, I do have to give it a minute or two first. I have tried to start it immediately and it reacts like it is gassed, smell of fuel too. So far I have found that the negative wire to the battery had a screw in connector on it (clear plastic wire connector with the two counter-sunk screws on the top) which I have removed and soldered (please be that!). In addition I have removed the in-line fuse on the positive wire (maybe not such a great idea, but I need to find the problem!). Not tested it on the road yet, but the lights on the dash appear to be a lot brighter. I'll not get my hopes up, just in case........with this bike i'm cynical! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 18, 2010 Moderator Share Posted April 18, 2010 with this bike i'm cynical! Hang on!! :lol: Link to comment Share on other sites More sharing options...
NoTimeToPlay Posted April 18, 2010 Share Posted April 18, 2010 Bought an early DT125R 1989 about a year ago as previous owner said that it cut out once on a journey and he hadn't looked at in 5 years. Hmmmmm..... Anyway, decided to restore this beauty back to its original glory as well as get me my bike license. Good intentions. This bike has been a labour of love & cost me a fortune! Smokie engine so replaced the worn old engine with a de-restricted mint one. However, after the engine warms up and is put through paces, it cuts out again. so replaced HT lead. Still cut out. The bike starts and idles fine, but when its ridden for a few miles, the engine bogs down ( you can hear and feel it going flat) and cuts out. As if when it gets up to almost correct temperature / going up a hill, it cuts out. It starts again staight away, but will cut out shortly after when putting demands on the engine. I need to leave it for 10 mins before I can at least get another few miles out it before it cuts out again. Journeys take ages and taking your bike for a walk isn't cool!! (Had a few car drivers stop, tell me they are bikers and offer me fuel to get home - the biking community is the best!) After messing about with jets on the old carb, I eventually got a replacement carb, replacement CDI unit and replacement regulator. Thought I had solved it, but hey, same old bog down and cut out. So after all the hassle the thing still cuts out. Checked fuel cap and cleaned air valves to make sure it wasn't a fuel vacuum problem, still cuts out. There is a strong smell of fuel just after it cuts out. Conclusion (it has to be?!). Worn or old wires to the HT leads. I recon if the wires on the loom are old and with the resistance of extra load at high revs or when the wires heat up, etc then it has to be that that cuts the current to the ht lead and the spark plug? Hence the smell of unused fuel from the engine? Any ideas how to fix this without replacing the entire loom? Am I on the right track? Have replaced everything else, so has to be the electrics surely? Any advice help, before i spend more time / effort / cash on another dead end? I had similar symptoms with my XJ600 and spent ages not finding electrical problems. I had also checked the fuel cap vent (so I thought) but therein actually was the problem. The cap has a diaphragm valve (maybe a safety seal in the event of a fall?) I winkled out the diaphragm and have never had this problem since. Link to comment Share on other sites More sharing options...
Dooooogster Posted April 20, 2010 Author Share Posted April 20, 2010 I had similar symptoms with my XJ600 and spent ages not finding electrical problems. I had also checked the fuel cap vent (so I thought) but therein actually was the problem. The cap has a diaphragm valve (maybe a safety seal in the event of a fall?) I winkled out the diaphragm and have never had this problem since. Ok, winkled out the ballbearing and punched a hole in the other sponge hole to make sure that it is not the fuel cap vent. Bike awaiting a test run with the wee electrical fixes and petrol cap mod! I'll let you know if the mystery has been solved. Link to comment Share on other sites More sharing options...
dtre2006 Posted June 15, 2010 Share Posted June 15, 2010 hi my yamaha dt 125re 2006 bike cuts out after 65mph used to do 75mph but i have just noticed i have a hole screw in my carb next to my fuel pipe looks like a screw used to be there and now isnt , if anyone could no what needs to be there would be great help thanks Link to comment Share on other sites More sharing options...
Vez Posted June 15, 2010 Share Posted June 15, 2010 i give up! Link to comment Share on other sites More sharing options...
profscooter Posted June 29, 2010 Share Posted June 29, 2010 hi my yamaha dt 125re 2006 bike cuts out after 65mph used to do 75mph but i have just noticed i have a hole screw in my carb next to my fuel pipe looks like a screw used to be there and now isnt , if anyone could no what needs to be there would be great help thanks It's meant to be like that. Link to comment Share on other sites More sharing options...
profscooter Posted July 19, 2010 Share Posted July 19, 2010 When i got my first Dt i thought the same thing, it's meant to be like that so don't worry. hi my yamaha dt 125re 2006 bike cuts out after 65mph used to do 75mph but i have just noticed i have a hole screw in my carb next to my fuel pipe looks like a screw used to be there and now isnt , if anyone could no what needs to be there would be great help thanks Link to comment Share on other sites More sharing options...
Dooooogster Posted July 22, 2010 Author Share Posted July 22, 2010 ok, bike still cuts out, has been lying in the garage for a good few months, so now going to try again! About to throw in the towel and take it to a mechanic, although at £50 per hour labour (ouch!) could well end up the most expensive 1989 DT125 in the UK! Think the Spark plug cuts out when the engine warms up, although questioning my own sanity at the mo. Although I have renewed the coil and ht lead, still same problem occurs as the old coil and ht lead. Biggest mystery - when it heats up the engine eventually bogs down and cuts out (usually going up a hill). Plenty of blue smoke when it starts up then disappears so not an oil problem (unless the exhaust is clogged up with oil but i doubt it) Anybody know what wires connect to the HT lead and where the current comes from - and what theproblem could be? When it does cut out, i pull the spark plug out and it seems like no spark for a few kicks, then the spark reappears. How the mechanics are going to test this without taking it for a 15 minute ride - i don't know. This must be the most annoying problem ... For a laugh here is what i have replaced with this problem since I bought the bike (yes i am mental - although the bike is a lot sweeter, but same problem!) -Engine - top and bottom, -carb (x3) -ht lead and coil - regulator - cdi unit - petrol tank & cap - spark plug - battery - leads from the battery so the prob is with none of them! Link to comment Share on other sites More sharing options...
Moderator Airhead Posted July 22, 2010 Moderator Share Posted July 22, 2010 It could be a coil in the magneto or the pulser coil going open circuit when the engine gets hot. There will be tests to measure the resistance of these things so if you learn how to do that and then test when it cuts out you may find the faulty item. Link to comment Share on other sites More sharing options...
Dooooogster Posted July 23, 2010 Author Share Posted July 23, 2010 Thanks for the suggestion. It would just be my luck that the same problem would happen in the replaced magneto that was happening in the old magneto (i replaced the whole engine). I'll solve this mystery (prob via a professional mechanic) and I'll post the answer here. Stay tuned! Cheers. Link to comment Share on other sites More sharing options...
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