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Old 09-23-2014, 05:43 AM   #1
Dingle OP
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Joined: Jul 2013
Oddometer: 20
Question Weird spark issue 640 LC4

Ok, so after a complete stripdown and rebuild of my '03 640 LC4 SM, I'm still having issues with the spark, this is what has been done.
-New coil, cap and plug
-New pulser coil
-checked/cleaned CDI and ignition switch contacts.
-Tested CDI to be delivering 200v to coil.
-Ground well connected. (bike turns over on estart)

stator looks good, wiring harness is showing a little wear, but no shorting. assuming the reg/reg to be sweet. never had battery issues when it was running.
Now, the KTM mechanics at work said, just replace everything till it works, which is a tad expensive.
up until i installed the new pulsar coil, when the plug cap was off it would give off a little spark, but when it was connected with a plug it wouldnt spark.
With the new pulsar coil i get absolutely nothing.
Havent tested the CDI output voltage since then.
Before I stripped the bike down for rebuild, the bike would cut out when hot and slowing down/idling.

Does anyone have the slightest as to what it might be and why so i dont have to buy the rest of the electrical system?
Please and thankyou.

If anyone can answer this correctly and save me the money, I might have some 640 goodies you can have ;)
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Old 09-23-2014, 06:09 AM   #2
kingrj
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Location: Hattiesburg, Mississippi
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Quote:
Originally Posted by Dingle View Post
Ok, so after a complete stripdown and rebuild of my '03 640 LC4 SM, I'm still having issues with the spark, this is what has been done.
-New coil, cap and plug
-New pulser coil
-checked/cleaned CDI and ignition switch contacts.
-Tested CDI to be delivering 200v to coil.
-Ground well connected. (bike turns over on estart)

stator looks good, wiring harness is showing a little wear, but no shorting. assuming the reg/reg to be sweet. never had battery issues when it was running.
Now, the KTM mechanics at work said, just replace everything till it works, which is a tad expensive.
up until i installed the new pulsar coil, when the plug cap was off it would give off a little spark, but when it was connected with a plug it wouldnt spark.
With the new pulsar coil i get absolutely nothing.
Havent tested the CDI output voltage since then.
Before I stripped the bike down for rebuild, the bike would cut out when hot and slowing down/idling.

Does anyone have the slightest as to what it might be and why so i dont have to buy the rest of the electrical system?
Please and thankyou.

If anyone can answer this correctly and save me the money, I might have some 640 goodies you can have ;)
My buddy had a similar isssue with his 640 recently and it turned out to be his stator. His stator had come loose and the rotor got into it causing some turn to turn shorts causing low output voltage from the stator. The issue was that in his 640 the power to the CDI does NOT come from the battery but it comes off one phase of the three phase stator coil. If you take a VOM and set it to AC you should be reading about 40-60 or so VAC on the two wires going from the stator to the CDI when the bike is cranking over. If not you will get a weak spark or no spark. I know you said your stator is fine but make sure the connections from the stator are good and you are getting 40-60 vac to the CDI when the bike is cranking over. Good luck!
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Old 09-23-2014, 06:38 AM   #3
Dingle OP
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Thanks! will test it out tomorrow, and let you know!
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Old 09-23-2014, 06:44 AM   #4
kingrj
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Thanks! will test it out tomorrow, and let you know!
After thinking about it a while more..I am pretty sure your stator output is the issue..The output from the stator is dependent on the engine rpm..the higher the rpm the higher the AC output of the stator so it makes sense that if it is cutting out at idle it is due to low AC going into the CDI. If that is not what it is then you got a bad CDI..but I don't think so...After we replaced my buddies stator all was OK...Anyway..a stator is about $110 and a CDI is waaaay more! I hope it is the stator!
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Old 09-24-2014, 01:31 AM   #5
Dingle OP
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Ok, so i checked the stator with the bike cranking off a jump pack, and tested all pins. With my multimeter set to 200 it read 00.7 which i would believe means 7v, and it was reading 3.5amps.
so, way off you reckon?
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Old 09-24-2014, 05:58 AM   #6
kingrj
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Originally Posted by Dingle View Post
Ok, so i checked the stator with the bike cranking off a jump pack, and tested all pins. With my multimeter set to 200 it read 00.7 which i would believe means 7v, and it was reading 3.5amps.
so, way off you reckon?
First off...if it was a digital volt meter set to AC..and it read 00.7 volts that is all you got! 0.7 VAC no matter what the upper scale was set to. And as this while it was still connected to the CDI or did you have the two wires disconnected from the CDI when you measured it? Disconnected you should have been able to measure 40-60 VAC. When you indicated it was reading 3.5 amps..did you have the VOM set for amps and did you have it inserted in series between the CDI and one of the stator lines when you measured this? If so that is waaaaaay off! The CDI should never have pulled as much as 3.5 amps! Make sure you disconnect the two wires running from the stator to the CDI and measure the voltage on those two wires while cranking it over and see what the voltage is. I am sorry I was not more specific in my earlier post, I am an electrical engineer and I take stuff for granted some times! It sounds to me like you are getting NO output from your stator on the two wires going to the CDI....OR the CDI is shorted out. Run the test again as indicated with wires disconnected and let's see..that should tell us. I love working on problems like this..especially if i am not the guy with the problem!
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Old 09-25-2014, 01:38 AM   #7
Dingle OP
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haha.
I only measured across the 3 output pins of the stator while it was disconnected, all pins giving me the same result. will have to try it with it hooked up. Thanks for your help man!
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Old 09-25-2014, 05:54 AM   #8
kingrj
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haha.
I only measured across the 3 output pins of the stator while it was disconnected, all pins giving me the same result. will have to try it with it hooked up. Thanks for your help man!

Awesome! Then you are in luck! The stator is fried and your expensive CDI is probably fine! ElectroSport sells stators for about $120 for that bike. That is what my buddy put in his. Good luck!
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