13 replies to this topic

[dsm6678]

I keep blowing out headlight and taillight. I put a regulator in but no help. I am getting very strange readings from the ac meter. I am actually getting readings off the engine and frame of the motorcycle of 12v to 19 volts and it is jumping around like crazy between that voltage. I unpluged the regulator from the motorcycle but it was still bolted to it and i am getting voltage comming out of the regulator unplugged BECASUE there is voltage running through the frame.

Anyone have any idea why there would be current running thought the engine and frame? I even tested the ground wire comming out of the headlight and it has 12v to 19 v comming out of it (engine running) but the headlight will work until I drive it up the road then it blows.

Lighting coil bad?

Please help

Darren

Edited by dsm6678, 13 December 2011 - 06:36 AM.

[feetupfun]

Its hard to tell from what you have written, but it sounds like you might be measuring voltages of open circuits. If the ground wire in the headlight circuit is 19V above the frame voltage, then the "ground" wire is not grounded. To find out what voltage the bulbs are seeing at different RPM, measure the voltage difference between supply and ground with the headlight and taillight both on.
Some bikes do make too much voltage at high revs even with the correct bulbs in service and good earths. I used to use 12 and 24 volt bulbs in my (nominally 6 volt) 1970s Japanese trials bikes and trail bikes to avoid blowing bulbs. I have seen many other techniques successfully used too.

[Dadof2]

Sounds like it should have some form of zenner diode to limit the voltage. This would be on the live feed from the lighting coil.
Have a word with Rex Caunt racing.
Cheers

[dgraf]

kinda going out on a limb.......but if the ignition switch is still being used,check it out also,can lose the ground and cause headlight to be on,but not burning at full brillance
until bike is revved up then light starts really burning bright!..... of course that was after finding out nothing was wrong with headlight or the rectifier.....sigh. hope this helps.

[dsm6678]

Thanks for everybody getting back to me. I appreciate the help!

Anyway it is strange it is getting 12-19 volts at idle and when I rev it up same voltage readings. I have checked all grounds and the grounds in the stator also and they seem good. WellI am going to clean off the rest of the ground connections and stator plate and then I was thinking of removing the lighting coil to see if the volts dissappear from the frame and engine metal (motorcycle running). If they do then I am thinking if possibly the coil wire on the lighting coil is touching the iron core causing a short to ground.???

If that is the case I will recoil the lighting coil with the correct size mag wire and count the turns of wire to get the correct resistance.

Any other suggestions would be appreciated

[Hekto]

First of all - a zener diode can not solve the problem. It should handle alle the current when voltage comes over 12 Volts.

You have to check all the wiring and especially the grounding wires and connections.

Systems with 'light coils' are normally not regulated. The voltage (AND frequency) variates with RPM's (naturally). You therefore have to be sure that your meter can handle the frequency to get the correct values when you meassure.

Start to meassure close to the wires comming from the engine. Then measure the voltage on the wire feeding the electrics still holding the refference to the engine case. Measuring any voltage across groundings or gound wires (say about 1 Volt) indicates brocken wires or bad connections.

[dsm6678]

Ok here is where I'm at.... Checked ground connections again everything seems good. I wire brushed the stator plate to make sure it is grounded. I wire brushed a sad looking ground wire on the cdi box. I also sanded the coils and magnets (removed the rust). I had already cleaned out most of the electrical connections before I started it just to be safe. I studied the wireing diagram and checked conncetions with an ohm meter and they seem good I still have voltage flying through the engine cases and frame and that should not be. I thought that the rust in the magneto was causing a short but i guess not.

Well tomorrow I am thinking I will remove the lighting coil and then start the motorcyle and see if I am still getting voltage thoughout the motorcycle metel casings. Do you think this is a good test or am i missing something?

Thanks, Darren

Edited by dsm6678, 15 December 2011 - 05:39 AM.

[feetupfun]

I suggest you first measure the voltage difference between the motor casings and the frame. If there is a voltage difference, then your motor is not grounded to the frame (and it needs to be grounded to the frame)

[dsm6678]

Ok I took a really close look at the stator and I noticed that the "pulser coil" looks like it has overheated. The wrap around it has turned black and looked a little melted. Now the pulsar coil is attached to another "coil" in the stator here;

http://www.kawasakip...i/KT250-A_(1975)/IGNITION%2f%2fGENERATOR/KT250-A-1975/070092B-14

and it is just called "coil" on the kawasaki parts diagram. I checked the resistance for those coil"s" and I am getting about 31 ohms. While I had the ohm meter connected between the wiring on those coils I put pressure on the burned up looking one with my fingers and the resistance was changeing to a lower reading. I think that it confirms that the (outer) coil pulsar is damaged and has a short (wire coating burned and causing a lower resistance). The other coil it is attached to in the stator looks good so I am guessing that is why the motorcycle still runs but I am guessing it is not getting the best spark since the smaller (outer) coil is comprimised.

Now I wonder if that is causing "stray voltage" running throught the motorcycle?

I have gone OVER EVERYTHING and found a few damaged wires and fixed them but still have the problem. Checked all grounds and checked if any power wires where touching ground and found no issues. I cleaned all grounds for the stator.

I guess I have to fix this pulsar coil anyway and I am betting that this is the source of the stray voltage running through the motorcycle but I could be wrong.

What do you guys think of melted insulation on a pulsar coil with low resistance causing stray voltage?

I am thinking with the 31 ohms of resistance the bike can still run but with problems. I wish the service manual would give a spec on the resistance for the coils but it does not. I know my yamaha dt 400 has 90 ohm's of resistance but that is a much different looking pulsar coil.

Anyway I am sure the pulsar coil has partially failed but I wonder if it is part of the stray voltage problem. I guess I will take it apart get the wire size, count the turns and recoil it with mag wire and put that wrap around it and see what happens. This is a tough one. Any suggestions would be nice thanks.

P.S. Anybody know why there are two pickup coils connected to one another instead of just one "big coil" one on this motorcycle?

[dsm6678]

Hello! I wanted to update the problem with the kt 250 blowing lights. I rewound the pulsar coil with 34 guage mag wire to the oem width since it was damaged (insulation black, wire insulation damaged and resistance moving around when I touched it with my fingers). I took some pictures but some are not high quality I wanted to show you. I used the correct 3m # 12 tape for the inside wrap (very hard to get unless you by a case of it). The sales rep from 3m for the east coast (U.S) was nice enough to send me two sample rolls (different widths). I also used the correct cloth tape and varnish for the outsied wrap. Well my spark looks REALLY GOOD now but I STILL HAVE STRAY VOLTAGE RUNNING THROUGH THE MOTORCYCLE. Hmmmmmmmm.........

I really have to think for awhile about this one!!! Unless someone has any ideas on what would cause that to happen. I have to fnd the problem!! help.

Hey how do I upload pictures to this site?

[dsm6678]

Update to the electrical problem (blowing lights out on kt 250)

I took the main spark plug out or the one currently being used (there are two of them in the head different heat ranges i guess for different environments) and the problem of voltages running throughout the bike dissappeared. Well I decided to try the other spark plug. THE PROBLEM IS ELIMINATED. Looks like the spark plug is malfunctioning (insualtion bad or something). I still have to put the headlight in and taillight in and see if they work but I am not getting stray voltage running through out the entire motorcycle anymore!!! I am going to get a new spark plug becasue I do not even want that plug in the head even if it is not being used. I'll let you guys know the outcome in a few days. I cannot believe that was the problem A SPARK PLUG LOL. Must be rare for a spark plug to malfunction like that.

So everything looks like it will work now I'll let yuo guys know and thanks for trying to help me out.

P.S. Well at least I found that other problem with the pulsar coil and I rewound that so good things do come from bad things sometimes i guess.


O yea just so you guys know it is a DENSO spark plug W22FS-U
DM

[dsm6678]

Update on electrical problem kt 250 blowing lights.

Sorry guys, I made a little mistake! It turns out it was NOT the spark plug it was the spark plug wire. It's kinda touching the exhaust and I guess the insulation is old and letting it arc a little throught the plug wire to the exhaust..

I apoligize for my mistake if anybody is still reading this post. Plus I hope someone with this problem can use the information here to help them..

DM

Edited by dsm6678, 18 January 2012 - 02:44 AM.

[dsm6678]

I had to buy an aftermarket coil and make a bracket but it is working. I installed the 6 volt tailight and 6 volt 35 watt headlight and they are not blowing out anymore and no more voltage running through the bike frame so I seems the coil was leaking voltage or something. Hope no one else ever has a problem like this it seems unheard of!

dm

[BigMike1961]

Good to know you fixed it, my first Trials bike was a KT. Should never have sold it.