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CT70K3....Is my flywheel bad?

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yadihonda

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Discussion starter · #1 ·
I have an CT70K3 original points motor. Headlights work fine but battery keeps draining and I lose the blinkers/tail lights. When I read the DC at the battery, I'm only reading about 2 volts. When I read the AC before the rectifier, I'm only reading about 2 volts. It is a brand new stator rebuild kit (coils, condenser, points). From a visual perspective, the spark looks weak (I replaced the coil and wiring harness as well on the bike).

Would a rotor/flywheel lose magnetism and effectiveness? Does anyone know the symptoms? I believe I could feel the magnetic field when I was working with it, so nothing obvious struck me at that time.
 
#2 ·
If a screwdriver sticks to the fly wheel and takes some effort to remove, the flywheel is fine. If you replaced the whole stator assembly did you get the right one? Honda used stator assemblies/flywheels from Hitachi and Mitsubishi. You can't use a Mit stator with a Hit flywheel and vice versa.
 
Discussion starter · #5 ·
My reply disappeared so excuse me if this is a repeat: I gapped the points at their widest opening. I replaced the stator coils, condensor, points, ignition coil, and wiring harness on the bike. I would think that a good spark would be the least of my worries. That, combined with the lack of voltage at the battery, is making me think about the magnet not being effective.......or maybe like you said, the coils are not correct.
 
#6 ·
My first thought is that you swapped the ignition and lighting coil which is why I asked about the spark. I know both coils have different resistance values, but I don't know what they are.

Try setting your timing so the points begin to open when the "F" mark on the flywheel aligns with the pointer. You can use an ohm meter or a battery powered test light.

The main difference between Hit and Mit ignitions is the distance between the coil and the inside of the flywheel. This gap is critical for producing the correct voltage.
 
Discussion starter · #7 ·
I actually kept the old coils intact for comparison if needed. But if I recall correctly, the coils came out of the package already wired up, but I'm relying on bad memory. I'll give the points adjustment another shot using an ohm meter. Thanks for the advice.
 
Discussion starter · #9 ·
VintageMX.... I just had a thought. If my headlights are bright and working when the engine is running, then wouldn't that be indicating a good lighting/charging coil? Maybe something else is causing the low reading of AC before the rectifier? For some reason I just thought that battery was between the stator and the rest of the electrics, but given the bike runs, with headlight, when the battery is removed, that can't be true. I need to take another look at the schematic.
 
#10 ·
Does the light get brighter when you rev the engine?

Check voltage going to the headlight.

Been a while since I messed with a bike that had a battery. The lighting coil produces unregulated A/C voltage which then needs to be regulated and rectified into DC voltage.

Does your bike use a separate regulator and rectifier?

Are they for the correct voltage (I assume you have a 6v system)?

Are you checking voltage coming out of the alternator before the regulator or regulator/rectifier?

One thing to always check with electrical circuits is the ground. It's always the ground!
 
Discussion starter · #11 ·
Update: the flywheel checked out. It definitely has a strong magnet. I reset the points and it appears to have a better spark but couldn't actually test on the account of my woodruff key partially shearing. Either it was that way and I never noticed until now, or I just did it now. Either way, the bike fired right up but then I noticed the flywheel wasn't fully seated so I killed it. Now I wait for the mailman.

Regarding the battery and charging issues: The light gets brighter with revs. I will check the voltage to the headlight - it's just a nightmare pulling the light apart with all the wires cramped in there. It's a birds nest of connections for the blinkers, lights and switches. The bike uses a separate rectifier and the battery acts as the regulator. I thought I was checking the AC before the rectifier and battery, but now I'm thinking it isn't a straight shot up to the battery; there is the ignition and possibly headlights in between. I have to find some time to sort this mess out. Also, I can't easily check the AC directly from the alternator because the connector is hidden inside the frame behind the air cleaner. That will be the last thing I check once I'm convinced I have it all wired up good otherwise.

Regarding the ground...you are so right. I've learned the hard way in the past to make sure the grounds are all solid.
 
#12 ·
Good to hear! Those 3mm woodruff keys are notorious for shearing, especially if the timing is too far advanced or the motor has been built. Do yourself a favor and buy a spare or two.

Sounds like the headlight is getting voltage right from the lighting coil. Seems odd. I'm not familiar with the electrical circuit on that particular model, but I have made a few dirt bikes into dual sports. I always used a combo regulator/rectifier which was wired into the lighting coil before the battery. This limited DC volts to ~13.5 before the battery. If you measured unregulated AC voltage out of the alternator it would just keep increasing as RPMs rise. If left unregulated it will blow bulbs.
 
Discussion starter · #13 ·
You are correct....the ac will keep rising with revs and if the battery isn't in there, it theoretically could blow the bulbs, but I don't think it gets that bright on this bike, so maybe my volts are somewhat short at the light. I guess I will start by measuring the volts at the headlight. If they are good there (<6 DCV) then it has to be a wiring issue.
 
Discussion starter · #15 ·
I tested the rectifier with an ohm meter....just guessing at the procedure as I really don't know for sure how to test it. Measuring resistance, it gave a reading in one direction only (+/-) which is how I believe it is supposed to work. Now, if that rectifier has gone bad is creating some sort of resistance, I wouldn't know, but I'm guessing it would get hot or something.

Your Bultaco story does remind me that I have a z50 with a charging coil (the motor was from an s65) and it blows lights. I could never figure it out but because I had people telling me that it shouldn't blow the lights. At idle it would be dim. At full throttle...look out, the lights would get crazy bright then poof....kind of funny to see. I found some different wattage bulbs that I was going to try to see if that would bleed off some of the current. I thought about 12v bulbs if I could find any to fit the stock sockets.
 
#16 · (Edited)
yadihonda said:
I have an CT70K3 original points motor. Headlights work fine but battery keeps draining and I lose the blinkers/tail lights. When I read the DC at the battery, I'm only reading about 2 volts. When I read the AC before the rectifier, I'm only reading about 2 volts. It is a brand new stator rebuild kit (coils, condenser, points). From a visual perspective, the spark looks weak (I replaced the coil and wiring harness as well on the bike).

Would a rotor/flywheel lose magnetism and effectiveness? Does anyone know the symptoms? I believe I could feel the magnetic field when I was working with it, so nothing obvious struck me at that time.
Click to expand...
Just curious if your stator rebuild involved changing out the plate. The difference between some of these bikes is the height of the mounts on the stator plates. The manual vs. automatic models on this era bike were that way. If you have your old parts, do a comparison. Another question would be is whether your headlights come on without the engine on. If so, you may be using the wrong circuit, drawing off the battery. The Taillight and horn should work with the engine on, key in the accessory position, but the headlight comes directly off the coil and only when the engine is running. Honda figured you still need brake lights if your motor goes dead, but not headlights, a safety feature.
 
#18 ·
yadihonda said:
I have a z50 with a charging coil (the motor was from an s65) and it blows lights. I could never figure it out but because I had people telling me that it shouldn't blow the lights. At idle it would be dim. At full throttle...look out, the lights would get crazy bright then poof....kind of funny to see. I found some different wattage bulbs that I was going to try to see if that would bleed off some of the current. I thought about 12v bulbs if I could find any to fit the stock sockets.
Click to expand...
A resistor wired in parallel to the circuit would work. Done that before too.
 
Discussion starter · #19 ·
davmo said:
Just curious if your stator rebuild involved changing out the plate. The difference between some of these bikes is the height of the mounts on the stator plates. The manual vs. automatic models on this era bike were that way. If you have your old parts, do a comparison. Another question would be is whether your headlights come on without the engine on. If so, you may be using the wrong circuit, drawing off the battery. The Taillight and horn should work with the engine on, key in the accessory position, but the headlight comes directly off the coil and only when the engine is running. Honda figured you still need brake lights if your motor goes dead, but not headlights, a safety feature.
Click to expand...
I used the original stator plate and just added new coils, condenser and points (and seals). With the battery out (or dead), the headlight comes on with the engine . The tail lights do not come on with the engine. They do come on with a fresh battery in. Are you saying that the tail lights should come on with the engine as well? Or do they run strictly off the battery?

The horn is actually disconnected because it was bad and shorted.....and popped the fuse whenever the horn button was touched.
 
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vintagemx
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