Rewinding a bad stator, because why do things the easy way

[tr1ppler]

So I have a penchant to go down roads to "Save money" that end up costing me more money but I also like doing things the hard way.  So this is a realization of those two tendancies 

A big part of me working on this bike is to learn as much as I can.  This is the first bike I've actually dug into the motor at all past the valve cover, I've painted a bunch of bits, I'm trying to learn whatever I can, and part of that is the next step.  Rewinding the stator.

The good news.  The field coil tested okay.  Didn't ground to the core and had 4.9 ohms of resistance from lead to lead.  

So I tested the 3 legs of the stator and instead of 0.7 ohms on each leg of the triangle, as expected, I got 24, 27, and 6 ohms.  So not close.  

Also based on the burned out stator connector and the signs of an exploded battery all over the exhaust I think this is the reason the bike was parked in the first place.  That history is 3 owners past so I'm trying to piece it together forensically.

Could I buy one on eBay?  Yes.  2 reasons why I am not doing this. 
1) I am not entirely sure that the "new" stator would be a lot better
2) I'm in this to learn what I can

So before jumping off the cliff, I thought I should do some due diligence.



So I opened it up and tore off all of the old white silicone that was used to seal off the wire passages by one of the POs.

I took out the field coil because I could not see that there are 2 bullet connectors that allow you to leave it in the side cover when you remove the stator and wiring.  They were covered in the white silicone.



I thought I would try and test the 3 wires at the stator end to see if the bad resistance was coming from the harness itself.  The fabric wire sleeves were pure carbon and broke up if touched, taking the wires with them.  So now I was officially huptey-juped, I was very successful at ensuring I had to rebuild this whole thing by accidentally breaking it.

The good news (sort of) is that testing the leads to the union of the 3 wires confirmed that the wires in the stator themselves are bad.  I got these three results:

5.3 ohms
22 ohms
0.7 ohms



So one of the 3 legs is good.  One is bad. One is terrible. So at least I don't have to rebuild it because I broke the wires but because the wraps are bad.  This stator is Delta wound which means the 3 legs junction at one place.

So after the initial inspection, I found that the wire looks to be 19 gauge.  I'm thinking of rewrapping with 18 gauge and seeing if I can put in a few extra turns to increase the output.  I'm no electrical engineer and haven't found anything that I totally understand yet, so those decisions are still forthcoming.

Next step is to unwind the current stator to look at the wrap pattern and see how much magnet wire I will need.

[tr1ppler]

So I started on dissection.  I've had trouble getting information on EM stators since the permanent magnet variety are so much more common but I'm happy with what I see here.

The biggest pain was trying to remove the lacquered in fiberboard pieces that prevent the coils from spilling out, without damaging the coils behind them.  Once I did this I was able to count 17 wraps for each pole.  

I reached out to Matthew from SparkMoto and he said that their EM R/R unit will work with this unit if my current Reg & Rec give me any trouble after the re-wrap.  They test to spec as well as I can test without a battery and working alternator but I'm happy to have the fallback.  He suggested 16 gauge magnet wire.  Best I can tell it had 19 previously but there does look to be room for a little extra wire in there.


Fully Hooped.  Hopefully, I can get it back together


I was expecting the wraps to change direction each time as they do on the Perm Magnet stators but they seem to wrap in the same direction every time.

The wraps measure 1.5 CM above and below the core on my unit.  The first wrap I counted 17 full wraps.  I'm going to do a few more to make sure I counted correctly before pulling the whole unit apart.

It actually looks a lot simpler and faster to re-wrap than other units I've seen.  Cautiously optimistic.

[tr1ppler]

So finally made some progress.  

First I used a quick punch to mark every 5th pole so that I had a reference for my diagram.  Due to the drilling of the bolt holes and the pass-through hole for the secondary coil wires things need to be in a specific place.

I carefully took out another 2 wraps and found that I'm looking at 18 wraps per pole as opposed to the 17 I thought I had initially.  I may see if I can fit 19 since I plan on upgrading the Reg/rec to a modern unit.

So I started to take it apart but cutting out the fiber pieces that held in the wraps was a real bear.  I first used a utility blade that took forever, then I pulled out the hacksaw and cut down through each one.  Then I cut the loops on the outside with the old bandsaw.





Once I had the wires out I used a brass brush spinning in my lathe to take the lacquer off.  I tried burning it off but that didn't seem to work as well as I wanted and the brass brush made quick work of everything, making it nice and shiny.  Cleaning between the arms was a little less fun.  I used a diamond bit in my "dremel" to clean out as much as I could.  I ran out of time but I'm going to finish cleaning them up with small files and round out the edges before the re-wrap.




Looking at what to use to insulate the core from the wraps as well as hold everything in place.  I'm looking at Glyptol for the stator body (kind of pricey though at $50 a small can) and then I've read about several 3M epoxies that are designed for the oil and heat cycles (but also pricey).  I've heard of people using Normal HT epoxy but I'd really rather it be a long-term fix done right, but with the cost of those 2 products I'm getting close to the "Should of just sent it to be re-wrapped" price range.  

[scrambler]

Cool! I love these kind of projects that obviously make no sense at all bc you could just buy a working stator for cheap in a fraction of time you spend on it but the joy of rebuilding something yourself keeps your dopamine level so high that you don`t care Great stuff, I`m curious to see the result. Keep us posted! 

[tr1ppler]

I'm glad someone gets it

[tr1ppler]

So I still am hoping to do this but I did see some pretty cheap stators on Ebay and ordered one. Should be here next Friday. Interested to see if it tests okay. I'd like a point to measure against to see if re-winding provides any benefits.