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Stator Removal for CM400A [SOLVED]

Maraakate

Maraakate

Veteran Member
Joined
Jun 7, 2022
Total Posts
2,579
Total likes
693
Location
Lancaster, PA, USA
Hey all,

I was working on making a guide for testing the Hondamatic ignition system and went to test the pink and green wires and got no resistance. I made sure it wasn't dirty leads or anything funny like that. After that was verified, I started the bike with a timing light and found out this is for the advance and sure enough it does not advance to the | | marks when giving it some good throttle. It DOES move from N to F like it's supposed to. I tried my homebrew CDI and the original just to make certain. Apparently I've been driving it like this for a long time and never noticed.

With that said I suppose this means I need a special tool to remove the rotor right? If yes, where can I get it? And who can you recommend to send it off to get it rewired? The rest of the stator ohm'ed out within spec.

Kind of funny I've driving it like this for years and never really noticed anything.
 
Wow, that's all it is huh? I guess I need that holder tool too. I see you can get some cheap ones on ebay that do 7mm and 9mm holes: https://www.ebay.com/itm/264460086551. I have to measure what it is on the stator itself. I'm assuming the holder tool I linked to will work just fine.

I was looking at using this person for the stator repair: https://www.rickystator.com/page/rewinds. Has anyone used this person before? If Custom Rewind has particular experience with this bike though that might be worth doing. Shipping to the UK will probably be ridiculous, unless it's really the only person left we can trust to do it properly.
 
Hmm, I just checked and the hole sizes on the stator are 18mm. Looks like I'll need to find a larger flywheel holder tool for that.
 
I went ahead and ordered the puller and a holder I think should work. I may get lucky and it's just stray wire on the top of that coil that can be very careful soldered back on. I've seen some arcade guys fix HV coil leads by peeling back the magnet wire slightly soldering it back together then using clear nail polish or something similar to insulate and check the resistance. If it's internal though, it will definitely have to be sent out.
 
Yeah, ill see. Otherwise ill use custom rewind. I did order a 12mm piston stop as well. Might be easier than the holding tool. Guess we'll find out soon.
 
I and several other members have bought rewound stators from Custom Rewind without any complaints. I sold my A model a couple years ago to a friend and after about 7 years the stator is still working. The bike has not been ridden a lot and is stored inside. So that might make a difference.

Bill H
 
old timer said:
I and several other members have bought rewound stators from Custom Rewind without any complaints. I sold my A model a couple years ago to a friend and after about 7 years the stator is still working. The bike has not been ridden a lot and is stored inside. So that might make a difference.

Bill H
Click to expand...

Yes unfortunately mine was stored outside, with a cover, for years as I had no other way to keep it around. So that may have been part of the issue.

We'll find out soon enough when I get the tools to pop it off. Praying its just the end and needs tack soldered back on.
 
The rewound stator may put out a little bit more voltage then the the original . I could of had a bad one when I changed the stator but even with the new one I had 14.7 volts to the battery. I think 14.6 is max but could be wrong. Memory not what it use to be. LDR may jump in here.

Bill H
 
I see what you mean. I will wait and see. Those diodes in those rarely go bad in my experience unless there was a bad ground that was intermittent and kept triggering it off/on very rapidly.
 
Hey Jim,

I saw you mentioned that in another thread somewhere and was taking a look. I'd be interested in a modern replacement, but what's the cost and does it mount up? I'm not equipped to fab up brackets in my shop.
 
It's a bit larger
201_4701.jpg
This is the original mounting where the regulator is behind the bracket on the right side
201_4565.jpg
I moved it to the front and tucked all the other connectors behind the bracket
201_4749.jpg
 
Considering the stator rewind (if needed) is going to cost probably $200-$300 the regulator upgrade will probably have to wait until the end of the season.
 
As I wait for tools, I called Ricky Stator and they said they don't deal with street bikes. However, he referred me to Rick's Motor Sport Electrics out in NH. I called them, they do have it listed in their database as having worked on them before. Typical cost to do a complete rewind is about $285. They informed if it is just indeed that one coil and they don't have to remove the rest to get to it then the cost would be lower. So about $200-$300 is what I was anticipating.

For those curious, that site is https://ricksmotorsportelectrics.com/partrebuild.php. You click on the Part Rebuild Form and fill out the information and ship it to them.

I'll give the fellow in AL a call as well to check their pricing.
 
Maraakate said:
Yeah, ill see. Otherwise ill use custom rewind. I did order a 12mm piston stop as well. Might be easier than the holding tool. Guess we'll find out soon.
Click to expand...
A piston stop is NOT a crankshaft holding tool, screwing it in there to hold the crank while you wrench on the puller or the nut will certainly damage the piston.
 
16555053308704784437880060261930.jpg

I'm having a hard time getting the stator off. I got the bolt out which required a long breaker bar. The removal tool i turn clockwise until it stops then tried going some more with a breaker bar but I'm afraid of cracking it. Am I doing something wrong?
 
After tightening the "removal" bolt/puller, tap moderately on the end of the bolt with a hammer and then try tightening it again, then repeat. It takes a bit to get it loose from the taper it's probably been on for over 40 years.
 
Ok, I'm still at it this time with an impact hammer still can't get it. Nothing is rusted its actually very clean in there. Am I going to need to carefully put penetrating oil in there?

16555071258982664749382086822718.jpg
 
You have to be careful or you can affect the magnetism negatively by hammering on it too hard, that's why I mentioned moderately. A little penetrant can't hurt. Jim probably knows a trick, he's the guy on these engines.
 
Ok. I put the main bolt back in it still runs. I'm used to the pullers that have an additional bolt going through them and you tighten them at the same time. You would think they make one like that for this but I guess they dont.
 
Since the end of the crankshaft has a threaded hole, I'm sure it's because they didn't want the center bolt in a puller to damage the end of the threaded hole making the bolt that holds the rotor impossible to reinstall. Most Honda alternator rotors use the same method. The lost magnetism won't usually affect it running, but it can reduce the alternator output some.
 
It was inevitable, they rarely put up that much of a fight and you did all the hard work minutes before. I'm sure the penetrant helped it the rest of the way, or it was just ready to pop.
 
Well it looks like its possible for someone to rewind only the advance coil as its the coil held in with two screws. There was a slight bit exposed near the epoxy for the pink wire and continuity from the 6 pin to that read good. I'm wondering if that epoxy failure eventually shorted it to ground and killed it. But good to know it should be repairable without having to rewind the entire unit.

And yeah that thing was almost as fun as getting the oil pump off the cb550k. Took an hour of back and forth to get that thing to come off to replace the o rings.
 
Cleaned that exposed part with some acetone then used clear nail polish to temporarily seal it off. Put everything back together and used blue lock tight on the JIS screws. Started it up and verified the charging circuit. Still good. So ill need to send these pics off to Rick to see if they can just rewind that small coil for me.
 
Emailed Rick's with the pictures. We'll see if they'll take it on to just do that coil by itself. I don't see any reason why they can't/won't.
 
So, the crack in the epoxy is allowing voltage from your advance circuit to escape and disable the timing advance ? This being akin to a cracked white porcelain/ceramic spark plug insulator that allows the HT voltage to "jump" out of the spark plug before it gets to the plug's electrode/engine's combustion chamber and causes an engine's misfire ?
 
Boosted said:
So, the crack in the epoxy is allowing voltage from your advance circuit to escape and disable the timing advance ? This being akin to a cracked white porcelain/ceramic spark plug insulator that allows the HT voltage to "jump" out of the spark plug before it gets to the plug's electrode/engine's combustion chamber and causes an engine's misfire ?
Click to expand...
No, there's a problem with the windings that needs to be addressed. It's quite possible that the cracked epoxy allowed moisture to enter and corrode some of the windings.
 
It did look corroded where the pink wire enters the winding and epoxy was chipped off there. My guess is thats where it started or either that large crack underneath from all the heat/cool cycles over 40 years.
 
Rick's stator can just do the individual coil. So I'll send that out this week and get that done and report back on how it went.
 
Rick's quoted about $150 and 2-4 weeks turn around to get it done. A bit higher than I was expecting for such a tiny coil, but you gotta do what you gotta do with these old bikes sometimes. :lol:
 
For kicks i gave custom rewind a call as well to see their price.

Got the advance coil off, which was "fun" because the pvc sleeving was no longer flexible. Had to carefully cut and remove that, remove the grommets, disconnect the pin connectors with the proper tool and get it out. I used this opportunity to freshen it up with new sleeving and harness tape and clean the connectors. Put it all back together, still running and charging.

20220623_160424.jpg
 
Yes he just called me back and its 40 dollars shipped and he has spares ready to go so its more of a core exchange. Who to go with is a no Brainer!
 
Thanks Maraakate for this thread and all the great pictures. That whole stator assembly is an odd looking beast. And that secondary advanced coil that went bad is as well, the way it bolts on and somehow operates on the inside shaft. You've got some pictures of the primary coil pickup that mount outside the rotor. It's about twice as small as the one on my 81 CM400T, maybe mine is a newer model or it's just different with automatic. Like you have the change relay on the CM400A, whereas I don't have that, the starter solenoid current all goes thru my little ol starter button. Which I have had to take apart a number of times due to the contacts getting oxidized and needing cleaning.

Taking that off looked like more work than you would expect. I can see how you need to hold down the main crack shaft with those two holes on either side, and then I assume you just remove the big bolt in the center. I assume the hub assembly is notched, or keyed onto that, and pressed on as a tight fit. So does the special tool screw into a set of threads specially for pulling it off the crank shaft? Does the main bolt pull it back on? I suppose I should go read the FSM ;) Anyhow, good luck with it. I like how you put it back together to see if it still works. I found myself doing that with the carbs - geez, hope I can get this thing all back together and haven't lost any pieces. Now one interesting thing is that it tells me something about the importance of the advancing of the ignition with RPM(as being maybe not all that important or critical). It sound like something that can help if you want to maximize your power, but I tend to agree that these are not racing bikes. I'm just happy if it runs reasonably well. It should be interesting what you find out with yours, like if you notice much of a difference.
 
kbongos said:
Thanks Maraakate for this thread and all the great pictures. That whole stator assembly is an odd looking beast. And that secondary advanced coil that went bad is as well, the way it bolts on and somehow operates on the inside shaft. You've got some pictures of the primary coil pickup that mount outside the rotor. It's about twice as small as the one on my 81 CM400T, maybe mine is a newer model or it's just different with automatic. Like you have the change relay on the CM400A, whereas I don't have that, the starter solenoid current all goes thru my little ol starter button. Which I have had to take apart a number of times due to the contacts getting oxidized and needing cleaning.

Taking that off looked like more work than you would expect. I can see how you need to hold down the main crack shaft with those two holes on either side, and then I assume you just remove the big bolt in the center. I assume the hub assembly is notched, or keyed onto that, and pressed on as a tight fit. So does the special tool screw into a set of threads specially for pulling it off the crank shaft? Does the main bolt pull it back on? I suppose I should go read the FSM ;) Anyhow, good luck with it. I like how you put it back together to see if it still works. I found myself doing that with the carbs - geez, hope I can get this thing all back together and haven't lost any pieces. Now one interesting thing is that it tells me something about the importance of the advancing of the ignition with RPM(as being maybe not all that important or critical). It sound like something that can help if you want to maximize your power, but I tend to agree that these are not racing bikes. I'm just happy if it runs reasonably well. It should be interesting what you find out with yours, like if you notice much of a difference.
Click to expand...

I get a feeling it's been like this since I've owned it and never noticed. The bike does reach its advertised speed (though have to be tucked bombing a hill for that <G>). It will be interesting to see how much of a difference it makes. I'm guessing it probably pulls a bit quicker at mid throttle.

Yes, you basically use the holder tool and remove the bolt. Then use the rotor tool thread it in and with the holder tool still attached try to give it another turn when the rotor removal bolt gets tight and it should pop off. It didn't right away for me, as you've seen here. I had to end up spraying some PB Blaster and letting it sit for 5 minutes then it came right off. There's a woodruff key in there as well. Mine was still in place I didn't bother to disturb it. But yes, you slip it back on as tight as you can by hand then use the bolt to get it back on the rest of the way.

I'm guessing, but have no idea, that the advance coil probably plays a bigger role in the CM400T series bikes. But, if your 400T runs, just simply disconnect the advance coil on the 6 pin connector (pink wire only, need the green which is ground for the CDI), go for a ride and see if there's any real difference. You can carefully remove that connector with a non-angled pick tool or Vintage Connections/Sparck Moto sells the proper tool that makes it a lot easier.

And yes, any kind of decent change like this I always have to check. It's too easy to just do one thing, let it sit then get bored do other stuff to it and then nothing works and you chase your tail trying to narrow it down which thing to undo/what did you break. I'm still actively riding the bike.
 
A note about the woodruff key in the crankshaft. If the rotor is not torqued down to spec the rotor can/will bounce against it shearing it off in most cases. In other cases it destroys the crankshaft. Always check that the key is tight, it's an interference fit so if you can't move it by hand you're good.
Here's the result of a loose rotor
GEDC2482.jpg
 
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