Topic: Charging troubleshooting

[Lumbee]

Hey guys. Doing some troubling shooting on my 'matic chopper. The motor is a 77 Hondamatic. Based on the troubleshooting guide in the garage section at Hondachopper, when I measure the resistance between the green and white wires (the field coil) I am getting a reading of 4.5. The troubleshooting guide says it should be 7.5. I know the hondamatic had a slightly different charging system (more powerful?) than the regular 750's so I wanted to check to see if this number might be correct before changing the field coil.

Thanks in Advance.

Heres a little eye candy https://photos.app.goo.gl/MUrxQ45TsHXemGzdA

[sammon287]

Did you ever find an answer to this question? I'm also trying to diagnose a charging problem with my 76 Hondamatic. I'm trying to test everything I can externally before doing anything requiring gaskets or Hondabond. Sorry I can't help you since I think you sound more knowledgable on the topic than I am.

[Lumbee]

Thanks for commiserating  No, no solution yet. I did try one of these and nothing:

https://smile.amazon.com/dp/B07WMQ2BFS?psc=1&ref=ppx_yo2_dt_b_product_details

Pulled the cover off this weekend just to check out the condition of the field coil and wires on the inside and everything passed the eyeball test.

Not sure what my next move is, but I will post back here when I make it.

[Lumbee]

OK I found this one; it specifically mentions the 750a as compatible so I have one on the way. I'll let you know how it works (fingers crossed)

https://www.dbelectrical.com/products/new-voltage-regulator-honda-cb350-cb400f-cb550-cb55f-cb550k-cb750-cb750a.html

[sammon287]

Can the stator and field coil wire connectors be reached under the starter motor without removing the generator cover? It's been over a year since I had it all apart and I can't remember. I really don't want to mess with the shifter cover since it uses a unique gasket and is currently leak free, but I don't think that has to come off for access. Did you test the stator at the rectifier connection? I need to check the bullet connectors near the starter. Everything worked before I disassembled and reassembled the engine over the course of 18 months or so. My rectifier passed the FSM tests. I did have an issue with a melted fuse box at the main 15A circuit. I replaced the fuse box and cleaned the connections to the regulator and rectifier which seems to have solved the overheated circuit issue, but maybe it fried something I can't see.

[Lumbee]

I was able to pull the generator cover off without removing the shifter cover. I was a bit tight getting it back together; the wires don't want to clear the edge of the shifter cover, but I was able to get it back together. I followed the troubleshooting guide here and all my stuff checked out:

http://www.hondachopper.com/garage/troubleshooting_charging_system/troubleshooting_charging_system.pdf

Worth going through to sanity check everything has the correct resistance. Here were the readings I got: https://photos.app.goo.gl/UZ9VcRkG55yZpH26A

[sammon287]

That's helpful. Thanks.

[sammon287]

  After following the hondachopper.com troubleshooting guide, which I found easier to comprehend then the FSM, it looks like my field coil is bad. It reads 4.3 ohms between the wires and has continuity to ground through both wires. I'm not sure how that happened with it out of the engine and in a ziploc bag for a long time. I guess I'm looking for a used one. (I tested the stator first, as indicated in the guide and the readings on all three legs were consistent, but very low).

[Alan F.]

LD120-01 should be stamped on a 750A field coil. A good one measures about 14.1 ohms.

You can find good deals on some 750A parts by searching ebay stores where there just isn't much traffic and parts sit around a long time.

[Lumbee]

Ok, just to follow up on this, I swapped out the entire left side cover with another that I had from a parts motor and it is now charging. I used the el cheapo regulator/rectifier and it seems to work fine https://www.ebay.com/itm/232527880611

[sammon287]

LD120-01 should be stamped on a 750A field coil. A good one measures about 14.1 ohms.

You can find good deals on some 750A parts by searching ebay stores where there just isn't much traffic and parts sit around a long time.

Did you mean 4.1 ohms? I received a used field coil (marked LD120-01) yesterday and it measures about 4 ohms, the same as my original one. The replacement has no continuity from wires to case, in contrast to the installed one that appears to be shorted to ground. The regulator and rectifier pass the book tests, so I hope this fixes it. I'm still waiting for a cover gasket before I take it apart.

[sammon287]

  I'm still struggling with this. Once I removed the alternator cover and tested the field coil while disconnected from the harness, it checks out exactly the same as the Ebay replacement (4.0 ohms between wires and no continuity between white or green wires to the field coil case. When I thought the field coil was shorted internally, I was testing at the wire connections to the regulator, so it was grounded through the wiring harness when it was connected. The wires in the harness that the field coil plugs into and go to the regulator seem to be OK (namely the white wire is not shorted to ground).
  I'm not sure what to try next. I don't see how replacing the field coil with an identical one will change anything. I found it impossible to access the charging wire connectors without removing the shifter assembly and I hate to keep ordering more gaskets.

[Lumbee]

I'll say mine look fine also...no frayed wires, or anything look deteriorated. I think I have heard of other 750a's having charging issues whereas I almost never hear of any of the other models (K or F) having issues. So it could be something that's not obvious about the automatic that is at fault.

Regardless, if you are out of options I would find a used K or F model stator and give it a try. You can lose anything (except money) at this point, and if it does not work, then you [somewhat] confidence say that it's not the stator that is the issue.

This one is price reasonable https://www.ebay.com/itm/254941232177.

Good luck...i know it sucks...but when you see that 13.5v on you multimeter it'll all be worth it! 

[Alan F.]

LD120-01 should be stamped on a 750A field coil. A good one measures about 14.1 ohms.

You can find good deals on some 750A parts by searching ebay stores where there just isn't much traffic and parts sit around a long time.

Did you mean 4.1 ohms? I received a used field coil (marked LD120-01) yesterday and it measures about 4 ohms, the same as my original one. The replacement has no continuity from wires to case, in contrast to the installed one that appears to be shorted to ground. The regulator and rectifier pass the book tests, so I hope this fixes it. I'm still waiting for a cover gasket before I take it apart.

Sorry to get back so late, 14.1 is what I measured.