New Reg/Rec, Stator, and Rotor... Now What!!!

voodoo

voodoo

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Okay... I'm about to pull my freakin' hair out over here! I just replaced the stator, rotor, brushes, and reg/rec on my 1981 XS650 SH.

I also have just COMPLETELY rebuilt the carbs with performance needles and jets from Mike's XS (where I get all my parts!)

Here's the deal...

When I give some throttle, she sputters and backfires like crap!!! Voltage reading on the battery is just hovering around 14v at very high throttle.

When I unplug the Reg/Rec, the motor SCREAMS like a bat-outa-hell!

All my windings have tested good however, my brushes are still showing 6 ohms across each other. Rotor at .5 ohms across rings... so I know it is good!

If there was a short on one of the brush leads, wouldn't it have trouble putting out 14v? What is causing this sputtering and backfiring??? I know it's electrically related somehow!

Has anyone run across this and lived to tell about it???

:banghead:
 
by the way, I thought I would add...

I ran across a similar post:

http://www.xs650.com/forum/showthread.php?t=3487&highlight=sputters+backfires

And I too noticed that when I removed my green wire (outside brush) from the stator, it would run like it should. When I would touch the green wire back to the brush, it would throw a spark inside the stator housing and start running like crap again!

Keep in mind... the stator rotor AND regulator/rectifier are brand spanking new!
 
Or... It could be that I don't know how to use my damn multimeter!

I'm going to double check it tonight. The part was ordered from Electro Sports, not Mike's XS, so I'm hoping they will honor an exchange if it was DOA!

Illnlit you all know...
 
It sounds like a weak magnet in the rotor. The 81 has the TCI ignition. On the stator is a pickup, this pickup senses the magnet in the rotor. If the magnet is weak the magnetic feild of the rotor can be stronger than the magnet. This disrupts the magnets effect on the pickups.
Some one with this problem epoxied a new magnet over the magnet in the rotor. This stronger magnet made the bike run fine.
The thread on fixing the magnet is on here some where. Or was it at the Garage?
 
I believe it was in the garage. I'll go search over there and see what I can dig up...

By the way... I spent some time with my ohm meter tonight and this is what I came up with-

the pos and neg wires at the plastic terminal tested out at 8.7 ohms.
The pos and neg connections at the brushes tested out at 8.6 ohms.
The three white wires from the stator tested out at 0.6 ohms across each other.
The brushes themselves (brand new) tested at 1.5 ohm.
When the brushes were installed, they tested at 8.8 across each other.
The rotor itself (brand new from electro sports) tested at 5.0 across the rings.

I really hope it turns out to be something simple like a stronger magnet. Is it possible that when I put power to the brushes that it is disrupting the mAgnetic field enough to disturb the pickup coil function?
 
Plattey did it. Thread "just a weak battery". I was just reading it.
Thats what Plattey and Pamcopete figured out. The magnetic feild of the rotor is strong enough to disrupt the may the magnet effects the pickup.
 
I remember a member here recently cured a problem like the one in the thread at the garage by replacing the four egg-shaped diodes in the tci box. Interestingly, those diodes go directly to the pickup!

Addressing those diodes might be attacking the problem from the other side and a more reasonable fix possibly Those diodes are fragile and I know of at least one that turned into resistor. In the tci each wire to the coil has two diodes in series, probably to give two diode drops (voltage drops) relative to some reference.

Would be interesting to put a cheap gauss meter on the magnet and see if it's really weak or if it in reality just needs to be stronger to overcome the effect of bad diodes.
 
Been researching the entire "weak magnet" problem in forums across the net and from what I've read, the diodes (or transistors rather) are the most likely fix. I popped the case open and sure enough... the diode test I ran on the transistor showed a bad leg. I stopped by Radio Shack this morning and threw down an entire $1.60 for a new TPI-120 transistor. If I end up fixing this dilemma for $1.60, I don't know if I'm going to jump for joy or commit suicide!!! :)

IMG_7174b.jpg
 
To test a transistor in an unknown circuit you need to unsolder it. Before you replace it, while it's unsoldered, test it again. If it tests good, solder it back. Test the four yellow and white diodes on the upper right of the pic. There's invisible conformal coating you need to scrape off their pads to get to the solder. You can test them without unsoldering them because their ends are open when the box is unplugged.

Having just gone over a box real thoroughly, I suspect the big transistor is least likely to be the problem, if there's any problem with the box. Look on the solder side for solder joints that have a ring around the protruding lead or that look like a little cylinder of solder is attached to the lead and pushed up. Carefully re-solder those. They look like they're making contact well enough, but they demonstrably aren't.
 
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xjwmx said:
To test a transistor in an unknown circuit you need to unsolder it. Before you replace it, while it's unsoldered, test it again. If it tests good, solder it back. Test the four yellow and white diodes on the upper right of the pic. There's invisible conformal coating you need to scrape off their pads to get to the solder. You can test them without unsoldering them because their ends are open when the box is unplugged.

Having just gone over a box real thoroughly, I suspect the big transistor is least likely to be the problem, if there's any problem with the box. Look on the solder side for solder joints that have a ring around the protruding lead or that look like a little cylinder of solder is attached to the lead and pushed up. Carefully re-solder those. They look like they're making contact well enough, but they demonstrably aren't.
Click to expand...

I'll DEFINITELY check that out! And yes... The solder beneath the transistor has thin dark rings around them. If I remember correctly... The solder beneath the diodes have the rings as well! I will test the transistor when I pull it and let you know...
 
stupid solder rings... I have a 92 accord that has the main relay that fires the first injector, is widely known for crapping out in these particular cars. the relay is up under the dash, sandwiched between the criuse box, and underside of dash, adn starts runs fine , then when the cabin heats up, the car just dies.
A new relay is 60+ bucks, but I just resoldered the joints and it has lasted 2 yrs so far, 70k miles.
if you see a lighter color ring around the solder joint, that joint is weak. when it heats up, it loses connection. if you are unsure about soldering, take it to someone who knows solder. Im not a certified electrical soldere(there is such a thing) but I do know OF it, and you need to remove the old solder with a sucker, or a wick, and have a very good iron. (I use a Weller) use flux, and flux cored, and do a little reseach on soldering before you attemp, because there is a certain profile that is stronger than just a huge blob of shit .
 
Yep... Got a Weller and I'm using 60/40 .032 rosin-core solder. I have my FCC license and I've sweat a few connections in the past.

I do however have a question that I can't seem to find an answer for...

I checked the egg-shaped diodes (four of them) for continuity and they all checked out! But... what ohm should these things be resisting? Could they be bad?

I just found a video on YouTube of a guy claiming to have replaced (not resoldered) his four diodes in the CDI and his bike runs like a bat-outa-hell now...

 
If the diode reads high resistance one way and much lower the other way, that's about all you can test with a multimeter. It will tell you if it's open or shorted. On my tci two of the diodes measured the same both ways so I replaced all four. That's not me in the video, btw. I wish it was - he looks like he's having fun.

It's useful to have an extra tci box to test against when you're trying to track something down. I got one for $30 on ebay. Most guys on there are trying to sell them outright for $100 but occasionally someone auctions one.
 
xjwmx said:
If the diode reads high resistance one way and much lower the other way, that's about all you can test with a multimeter. It will tell you if it's open or shorted. On my tci two of the diodes measured the same both ways so I replaced all four. That's not me in the video, btw. I wish it was - he looks like he's having fun.

It's useful to have an extra tci box to test against when you're trying to track something down. I got one for $30 on ebay. Most guys on there are trying to sell them outright for $100 but occasionally someone auctions one.
Click to expand...

Mind if I ask... Do you have a part# for the diodes you used? I'm having a hell of a time trying to find those little egg-shaped bastards with the yellow band!
 
I used 1N4005 from Radio Shack. Someone else used 1N4004. Others would work.

Reading your original post, I'm not sure how likely the tci is to be the problem. I only brought up the tci because Leo brought up a problem that someone fixed with a stronger pickup magnet and I knew that someone else fixed similar symptoms by replacing the diodes in the pickup circuit. Your problem sounds more like something in the charging circuit to me.
 
xjwmx said:
I used 1N4005 from Radio Shack. Someone else used 1N4004. Others would work.

Reading your original post, I'm not sure how likely the tci is to be the problem. I only brought up the tci because Leo brought up a problem that someone fixed with a stronger pickup magnet and I knew that someone else fixed similar symptoms by replacing the diodes in the pickup circuit. Your problem sounds more like something in the charging circuit to me.
Click to expand...

Thanks for the info on the diodes!

All the equipment on the charging system has checked out. Besides the pickup coil itself, everything else is a week old fresh out of the box. EVERYTHING!!! plugs... boots... wires... coil... reg/rec... rotor... stator... brushes... brush holder... everything! The system has no problem cranking 14v across the board. The problem is that it sounds like the timing is off by two degrees and it spits-backfires-and-pops like a freakin' automatic shotgun!!! Unplug the power to the brushes, and it runs like a turbo-charged drag bike!!! (like anyone would be proud of!).

Although the pickup coil and CDI are separated from the charging system, they ARE affected by the magnetic field created when power is applied to the rotor. I'm thinking that the BRAND NEW rotor (from Electro Sports) is overpowering the pickup coil.

A stronger magnet would probably work, but I don't want to go drilling into a brand new $$$ rotor!!! Someone earlier put me on the path of the CDI and the transistor and diode replacement. The more info I dig up on the CDI rebuild, the more I'm convinced this is exactly what is happening! Problem is... even when I replace the diodes and transistor, i'm not sure how good of shape the rest of the board is in!

Before I go spending $100 (or more) on another 30 year old CDI, I would rather convert it over to Pamco Pete's wonderful ignition system. The thought of being able to adjust the advance appeals to me also!
 
You can adjust the timing by slotting the top hole on the pickup per an xsjohn mod. I did that so I can run 87 gas without knocking. Some are already slotted, and all you have to do is Dremel a screwdriver slot in the screws that are holding them.

Even though the stator is new, did you test it and also test for shorts to ground on it? What you're experiencing is real similar to the problem in the thread you linked to above. Except his only occurred when hot. He was also ready to blame magnetic fields problems.

Re: the tci, don't replace anything that isn't broken, except it won't do any harm to replace those four diodes. The Radio Shack TIP transistor recommendation will be on the hairy edge of how much current it's rated to handle. I calculated that once. The most important thing is to examine all the solder joints. I used a 10X magnifier to examine mine.


P.S. The man in the link, he replaced his stator and pickup at the same time so we don't know which was actually the problem.
 
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