Little or no spark either side

[wwitten]

I swear this bike is going to be the death of me...one way or the other.

OK with all of your help have gotten through problem after problem and was actually riding for a couple of day, but was concerned when I slapped the battery charger on just to top her off and noticed the battery had low voltage and didn't seem to be re-charging enough.

Checked the battery while bike was running and didn't see any voltage increase while running at any RPM level. Went to the tech section read the info, pulled out the manuals and checked the alternator, regulator and rectifier. All tested within limits but the rectifier concerned me with the amount of corrosion and the red lead at the connector seemed like it might have fried a little at some time in the past. Cleaned everything up, retested, bike started up, checked voltage at battery and charging system seems like it now was up and running. Due to weather bike sat for a few days, but I checked battery and there was only minimal voltage drop. Weather turned good, so I tried to start her up, but no go. Finally checked the plugs and found little if no spark. By this time battery was getting weak so I slapped on the battery charger and within a few minutes, cloud of smoke arose from the old girl. Pulled charger and investigated. The ground wire from the rectifier fried from the rectifier all the way to were it joins the other grounds in the wiring harness under the tank near the coils.

So OK strip the wiring harness replace the bad wire, pull the rectifier, and build a new rectifier using the Radio Shack method discussed in the posts here. Just installed the mod and still little or no spark to plugs.....Guessing somehow I fried my coils? Will check later and see how to diagnosis, but any other thoughts

 

[jd750ace]

Check your fuses for information. Get a new battery. Test your coils. Matter of fact, test everything again. Might not have fried anything. Treat it like a plane crash. No guesses. Collect facts and analyze.

 

[TwoJugs]

guessing this is a ponits condensor coil bike? Check voltage with a small load on the battery, headlight on, bike off. See how much of a voltage drop you get. A battery can show 12V but have no capacity in it (amps) and a small load can drop the volt reading pretty low.

 

[XSLeo]

With a separate reg and rec I assume you have a points bike. So assuming this check for voltage at the red/white wire where the coils plug into the harness. It should read the same as battery voltage, no less than .2 or.3 volts less. So when you turn the key on and engine stop switch to run, check the battery voltage and compare this to the voltage at the coils.
If too much voltage drop it can often be dirty switches, either or both the key switch and engine stop switch. Most key switches can be removed, taken apart and cleaned. All engine stop switches can be taken apart and cleaned.
Once you get full voltage to the coils your spark may improve. Good, clean properly adjusted points help too.
The ground wire you burnt up has no effect on the coils. If they are the 30+ year old stock coils then they are weak. They were weak when new and 30+ years hasn't made them any better.
There are lots of better coils out there. A bit of searching on here will lead you to how to upgrade.
Leo

 

[wwitten]

OK so I went through the whole bike over the last two evenings, charging system, ignition system etc., about the only thing I didn't check was the valves and timing chain as those would have nothing to do with the plugs. Everything was within spec.

So I started measuring voltage from the battery through every connection up to the main switch and discovered a 1+ voltage drop. Great, dissembled switches ohm them and cleaned even though no major resistance noted. Reassembled and still same voltage drop. Disconnected everything and reconnected each wire one at a time until I found that the main brown lead was pulling voltage down by 1+ volt. Disconnected everything on that run and found the regulator seems to be the culprit.

Double checked reg on and off bike, and all resistance values in spec, but as soon I reconnect it voltage drops. Got to assume that is not right. Regulator shouldn't be pulling that much current, should it? Can put on all the lights, turn signal horn etc. with no voltage drop other than a few hundredths. Does this sound right?

If so have already purchased the I believe a Chrysler auto reg as discussed in other post. If I follow that, I should replace (3) alternator screws with nylon screws. ground the base of the regulator, and connect the brown and green leads as noted.

 

[retiredgentleman]

Its not your regulator that's pulling down the voltage, its most likely the alternator rotor.

The regulator supplies the current to the rotor. Sometimes the rotor shorts out part of its windings, which produces low resistance, which then draws extra current. This also results in poor or no charging of the battery.

You should remove both brushes, and measure the resistance from one slip ring to the other slip ring, also measure from one slip ring to rotor frame.
Here is a link with details:
http://www.xs650.com/forum/showthread.php?t=10561

 

[wwitten]

Retiredgentleman,

Your right as many times as I have checked slip ring to slip ring before and got around 5ohms...now suddenly down to around 2.5 ohms.

Assume upgrading regulator won't impact this enough until the rotor is repaired/replaced, and no way will I be able to get enough spark to plugs or even check without doing so.

Oh well, maybe next year I'll get her out on the road. Oh I said that last year too.

If it wasn't for the fact that I've got to much invested to quit now...plus I'm just not a quitter, guess I'll start searching for what to do next.......

Thanks

 

[aldo5468]

Retiredgentleman,

Your right as many times as I have checked slip ring to slip ring before and got around 5ohms...now suddenly down to around 2.5 ohms.

Assume upgrading regulator won't impact this enough until the rotor is repaired/replaced, and no way will I be able to get enough spark to plugs or even check without doing so.

Oh well, maybe next year I'll get her out on the road. Oh I said that last year too.

If it wasn't for the fact that I've got to much invested to quit now...plus I'm just not a quitter, guess I'll start searching for what to do next.......

Thanks

It's not difficult or time-consuming to replace the rotor. I just did it recently on my 650. Make sure you obtain and use the proper puller.

 

[retiredgentleman]

Rotor failure is common because of the age.

Here is a link to Custom Rewind. Everyone that uses their product has always had good results:
http://www.customrewind.com/

It would be a good idea to replace your OEM stock regulator with a NOS automotive regulator such as the VR-115. They are inexpensive and will control voltage at 14.0 to 14.3 volts. The VR-115 regulator works well with 1970 to 1979 years, because its designed to work with one brush at ground, which 70 to 79 use. Nylon screws are not required with the VR-115.

The chrysler regulator is for the 1980 to 1983 years.

 

[wwitten]

Aldo,

Thanks, yes rotor replacement, not that difficult with correct puller etc., just time/effort involved and the fact that riding weather up North is getting shorter and shorter with each passing day. Not a winter rider myself, don't have the correct gear.

Plus have some minor oil leaks, engine could use a good clean up, do I pull it and work on it this winter. If I do that do I strip in down and repaint frame. What other mods would I do? Damn my mind never stops.

Will look at the details for puller etc. and speak with local mechanic and see about referrals for local rewind service and check out others mentioned on this site and then make decision.

 

[wwitten]

Retiredgentleman,

Rotor failure I'm sure is not that uncommon at this age, but know that it was at spec couple of months ago even a couple of days ago when all this started. don't think anything I did could have cause failure, but I have be testing it in the garage with the alternator cover off. Hope I didn't suck something in to scrape the windings....oh well.

Did see on site references to Custom Rewind, but also some comments maybe older that their turnaround time and customer service was poor. Maybe corrected now, also maybe timing as many of the shops here are only busy a few months of the year and getting anything done during the "season" is never quick.

Also you said the Chrysler regulator is for the 1980 to 1983 years. Guess I jumped the gun and will have to see if NAPA will return/trade for the VR-115.

Thanks

 

[XSLeo]

You can unplug the regulator and continue the weak spark testing. You don't need to have it running to test the coils or work with the points.
As RG said the reg controls the current through the rotor. It draws about 2.5 amps. That's just a bit less than the low beam on the headlight.
You can just unplug the regulator and continue your ignition trouble shooting.
You can use the Chrysler reg you just need to do the three nylon screw mod. This requires you do a bit of rewiring but it works well.
You might find a good rotor online but they can be a crap shoot. Some one on here may have a good one.
And as you found they can go bad very quickly.
Leo

 

[wwitten]

Leo,

Thanks, was wondering if I could continue troubleshooting the spark issue as long a regulator was disconnected. I know that now with regulator removed I have same voltage less a couple hundredths at coils as at the battery. Surely didn't want to do any more damage.

The wiring on this bike leaves a lot to be desired as its using the harness from the 78 engine but all other wiring remains as in 74. Some color code differences, some routing differences. PO tore up a lot of the insulation on some of the connections, did some crapping soldering, taping etc. so I will need clean up as time permits.

I'm hoping that whatever happened while investigating/cleaning/repairing the charging circuit, and the noticeable voltage drain across the system, might be the cause of the low spark. Have checked coils/condensers/points/timing and they all seem OK. Will give her a try and see what happening. The ignition system was at least functioning well enough to start and run with no known issues prior to attempting to fix the charging circuit

Unless there is an overriding reason to use the Chrysler regulator over the AMC one, will swap at NAPA and go with the AMC one.