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Discussion Starter #1
My 1980 Darmah SS won’t charge the battery. It goes dead 30 miles or so in. The red charging light is always on. This is the model with a Bosch ignition.

When the original ignition switch broke, Bevel Heaven sold me one for a later model that has the headlight always on.

I don’t know much about electrics. Can anyone help me troubleshoot this and find parts?
 

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I don't know much about electrics either but here are one or two thoughts: Running the headlamp on all the time will not flatten the battery - I run mine like that and have no problem. I would guess that your regulator/rectifier has packed up, which they all do eventually, and this is why the red warning light is on.

Do you have a test meter? If you place the probes onto the battery terminals and rev the engine you will see if any charge is generated; a simpler test is to turn on the headlight and rev the engine from idle and it should show noticeable brightening.

I would expect that your regulator/rectifier is toast. They are readily available from Bevel Ducati spares outlets.
 

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Discussion Starter #3
Any ideas on how to troubleshoot and determine the problem? The rectifier is a $150 or so part and I’d hate to replace it just to find out that’s not the problem.
 

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On a bike that old, the rectifier is a good investment anyway and as for the price - is this a Concours d'Elegance show winner bike where you have to have oem everything? Get something modern for $50 new or less used and it will work more than fine.

I had a similar alternator to yours on my bike and got it rewound by a BMW guy in Denver to take it from about 175 watts to 300 - made a lot of difference on modern batteries and I live in a temperate climate unlike you. Yes, you should check and clean the main ground point before pulling out your wallet but non mosfet rectifiers just do not last as long as yours already has.
 

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Discussion Starter #5
That’s interesting. Any specific suggestions? Will any rectifier/regulator work? A Honda/Kawasaki/Yamaha part? Any particular spec or capacity? For instance, I use accessory solid state rectifier/regulators on all my British bikes. Would that work? And what does “non mosfet rectifiers” mean? I’m pretty uninformed on electrical matters.
 

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Here is a guy who can advise you:https://www.ducati.ms/forums/14-vintage/718563-900ss-regulator-mounting-question.html

You can test the regulator and alternator with a small voltmeter across the battery terminals, if the charge exceeeds 14 - 14.5 volts then the alternator is working but the regulator has failed. You will probably need a new battery as the old one will have been damaged by the overcharge.

A MOSFET regulator is new technology that controls the charge to the battery without producing heat. I fitted one to my modern Ducati a few weeks ago as a precaution, because of the reputation of normal regulators to pack up.

Check this out:https://www.electrexworld.co.uk/cgi-bin/sh000001.pl?WD=ducati&PN=Ducati-900-Darmah-900-GTS-900-Hailwood-replica-Regulator-Rectifier-RR51.html#SID=439
 

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I recently went all the way with a Sacshe ignition, DynaTek coils and a Shendingen regulator (https://www.roadstercycle.com/).

Before jumping to conclusions, give your wiring a really good inspection and make sure your grounds around the battery and regulator are all clean and conducting. Then move to your fuse box; again check everything and make sure all is clean and conducting. I have an old analog multi meter with a buzzer function for continuity checks. Love it; perfect for these jobs.

A very typical failure point is the insulation of the 2 yellow leads from the alternator at the regulator connectors end; I think the wires are too small in diameter and simply get too hot at the regulator plug end. When there's no insulation left, the exposed wires are not supported and can flex and break so check. I replaced the last 6 inches of wire with a slightly heavier gauge on my bike.

Next test the alternator output; disconnect the two yellow wires from the regulator and hook them up to a multimeter set on alternating current and anything over 100V. Start the bike and see what you get; alternator stators typically either work or don't, so if you see nothing, then either one or both of the wires is broken or the stator itself has a broken wire or short. Check each yellow for continuity to ground; you should not see any; if you do there's probably a short in the alternator stator. Alternator stators can be repaired so don't rush into buying a new one.

If you do see an output from the alternator and your yellow wires were good then the regulator is the next likely culprit. I'm pretty sure that all Darmahs have 12V, 28A regulators to handle the electric starter. There are some simple tests you can perform to test a regulator; just Google it. You will need a multimeter with a a diode test function. If your regulator is toast then you have the choice of replacing it with the same or going my route with a more modern Mosfet style but be warned; the one I got, a FH020AA, is slightly bigger than the original. I was able to fit it on my MHR on the same frame plate with a few tweaks. I'm not sure where the regulator lives on a Darmah. If you do go this route, tell me and I'll send you my wiring updates for this mod.

I should have started with the battery; if your battery is tired then you will have charging problems, starting problems and a weak spark. Weak batteries are often blamed for wrecking sprag (starter) clutches too. Batteries do not live forever and have a finite lifetime even when babied. You could take your battery to a local auto shop for a test; a good idea to put this possible issue to bed.

Please post back as you proceed and good luck.

Your Motopiat voltmeter looks like it is actually working. It's supposed to give you a "Gen" warning when the bike is running but not charging
 

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Discussion Starter #8
As at least one of you suggested, the problem was that the ends of the yellow stator wires were basically melted/broken/burned off. I replaced the top foot or so of each 16 gauge wire with 12 gauge and put it in heat shrink tubing, and when I rode it the red charging light went out and it ran just fine. The problem was so obvious I didn’t do any diagnostics, but this may simply be a temporary fix (hard to believe the rectifier would survive that much heat) and if so I will probably get the motsef regulator from the very helpful guy at roadstercycle.com. I want to thank everyone for their very helpful posts, I’m fine on mechanical but not so good on electrical issues, so I needed assistance.

I really enjoy this big Bertha of a 1980 Darmah SS. I have owned it since 1982–bought it from Jim Woods’ shop in Burbank, parked it at a friend’s shop in the San Fernando Valley, and rode it many thousands of miles on California twisties—all the Santa Monica mountains roads, and highways 33, 166, 25, 46, 41, 49, Tepusquet Road, Nacimiento Road, many trips to Laguna Seca, and a zillion more, and eventually moved it to Alaska to live in my garage when we started to have kids. Don’t ride it much anymore but truly love to hear the roar from the Conti’s and the 40 mm carbs again!! Thanks to all who helped!
 

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Discussion Starter #9
Oh, one other thing—the very helpful and informed guy at roadstercycle.com said he thought the alternator output was marginal for my “headlights always on” replacement ignition switch and suggested a relatively simple and inexpensive way to get it a little breathing room without rewinding the stator— replace the headlight with an LED light. Anyone have experience with that? Any idea what the best one is?
 

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True, the LED uses less power BUT - if it doesn't have enough it won't work at all!!!

I had my alternator rewound for more output, I might recommend the same and then replace all the wiring you have in the bike - esp the lights and starter circuits. There are some nice write ups in the supersports section, should be close enough to get the idea. Any loss from brittle wires you cannot afford when starting from so little juice.
 

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Discussion Starter #12
Anyone have experience with LED headlights? I’d like to try. On photos, how does one post them on here?
 

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Discussion Starter #14
I think I figured out how to post a couple thumbnails, they should be visible now. These are the only photos I have at this point, but I can take more and post if folks request. As you can see from looking at them, the visible modifications are very few and limited to a few details--simple Italian red paint, instead of the silver and blue with dashed lines and tiger decals, a smoke colored Gustaffson windshield, reversed fork legs to get the calipers under the steering head to improve steering, a custom color matched red Corbin seat, and Works Performance shocks, in a length an inch over stock to cut down a bit on fork rake, a Tomasselli 2 into 2 throttle, and stainless braided brake lines--and the nearly standard 40's and Contis. Otherwise, it is dead stock. One other little subtle adjustment, when I used to ride this in the tight California twisties, I dropped the forks in the clamps maybe an inch and a half or so to further improve its steering, but now I have it in Alaska and ride bigger roads, I have stood it back up so it steers in much larger arcs again.

On my electrical problems above, after fixing the regulator/rectifier wiring, I found one more defective very small diameter wire set--the circuit for the low tension side of the coil on the forward cylinder, which looks like maybe 20 gauge wire--that was similarly melted/burned up so I replaced that with larger wire, and I then encountered an almost comically challenging short somewhere, that resulted in the bike running with the high beams on, but not running if I switched on low beams--the low beam switch operated like a kill switch. As I mentioned above, some time ago my ignition switch died (the clutch cable hits it when I rotate the forks) so and I could only locate a newer "always on" switch, and I wanted to return to being able to turn the lights off, basically for starting, for battery conservation. Gowanloch Ducati in Oz was very helpful, and suggested simply disconnecting the headlight wires from the switch and joining them. I did this and--although I have not ridden it yet, knock on wood-- it appears this has it let me turn the headlights on and off, and also fixed my short so I can use high and low beams again. I anticipate the wiring problems will persist with the passage of time. If so, I will be back here, asking advice again.

What's interesting to me is when I bought this thing back in the early 80's, Jim Woods, the knowledgeable LA bevel drive Ducati dealer I got it from, recommended I buy a Darmah SS instead of a normal SS, since they came with far more reliable Bosch electrics and since I wanted to ride it a lot. He has been right over the 35 years or so I have owned this, but I am now beginning to encounter problems, not so much with the Bosch parts, but with the wiring loom, Ducati switchgear (but NOT the Nippon Denso switches), etc. But the trouble is definitely worth it, of all the motorcycles I own, this is the one that stops me walking out of the garage, every time, for one last look back, I really like this thing to ride, work on, and look at. I imagine a lot of you feel the same way about these older bevel twins.

Thanks again to everyone who gave me electrical advice, I appreciate hearing from you and sharing ideas.
 

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I love bevel Ducs, they are just so involving, and wish that I could buy another one, but I'm not paying today's prices. I wish that I'd not sold my 750, but I needed the money.

Jim Woods sounds like he was a really enthusiastic guy, I've come across references to his shop many times and Kevin Bracken's account of racing his bevel with the help of Jim was fascinating.
 

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Here's a link to my ignition project; lots of big, fat, 14 guage wires. The only thing that has changed since I wrote the detailed description is that I now feed the power from the regulator to the battery via my spare fuse slot fitted with a 25A fuse. This was a recommendation from Jack at Roadstercycle from whom I bought the Shendingen regulator.

New ignition system: need advice! - <-=- Club Bevel Heaven -=->
 
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