• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

Weird charging issue on Le Mans II

JFerg

Just got it firing!
Joined
Oct 30, 2008
Messages
8
Location
Melbourne, Oz
I've just read through Levoz' thread below, but I have a different issue.

I've just put my Le Mans II back on the road after a major (200,000km) maintenance spree. This included new alternator brushes. Despite the bike only being apart about 3 weeks, I had to flash the alternator to get it to start charging. Then all was good until this week.

2,000km since the rebuild completed, all is fine with the slight qualification that I need to hit 4 grand after a start for the charge light to extinguish. No biggie, and not a problem. This week I was out for a ride with some mates. We stopped at the pub for lunch. After lunch I led out, then waited a few hundred yards away for everyone to get organised. When I re-started the engine from there, the charge light did not extinguish. I was a bit peeved and started calculating how far I'd get, given I was 100 miles from home; but twenty minutes later, during normal riding, the light went out and the voltage came back up. At the coffee stop and at four further starts after that, it would not extinguish.

So I put it up on the bench. Everything is fine. Brushes are bedding in nicely, not snagged, connections are all good, a substitute new (out of the box) regulator made no change. In frustration I flashed the bastard again and guess what? Problem is gone again. Still on the bench and in disbelief, I reckon that I've made a further ten starts at least, over 5 days, and each time the light goes out and the charging kicks in at 4 grand the first time, under 1500 rpm thereafter.

The theory of flashing the alternator is that you restore the residual magnetism that ebbs away when the magnetic circuits are broken, which is what happens when you take the alternator apart and put the bits in a box. It's this residual magnetism that allows the alternator to start charging. The residual shouldn't be lost in an assembled unit (except maybe over a very, very long time unused) and certainly can't be lost in minute, yet that's what seems to be happening.

Any and all wisdom greatly appreciated,

JFerg
 
It sounds like you have the Bosch charging system. You shouldn't have to get to 4000 RPM to get it charging. Rotors are a known week point. The voltage regulator varies the current to the rotor to change the magnetic field. Remove the regulator and bridge the connections at the socket to provide a continuous 12 volts to the rotor. She should charge immediately. If not, the rotor is suspect. Also I tin the connections at the stator with solder to make cleaner connections that won't corrode. Have you tested the stator? You should have 0.62 ohms between fields. Also the ohm reading for the rotor should be 6.9 ohms =/- 10%. To ohm the rotor, lift one brush then take the reading at the slip rings. Also be sure slip rings are clean. Clean with fuel or carb cleaner. If necessary it may be polished lightly with very fine sand paper (I would use 400 to 600 grit), not emery cloth.
 
Thanks, John. Resistance measures are all ok, but I have a new spare rotor and might fit it anyway. Slip rings were dressed before reassembly. I'll let you know what I find.

cheers,
JFerg
 
Interesting.
I have a very similar problem with my '80 G5 (Bosch).
Standing by for education...

Alex
 
Just plain weird. Bridged the regulator as John suggested, no difference.
Fitted new rotor......problem solved.
Only possibility that permits slow start, normal behaviour, an intermittent fault, and has an inverse relationship with engine revs is a slipring defect, probably a dry or not quite complete soldered joint to the slipring. While the rotor is open circuit and still spinning it will lose it's residual magnetism.
I have kept the old one, of course. I will throw it at the neighbour's cat.

again, thanks.
JFerg
 
Ahhh JFerg, THAT's what I failed to do..

Thanks for the posting.

here kitty kitty…

Alex
 
Back
Top