• 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.

1977 LM 1 dual plug coil wiring

J

Jonathan Seymour

Just got it firing!
Joined
May 20, 2016
Messages
4
Location
New Rochelle
Hi,
Anybody out there know what the wiring diagram looks like to wire up Dyna black 5 ohm coils on a 1977 LM! that was dual plugged but never wired. Presently the bike is wired for one plug each cylinder, the machine has a Dyna electronic Ignition. Thanks
 
All you do is connect a dual plug coil to the dyna and connect the HT leads to each plug. You got the right coils - the dyna has a history of failing with 3ohm coils that dyna originally recommended.

I highly recommend dual plugging -it will produce a bit of measurable extra power but more importantly help with detonation- but there are some things you need to know.
1, You have to recurve the distributor so you have about 6 degrees less advance at full advance. you can keep the fixed advance at the same amount as factory. This will add a bit of power and reduce detonation which is a problem with the lemans 1 running modern fuels.
2. If you haven't already checked piston to plug clearance - there is not a lot of space in there and it is easy to get plug piston interference. I've seen some jobs where the plugs needed to be indexed to avoid damage.
3. Use NGK plug caps - either put the resistor in and use non-resistor plugs or the other way around. When they are new it usually doesn't cause a problem to run resistor plugs with caps- it can cause problems as the plugs age. They are cheap and way better than the original Bosch - which won't fit on the 10mm plug anyway.
 
Agree with all of what Chris told you except about using resistor plugs with resistor caps. I've run this combination previously for nearly 50K miles with no issues. I only changed the plugs (Iridium) as I was feeling guilty running them so long. Also it wouldn't hurt to retard initial timing a couple degrees as the flame front will progress more rapidly with dual plugs.
 
" I've run this combination previously for nearly 50K miles with no issues."
Hi John.
I suppose it depends on the total resistance - I think NGK has three different values for the cap resistors plus whatever the plugs are. I found this on one bike a long while ago and it had me scratching my head for a while. With modern iridium plug you will probably never see it. Plugs have really evolved since Champions were the popular choice.

Really the resistance is only there to suppress RF - it doesn't help with the spark AFAIK.
 
Thanks Chris and John for the info. So when I mount the coils, sitting on the bike, the left coil handles the left cylinder and both primary and secondary spark plugs originate from the same left coil and same for the right side? Reason I ask is that on my 1978 BMW R100RS that is dual plugged, the secondary plug is operated off the opposite side. It always seemed odd to me that on the BMW the left side coil operated the primary left side plug but the second HT lead on the same coil goes to the right side secondary plug. Thats the way it was when I bought it and it has been running strong for 15 years.
 
"So when I mount the coils, sitting on the bike, the left coil handles the left cylinder and both primary and secondary spark plugs originate from the same left coil and same for the right side?"

Yes. You can do that with the BMW because it is a flat twin, One cylinder is firing and the other is on induction - the spark on the induction side being a wasted spark. It lets the mfg use a single double ended coil for single plugged motor and no distributor - just a contact breaker driven by the front end of the cam. The only problem with the system is that the current flows in reverse on one plug which shortens its life. I had a citroen 2cv with this system and every 8k it needed new plugs like clockwork.
 
Chris R said:
Really the resistance is only there to suppress RF - it doesn't help with the spark AFAIK.
Click to expand...

Yes, only for suppression of RF. Didn't really need it for bikes running points, but the RF suppression may be of value for electronic ignition systems and fuel injected computer controlled machines. Then there are those that want to run a radio ....
 
John,
So on the LM,1 run the the primary and secondary HT leads out of the coil that operates and corresponds to the left and right cylinder correct?
 
On a Guzzi there is no waste spark. Both left high voltage leads go to the left side, and both right high voltage leads to the right. Coil control circuits are the same as if single plugged.
 
Take a look at my recent coil post image. If not enough, I'll take more pictures. Couple days...
 
You must log in or register to reply here.
Back
Top