850T Electrics 1975

[eightiesguzzis]

Just about to pick up an 850T, Has been sitting for a while started up and once warm seemed to be good. Then went to start again......no more go! Slither of smoke rising from behind key/ignition. All original wiring, I am keen on installing an electronic ignition ASAP (I have on my 83 Lemans). I'm not as familiar with the round barrel bikes!

Are the electrics at least similar to an 83 MK3 Lemans (I'm familiar with them!) or should I throw the loom away and go lithium with keyless M-Unit?

Any electrical advise/previous experiences appreciated :)

[Frenchfrog]

Oxidation is the likely cause....the ignition switch is probably totaled due to oxidation build up inside making it overheat and the plastic then melting. MG cycle is your friend .You really want to go through all the loom and de oxidise after fitting a new switch.

[Old Jock]

Yup agree with FrenchFrog

Probably the ignition switch is toast, as start these things have to carry a lot of current.

You can modify the loom and install a relay to reduce the current the switch has to carry.

As far as a rewire and an M-Unit, it would depend on the state of the rest of the loom and how much cash you want to throw at it. Another slightly less expensive (and less capable regarding features, but still a good thing) is the PDM 60.

As far as I know without looking at diagrams most of these bikes have a near identical wiring layout. You can check out Carl Allison's diagrams hosted on This Old Tractor, Gregg Bender's site

[Kiwi_Roy]

Don't give up on the wiring just yet, what may have happened is the grease in the switch has dried out and gone hard holding the contacts apart causing a little heat.
If you can pull the switch apart you may find you can refurbish it with some fresh grease (Vaseline)
This is just another variation of Startus Interruptus., you could do a modification however the wiring on these old girls is pretty robust, nice and fat.

As John mentioned here is Carl's drawing
http://www.thisoldtractor.com/guzzi007/schematics/1974_850T_USA.gif
Trace the path of the power to the solenoid backwards through relay (23) contacts through fuse (33)/Fuse 2 to the ignition switch (38)/15/54 and red wire 30 all the way from the battery.
The instant you press the start button and the relay closes about 30 Amps will pass through that route so everything has to be nice and clean, I would certainly clean up the fuses and make sure everything is nice and tight.
You could as John mentioned add a relay to take the load off the switch if it's toasted the 15/54 contact, the contact 50 of the ignition switch is not heavily loaded and could trigger the coil of the relay.

The other switches (12), (13) & (14) will be a bit dry as well, you will be amazed how nice they feel with a bit of fresh Vaseline

Why upgrade to electronic ignition, it's worked for the last 45 years.
Please don't downgrade to Lithium just get a nice big AGM

Update
+1 for Greg Benders new looms as Perazzimx14 mentions
Perhaps add a 40 Amp in-line fuse in the red wire at the battery to prevent a catastrophic melt down if the old loom breaks down to chassis, think 200+ amps available to let out the magic smoke.
Yes similar to your LeMans

[earemike]

My T3 needed me to clean the contacts on the ignition barrel (cleaned up some earthing points at the same time).

Fixed my issues

[geodoc]

whether you have any luck cleaning the switch contacts to render it functional again or have to install a new switch, it's very much worth while to modify the switch so the system load goes through a 50A relay like so:



This mod makes it so your 'parking' light position is no longer functional, but I never used it anyway.





.

[eightiesguzzis]

Great and thanks all for the info and advise....

Are there no supporters of Lithium batteries and M Unit (for example) systems ? I certainly like the idea of upgrading 70's electronics to modern day, bluetooth connectivity etc. Revival Cycles has an example of an 850T completely rewired, at cost, however it has it's benefits as well.

https://revivalcycles.com/homegrown/lee-hathaways-1975-moto-guzzi-850T

[Old Jock]

My Magni based around an LM 1000's running gear has an M-Unit and there are a couple of folks on here running LiFe batteries with the Bosch electrics and say it works fine although I've never tried one myself in that particular bike.

I've ran/run LiFe in a later bike based in the Ducati Energia system and in a Ducati 1098. There are drawbacks with them and they need to be treated differently I posted on another thread about it here
https://wildguzzi.com/forum/index.php?topic=101198.msg1600007#msg1600007

As far as the M-Unit I have an early type one of the first series and it works great, but unless you're planing a custom rewire I would honestly doubt there is much to be gained. I've posted this picture many times and no doubt people are sick of the site of it but below is the M-Unit in my bike. I also helped another 2 or 3 on here with the wiring to install one, it's not particularly hard but takes a while if you are going to do it properly (well it took me a while). If you were doing it you could also upgrade the bar switches to pushbuttons too.



 

[Kiwi_Roy]

I don't have much imagination, I cant see what you would gain from being able to talk to a 45 year old bike from your phone.
Lithium batteries are amazing when you want to save weight I just think they add unnecessary complication AGM are also streets ahead of the original wet cell variety.

You asked if you should scrap what you have and start again, my approach was OK it let out a bit of smoke because the grease went hard but it really doesn't need much to get it going again, why start from scratch, are you planning a frame up restoration?
I didn't even suggest making the simple Startus Interuptus fix I usually advocate because the switch obviously needs attention anyway.

You can see from Johns stunning example what can be done with modern components but that didn't happen overnight,
Download a copy of his booklet, it's full of ideas.

Whatever you do document any changes so the next owner can figure it out.
I thought afterwards that you have a LeMans with electronic ignition maybe that's the way to go.
I certainly think modern blade fuses would be an upgrade but i haven't seen any multi fuse assemblies that I would trust, you will likely have to find something on the internet

I did something like Geodoc suggested to a California II

What part of Godzone are you from?

[Old Jock]

If you want to read that booklet I produced on some idea with Guzzi electrics it's here, Roy gave it the once over and corrected mistakes and made some invaluable contributions too

http://www.thisoldtractor.com/guzzitech.dk/gb_en_complex-technical_charging-around-the-circuit.htm

John

[Dave Swanson]

I just installed a wiring harness from Greg Bender on my 1000S.  It was flawless, and functioned perfectly.  I highly recommend.  I will be using them on my V700, and Convert also.

[Old Jock]

Stunning Dave simply stunning