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Thread: 860GT Resurrection ignition and charging questions

  1. #1
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9

    Default 860GT Resurrection ignition and charging questions

    Hi all, Iím currently resurrecting my old 860GT and have a few questions. Although itíll stay looking like an 860GT Iím replacing some of the old, crap bits with more modern replacements. Iíve got the switchgear, brakes and carbs sorted and now Iím on the ignition and charging. It currently has a Lucas Rita that works perfectly well but I want something more modern and less obtrusive. The choice seems to be between Sachse and Silent Hektic. Both look very similar and from what I can tell both work pretty well. Iím currently drawn to the SH because itís cheaper and comes as a full package complete with coils. I think I might have to remove the flywheel though? Bike came with electric start; I removed it and found a kickstart casing back in the day but canít remember what else I took off. The original ignition is probably still inside. Any thoughts on ignition choice?

    I also want to replace the reg/rec; once again it works OK but itís 45 years old and has been in a damp garage for most of the time. Is this the sort of thing I need?

    https://www.electrexworld.co.uk/acat...88-860GTS.html

    Any help or advice gratefully received. Iím located in Belper Derbyshire btw (for now).

    thanks

  2. #2
    Join Date
    19.12.2005
    Location
    Forfar, Angus
    Ducati models
    Supersport 939, 907ie
    Other bikes
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    9,010
    I'm not in a position to advise on any of these ignition systems but they are both highly rated. The original ignition generator should be behind the flywheel.
    The Electrex reg/rect should work fine but you won't need the white wire which I believe is for a charge warning light. If your alternator is of the 3 wire type with two yellow and one red wire, connect the 2 yellow wires to the yellow wires of the regulator and leave the red disconnected with the end insulated.

    Old enough to know better, young enough not to care

  3. #3
    Join Date
    14.06.2014
    Location
    Essex
    Ducati models
    900S2
    Posts
    159
    I can only endorse what Derek said; both those ignition systems are very good, although the Sachse is by far the more popular, possibly because it is more commonly sold outside Germany. I'd be wary about having to dispense with the flywheel though, bevels have a very different character to the belt engines and most of that is down to the weight of the flywheel on the bevels.

  4. #4
    Join Date
    23.11.2018
    Location
    Near Vancouver, BC, Canada
    Ducati models
    81 MHR
    Posts
    32
    I just read the Sachse instructions for your bike and you are correct, the combo flywheel/ignition trigger is replaced with the aluminium Sachse trigger wheel. On my 81 MHR, I went with Sachse, Dynatek coils and HT leads, NGK plug caps and a Shendingen regulator. The instructions for set-up are a little different between our bikes but I can state that for my bike, it was really easy. If I recall correctly, the Sachse system has zero advance at start to make the bike easier to start and prevent back-firing so losing the inertia from the original flywheel may not be an issue.

    I did not use any special tools to determine TDC, just a chopstick in the front pot plug hole. The Sachse instructions for the GT860 neglect to state that the piston you are starting with for setup is the front one.

    My system has been flawless since I installed it. First kick start-up maybe 9 times out of 10, I'm sure the 1 time I kick twice is because I did not tickle long enough.

    If you need any help installing the system, just ask.

  5. #5
    Join Date
    23.11.2018
    Location
    Near Vancouver, BC, Canada
    Ducati models
    81 MHR
    Posts
    32
    The Sachse electric start system is different from the kick start one. If you go Sachse be very careful; how far did you go with the removal of the electric start? If you simply removed the e-start parts but still have the original flywheel then the original flywheel is modified by removing and replacing magnets and then put back in for the e-start model. The Sachse instructions are on their website for all models.

  6. #6
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9
    Hi there, a bit of a delay due to various stuff but returning to this now. I've looked at the Sachse instructions and the ES and KS versions are indeed different. As the extent of my removing the ES is external - casings and electrics - I assume underneath it has the flywheel described. Is there any disadvantage to just getting the ES version? Does a KS GT have a different flywheel or doesn't it have one at all? If I got the KS version could I remove said flywheel or would I need a different one? I can't find a KS parts manual to look.

    As an aside I've decided to completely rewire from scratch. I'll let folks know about it if interested.

    TIA

  7. #7
    Join Date
    19.12.2005
    Location
    Forfar, Angus
    Ducati models
    Supersport 939, 907ie
    Other bikes
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    9,010
    You can download a parts list for the kickstart model from here

    Old enough to know better, young enough not to care

  8. #8
    Join Date
    14.06.2014
    Location
    Essex
    Ducati models
    900S2
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    159
    Both the ES and ES GT's have flywheels, but the KS one is just a plain recessed one that fits over the ignition stator; the ES version has teeth machined into it to allow the engine to be spun by the starter. I don't see why you could not use the ES flywheel, although it would be a better solution to find a KS flywheel and get rid of all the ES paraphernalia.

  9. #9
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9
    Thanks for the replies. I've had a (email) chat with the guy from Sachse (very helpful, perfect English). With the KS version, you remove the flywheel and replace it with the Sachse 'magnet disk', mounted on the primary gear. With the ES version, a thinner magnet disc is instead mounted inside the flywheel. The thinner magnet disk is the only difference between the ES an KS versions.

    So I can either (1) retain the flywheel with redundant ES teeth and get the ES version or (2) ditch the flywheel and get the KS version - which is what everybody else with a KS Sachse will have done. There doesn't seem to be an option to retain the KS toothless flywheel.

    Looking at the KS GT parts diagram, the original flywheel looks more like a mount for the triggers rather than anything substantial. The ES one is a bit more beefy obviously. I'm inclined to ditch the flywheel like all other Sachse KS installations will have done - one less bit whirling around on the end of the crankshaft sounds like a good thing.

  10. #10
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9
    Right then, rewire is almost done and I have battery, ignition switch, lights, brake lights and horn all up and running. I've used modern wiring and components and completely ditched the original wiring design.

    So ignition/charging next. I got the Sachse KS version in the end. It looks well made an the instructions are very clear. Everything is off and waiting for it to be fitted. The bit I thought would be the hardest - getting the flywheel off - was actually easy. As couple of light taps with a hammer and wooden drift and it just fell off. The hard bit was separating the flywheel from the primary drive. In the end I had to get three of the six screws drilled out.

    I've got the dyna coils connected up and the rest of the Sachse fitting looks easy enough. The bit I'm stuck with is the reg/rec connections. I have an Electrex RR51 unit and my alternator has 2 red and one yellow wires. The Electrex site says this:

    For models with 2 x Yellow and 1 x Red generator wires, please use type RR51, with both yellow
    generator wires connected together as 1 phase wire to the RR51, and the red generator wire as the
    second phase wire to the RR51.

    However, Derek above says this:

    The Electrex reg/rect should work fine but you won't need the white wire which I believe is for a charge warning light. If your alternator is of the 3 wire type with two yellow and one red wire, connect the 2 yellow wires to the yellow wires of the regulator and leave the red disconnected with the end insulated.

    That looks different. If you are there Derek, any further thoughts on this? What are the three wires I have for as opposed to the more common two? The only wiring diagram I can find with a 3 wire alternator is for a "coil ignition model" and the red wire comes out of the alternator and just joins up with the reg/rec output.

    thanks

  11. #11
    Join Date
    19.12.2005
    Location
    Forfar, Angus
    Ducati models
    Supersport 939, 907ie
    Other bikes
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    9,010
    The alternator is centre tapped and connected to the charge circuit something like this -


    Although I think on the GT the centre tap actually goes to the positive side and not to ground but the idea is the same.
    So you can connect the 2 windings in parallel by joining the 2 yellows and connecting the RR1 across the red and the combined yellows.
    Or you can connect them in series by connecting the RR51 across the 2 yellows and leaving the red unattached. I've seen both set ups and both will work although the series connection will result in a higher voltage with a lower current going into the regulator.
    Do as Electrex suggests and if the regulator subsequently fails they can't blame you.
    Last edited by Derek; 29.04.2020 at 02:32 PM. Reason: spelling

    Old enough to know better, young enough not to care

  12. #12
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9
    Thanks Derek, that makes sense. TBH I'm more worried about the reg/rec failing and frying the Sachse unit but I'll do what Electrex says.

  13. #13
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9

    Default Woodruff key installation

    Just trying to put all this back together. I have my new Sachse magnet disc mounted on the primary gear and ready to go in. The whole thing slides on and off easily but I need to get the woodruff key in and it's a tight fit. Should I slide the gear on, line up the slots and try and push/tap the key in the resulting hole or try and slide all of it in together? I've lightly sanded the key and cleaned up the slots. It wasn't particularly hard to get the old flywheel off so it shouldn't need a lot of effort to get it back on. Any tips appreciated.

  14. #14
    Join Date
    14.06.2014
    Location
    Essex
    Ducati models
    900S2
    Posts
    159
    It is usually easiest to insert the key in its slot and then slide the flywheel over it.

  15. #15
    Join Date
    07.04.2009
    Location
    Inverness
    Ducati models
    Bevels, Belts & Gears
    Posts
    501
    Yep all together and a tad of grease on the key to make it slightly sticky then pray it sits correctly
    The difference between stupidity and genius is that genius has its limits.
    - Albert Einstein.

  16. #16
    Join Date
    02.07.2018
    Location
    Belper
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    9
    thanks chaps, I'll give that a go.

  17. #17
    Join Date
    23.11.2018
    Location
    Near Vancouver, BC, Canada
    Ducati models
    81 MHR
    Posts
    32
    kevm: Sorry, I've been away a while. Different bike (81 MHR) but similar issues. I found a description of the fit of a Sacshe system to a 900 twin somewhere on the internet, I think Bevel Heaven, where the fit of the trigger "wheel" was discussed. Once I had the parts, I could see that it would be easy to tap the trigger on the end of the crank with the key in place but it would be impossible to remove the thing in the future; too tight a fit at the backside to get in a tiny puller. I used a tiny file and a blue Sharpie to very gently adjust the fit of the trigger to the key so that it was a tight fit on but I was also able to pull it off.

  18. #18
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9
    I think because I have a KS version it will be OK because it does away with the flywheel. The Sachse magnet is attached directly to the primary drive and there is room to get a puller between the two and pull both off. I hope so because it's on now via a few light taps with a rubber mallet! It all lines up nicely with the clutch drum so need to tackle timing now.

  19. #19
    Join Date
    23.11.2018
    Location
    Near Vancouver, BC, Canada
    Ducati models
    81 MHR
    Posts
    32
    Hi kevm: here's a short write up for my bike. Setting up the timing was surprising easy. http://forum.bevelheaven.com/viewtopic.php?f=19&t=5415

  20. #20
    Join Date
    02.07.2018
    Location
    Belper
    Ducati models
    860GT
    Posts
    9

    Default Started !!!

    I followed all the advice, links, instructions and got the ignition in and generating a nice fat spark at the right time. Clutch and casing on, oil checked and rebuilt carbs (thanks to Ducati Paddy) back on. I eventually plucked up courage to kick it over and on the 3rd kick it spluttered, backfired and settled into a much too high tickover. A bit of playing around with throttle cables and idle screws is needed but we seem to have a runner. It's been about 10 years since it last ran and I (probably unwisely) completely rewired it, installed the Sachse and had the carbs done all at once so am quite chuffed it actually works. Still a few things to do/check before it's rideable and more before it's as I want it but it's a step in the right direction to another (standard looking) 860GT being back on the road.

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