Gone to the Dark Side - Ducati 860 GT

[Lannis]

A mate of mine has a '76 900SS that he rides almost daily. Even takes it on dirt when he goes camping! We keep telling him that he's crazy and should get a second bike but he loves riding it so much that he just doesn't care.

That's a happy, centered rider right there!

He loves riding it, he's happy with it, he's bonded with it.   Bugger the cost; and I'll bet what you like that he's spending LESS on Ducati parts and depreciation due to wear than most of us spend buying the new bike-of-the-year because we're not ever really happy with the one we have, eating the depreciation every day whether we're riding it or not ....

Lannis

[canuck750]

You can straighten the threads with a thread file, if you determine what pitch the stem is.

I tried for a good long while with my eight face thread file, I just can't seem the get the flat spot out enough to allow the stem nut to freely spin. I had disassembled the front end and regressed it before I totally stripped the bike and all was good. I am guessing the lower triple took a good fall and landed on the tip of the stem. I can get a thin jamb nut to spin on with some work but not the deep stem nut. Ordering some Chinese dies this morning, shipping is free. I may have to press the stem out of the lower triple and put in the lathe to check if tis out of round.
Stuff happens as they say

[canuck750]

A little progress this week, emptying out a few more bags of parts,

cleaned up the Aprilia signal lights, buffed up the aluminum with rouge polish, had the steel parts zinc plated or chromed



New rubber grommets and steel sleeves for the tail light bracket



I powder coated the rear bracket and save the original CEV tail light assembly



I made up a sub harness for the tail light and signa lights and used pvc tubing from British Wiring

I found a pair of the stock air boxes, getting rid f pod filters and going stock

cleaned up the fuse box, found a NOS lid and reused the regulator / rectifier



A repro muffler homologation tag



Rear half of the wiring harness hooked up

I bought a used dash, it was cracked but the idiot lights are all good, swapped them to the repro dash





Smiths gauges in the mail today to be restored by Andy at British Cables in Medicine Hat Alberta

Repro foot peg rubbers and new chrome springs from Eurotrash on Ebay

New intake valves arrived from Australia on Friday, dropped them off at the machine shop on Saturday, hopefully I get the heads back in a couple weeks

[Antietam Classic Cycle]

 

[jas67]

Where did you get the repro foot peg rubbers?
Do you know, are they the same as 750GT?

[canuck750]

Where did you get the repro foot peg rubbers?
Do you know, are they the same as 750GT?

Bevel Rubber our of Australia. Not sure if the 750GT are the same but the Bevel Rubber guys will know

[SmithSwede]

A mate of mine has a '76 900SS that he rides almost daily. Even takes it on dirt when he goes camping! We keep telling him that he's crazy and should get a second bike but he loves riding it so much that he just doesn't care.

I love this guy!  That’s the ticket.   He’s not crazy.   These machines are meant to be ridden, and loved on, and appreciated, and then ridden some more.  Like your dog wants to go for a walk, or swim, or catch a frisbee.

Good for him that he rides what he loves to ride. 

Kindly post a few pictures of this mate of yours on his Duck.  I’d really enjoy that. 

[Tusayan]

I don’t know if Keith Hale is still riding his green frame 750SS to work.  I remember seeing it years ago at Laguna Seca, looking slightly scruffy and parked in the dirt.

https://www.motorcyclistonline.com/1974-ducati-750-super-sport-me-my-bike/

750 and later GT footpeg rubbers are the same and are available here and there, a Google search shows several retail sources.  As mentioned above, Bevel Rubber makes them and a lot of other good stuff.

https://bevelrubber.com.au/cart/index.php?main_page=product_info&cPath=4_16&products_id=12&zenid=5l1rmmlj505ruu3cugq15g6175

[Chuck in Indiana]

*Really* nice attention to detail.. Attaboy.

[canuck750]

I had the one original Brembo disc measured up, there was a deep rust groove on the back side of the rotor and too deep to turn the rotor.

Bevel Heaven sent me a pair of new Brembo rotors, not cheap but I decided to add a rotor and go with a pair. The new rotors arrived bare streel, I used my DIY Eastwood powder coat gun to apply a coat of flat black powder. Eastwood sells the heat resistant masking tape as well as powder and the electrostatic gun.

Masked and washed clean with acetone.



A light coat of powder applied with just a couple psi pressure



Flip the rotor over and dust the other side then into an oven heated to 390 F for twenty minutes



Remove from oven and let cool



Then peel off the masking tape



I use an old used wall oven that I fit into a simple 1" HSS frame, I get these ovens for around $50 or less and when they die on me I just pick up another used one on Kijiji.

DIY powder is so easy, no fumes, easy clean up, super durable finish and cheap once you invest in the powder gun and a simple oven.

[Antietam Classic Cycle]

 

[SmithSwede]

This is great stuff.  Can’t wait to see it all come together

[Lannis]

Did you actually hand-cut all those gores in the tape so that it would go on without bunching and wrinkling?   Or is there tape that's made to lay down in a circle?   

This is a great illustrated narrative.

Lannis

[canuck750]

Did you actually hand-cut all those gores in the tape so that it would go on without bunching and wrinkling?   Or is there tape that's made to lay down in a circle?   

This is a great illustrated narrative.

Lannis

I just lay the strips of tape down with one hand and trim them with a sharp xacto blade around the outer edge. Once I have laid down the whole surface I scribe cut the inside circle using the lip of the rotor surface as a guide. Only takes about 10 minutes to mask both sides of a rotor. The tapes is laying on top of the lower piece, just straight sections. I just press down the tape with the smooth plastic handle of the knife.

This is the heat tape I use from Eastwood, I have a couple widths for different jobs

https://www.eastwood.com/hotcoat-high-temperature-polyester-masking-tape.html

The powder gun I have is the cheap one Eastwood sells, I have had it for at least seven years and it still works great

https://www.eastwood.com/eastwood-original-diy-powder-coating-gun-starter-kit.html


If you haven't tried powder coating I urge you to give it a shot, no runs or drips, no fumes, and super tough finish. The smallest air compressor will be fine, only 2 ~ 4 psi required.

Residue powder just sweeps up.

[jas67]

Wow, looks great.    I need to get a powder coating setup!
I should also add a second disc to my 750GT.   Funny, I was just out in the garage last night looking at the mounting tabs for a second caliper, contemplating adding a second disc.   Now would be a good time, as the single rotor it does have is a little warped, so, I need to buy a new one anyway, might as well just get two.

[canuck750]

The bike shop called to say the tires were in and mounted on the wheels. I went for Continental front and back.

First to get the rear brake assembled, new bearings in the hubs.



the drum spreader I made years ago for my Eldorado rebuild still comes in handy



and the sprocket carrier, rims have been re-chromed and Buchanan's made me new stainless steel spoke kits.



rear wheel mounted



I saved the original brake cable with the stop light switch

Front fender on



I need four new front disc carrier through bolts

installed a new steering lock

[Chuck in Indiana]

Lovely. 

[canuck750]

Lovely. 

Thanks Chuck, I am really enjoying getting to know this Ducati

I bought a cheap die off Ebay from China for under $20 (free shipping), there was a flat spot on the stem that needed to be recut

After a couple passes off and on the stem was good

The repro Ceriani top stem nut is a 'tight' fit, had to oil it and work it on and off several times. The O.D, was also too big, turned it down in the lathe

Top clamp fitted, stem nut set and steering damper back in place

and the underside of the friction damper

Picked up a set of four new M10 x 100 bolts and nylocks to secure the twin rotors

One caliper rebuilt,

I found a RH used twin bleeder that I need to rebuild. I need to order the rubber spacers that fit into the steel brake line guides

A rolling chassis



A very unsporting pair of original wide handlebars have been re-chromed, should be very comfortable for my rigid back, the switch wires pass neatly through the bars, might be fun getting the bundle of left hand switch wires through.

I dropped the seat pan, original foam and repro seat cover off at an upholstery shop today, hope the repop is a good match.

[smdl]

Really enjoying this, Jim.  Such a beautiful job!

Shaun

[canuck750]

Really enjoying this, Jim.  Such a beautiful job!

Shaun

Thanks Shaun, its sure different from a Guzzi!

[s1120]

I love the color of those fenders. Cant wait to see her back together!

[canuck750]

Switch gear went on today, I found a complete NOS left hand perch and switch, only difficulty was threading the wires through the handlebars, I cut off the molex tips, threaded the wires through then slid the pvc sheath over from  the bottom and crimped new molex connectors on.

I found a used left hand switch holder / throttle assembly, cleaned it up and powder coated the alloy casting, a NOS switch (Aermacchi uses them, priced right ie. cheap) on Ebay, The re-chromed bars are now thicker so I reamed out the plastic throttle slide with an adjustable reamer in my lathe, hand spun the reamer holding the throttle tube, worked great.

Same deal with the electrical, cut off the molex and sent the wires through,

I bought a repro ID foil but its not identical, the 'right' ones are out of stock, this will do for now,


I found a good used set of Smiths instrument holders, lucked out on Ebay and got them for cheap.

Fitted new brake hoses I had made up locally


Installed the headlight bucket, front signal lights and reflectors


Now to figure this mess out!


The original relays sit inside the headlight bucket, they are in poor shape and I would like to fit modern relays, this is the electrical diagram I recreated in AutoCad

Now I sure could use some help with this wiring diagram and fitting new relays

The relay(?) drawn below the headlight - can I fit a standard relay here?

The wires are:

Green to headlight
Black to ground
Green/Black (handlebar switch)
these three wires are joined together: White (fuse)-Yellow/Black (ignition switch) - Brown (handlebar switch)

Can someone please explain to me what terminals I would connect these wires to on a new relay?

Next mystery:

Looks like a Horn Relay?? (drawn above the headlight on the diagram)

Green wire to the Horn city/country switch on the dash
Brown wire to Horn city/country switch on dash
Red to left hand handlebar Horn push button

Can I fit a modern relay and if so please tell me what terminals I connect these wires to?

Last mystery,

There is another device (relay??) that has two green wires from the ignition transducers, a blue wire to ignition, and violet to the right hand kill switch.
Is the device a relay or some other kind of device?

Thanks in advance for any guidance, did i mentions I really struggle with all things electrical?

[jas67]

Wow, looking great, Jim.   I LOVE the orange paint!

Are you sticking with the stock master cylinder with the second caliper up front?
Also, does the second rotor just go right on the hub and line up with the second caliper, or is a spacer required as it was when I added the 2nd disc to my Eldorado?

That front end looks to be the same as my 750GT.

[canuck750]

Wow, looking great, Jim.   I LOVE the orange paint!

Are you sticking with the stock master cylinder with the second caliper up front?
Also, does the second rotor just go right on the hub and line up with the second caliper, or is a spacer required as it was when I added the 2nd disc to my Eldorado?

That front end looks to be the same as my 750GT.

Yep using the stock Brembo master cylinder for dual discs, it was reportedly too much for a single caliper but better with a pair - its the same master cylinder and caliper set up on my Laveda SF and Guzzi 750S.
The right hand caliper bolts right on to the stock fork leg, it was designed  to take a pair and was stock on the electric start 860 GTE.

[jas67]

Yep using the stock Brembo master cylinder for dual discs, it was reportedly too much for a single caliper but better with a pair - its the same master cylinder and caliper set up on my Laveda SF and Guzzi 750S.
The right hand caliper bolts right on to the stock fork leg, it was designed  to take a pair and was stock on the electric start 860 GTE.

Thanks.
I know the 750 Sport and 750SS both had dual discs up front, so, I figured they just used the same hub and fork across the board.
I think I'll be adding a second disc over the winter.   It definitely brakes better with a single than the Eldorado did with a single, but, it'd be nice to get it closer to braking like a modern bike.

The stock master cylinder on the Eldo was WAY too big for a single caliper, require a LOT of force to actually stop the bike.

[Muzz]

Looking fabulous Jim.

I just love your rebuild essays.  You do superb work.

[canuck750]

Thanks Muzz!

I dropped off the powder coated seat pan, original seat foam and a reproduction seat cover on Friday noon, got a call today its done! wow talk about fast service.

What a funky design... so 70's Italian, sharp edges abound

I got the seat cover on Ebay, Thailand supplier$60.00,  came with the strap as well, nice quality, they sell complete low back style seats as well


Rubber bumpers pads (rectangular and round style) from Bevel Rubber in Australia

https://www.ebay.com/itm/DUCATI-GT860-GT860-860-GT-SADDLE-SEAT-COVER-ZALA/223727502967?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649



I found a seller on Ebay listing two of the removable and always missing seat hinges + a latch mechanism


And the Smith gauges I mailed off last Monday are restored and on their way back to me, should have them by the end of the week.

Now if only the machine shop could get to the heads......

[Big_Jim59]

I built a Ducati 860 GT out of three parts bikes before I knew that no one wanted them. It was actually a really good bike. I even did a track day on it. It was slow by modern standards but fun as heck. I gave it a rattle can paint job in black but it was rubbed out between coats and it looked pretty good. I painted the tank badges gold. By the way, it was a non-desmo bike that used hairpin valve springs like a Manx Norton.

[canuck750]

By the way, it was a non-desmo bike that used hairpin valve springs like a Manx Norton.

The 860 / 900 GT / GTS were the last of the non-desmo bevel twins. I think the whole Desmo thing is over rated, most all other manufacturers figured out how to effectively close a high reving valve train with better springs.

My 860 GT has conventional valve springs.
 

Were hairpin springs a performance option in the 70's?

[Big_Jim59]

I stand corrected. It was my Ducati 350 single that sported hairpin valve springs.  Time plays tricks with memory. My Ducati 860GT was fun and dead solid reliable. My Ducati 350 was great once i got the Mikuni carburetor dialed in.