1974 Ducati 750GT rebuild - unabridged edition
I’m still a newbie here, and this bike has been seen in a few places on the web before, (including this forum…) but this site seems to be friendly to picture-rich threads and project threads seem to be enjoyed, so I thought I’d do a little more in depth post on the rebuild of my first bevel Ducati. (I got it back on the road a few years ago, this is a retrospective as it were). I’ve got a couple single cylinder Ducs underway now, but progress is slow (probably because I spend too much time on the web) so I thought this one might be a better start. If it’s too much just tell me to shut up!
So… here's my 1974 Ducati "Roundcase" 750GT.
I bought it from a friend after a few years of “is it for sale? Is it for Sale? Is it for sale?” type messages. Finally it WAS for sale. I was in Michigan, it was in Wisconsin, my family is in Minnesota… I looked at it over Thanksgiving and picked it up over Christmas break. Road salt does nasty things to aluminum so I wrapped it up best I could.
Unwrapped and in the basement
The Duc is a springer and the dog is named Desmo. How ironic?
(Yes, I named my dog Desmo. But make no mistake, I like my dogs even more than my Ducs. As for my username, I needed a screen name one night, he walked by as I was thinking, the rest is history)
While not actually round, the "roundcase" sidecovers are more curved than the later squared off "squarecase" bevels.
Yeah, the bike was a little ratty, but mostly there. I knew NOTHING about bevel Ducs when I bought it and decided that if turned out to be too far gone I could make back most of my money parting it out. At the time I wasn't sure if that was smart. In retrospect is was probably the best deal I'll ever get on a Ducati.
When I bought the bike you could get decent, running GT's for about $6000. I estimated I'd have up to $10,000 into rebuilding this one. I had thoughts of buying one of the retro styled bikes instead, but decided that a new bike would depreciate so I'd lose money there too. Plus, this one would be the real deal.
Over the three + years I spent rebuilding this, roundcase prices shot up to the point I'm sure it's worth at least as much as I have into it now. I'm pretty happy I got it when I did, I don't think I could afford to rebuild a bike like this at today's prices.
The teardown begins
I didn't have a tool to lock the engine so before I removed the chain I did this and then broke loose all the locknuts on the crank and cams. The nut holding the countershaft sprocket on was only finger tight so I didn't need it for that.
The inner workings
Belts? We don't need no stinkin' belts!
Most of the aluminum looked like this
Nice air filter!
When I bought it we thought the engine was locked up, but when I got it home I noticed the engine would turn backwards but not forwards. Hmm... The bike has sat for years, there's cat food in the air filter, I wonder what kind of crap is in the cylinders?
The front head. You can just see the dirt that built up in it that stopped the piston from going over TDC. (keep in mind this cylinder is horizontal when in place)
And the corresponding cylinder/piston
No major damage done!
She's going to need some new pistons, both of them were scuffed and the rings in this one were locked solid.
The odometer read a bit over 62,000 miles when I got it, and the speedo cable was broken so I'm not sure just how many miles were on the bike.
Apparently flaking rockers are nothing new. I didn't take any pictures of the rockers (which were losing their chrome) but the cams looked like this.
The rest of the engine looked pretty good actually so I'll spare you the pics of the rest of it until rebuild time. Which reminds me, this is a bit out of order. In real time I had gotten some work done on the chassis before I started pulling the engine apart, so enough of the engine for now and on to the rebuild.
The first order of business was replacing dull with shiny. I was enrolled in an auto restoration program when I was doing this so I had access to about every tool known to man. Every night I had class I'd load up a few more parts and slip them into the bead blast cabinet at some point during the evening. About the only part I didn't blast myself was the frame - that got done professionally, while I waited. Money well spent BTW.
I didn't even bring that home after it was blasted, I dropped it off at the powdercoater, along with some other bits. Pretty much anything you see that's black on this bike is powdercoated, except for the headlight mounts.
And now my first "Do as I say and not as I do" moment. I brought the frame directly from the blaster's to the coater's. Don't do that. Take it home, Look it over, inspect it.
I knew the frame had rust pits on the battery tray, I knew the coater did show quality work. I wasn't building a show bike. I told him to ignore the flaws on the frame.
He did. So when I got the frame home, I discovered these bright and shiny lumps of something on the frame tubes. I was heartbroken. well first I was pissed off. Then I went to build my case on why he was going to fix it for me. It would be easy. I had taken a stupid amount of digital pictures of the bike before I brought him the frame. All I had to do was show him pics of a smooth tube in the areas where the lumps were now.
Except, when I went and looked at the pics? yeah... not so smooth. I thought it was just grunge but apparently someone had done some nasty welding at one point and I was stuck with the aftermath. My fault. That's when pissed off turned to bummed.
So, Tip #1. Examine EVERYTING very closely before taking it somewhere to be refinished. Shiny flaws look much worse than grungy flaws. Trust me on this.
Tip #2 - If you haven't got a decent digital camera, BUY ONE. And use it. Take pictures of everything, from every angle. Capture it all before you touch it and while you're stripping it down. You never know when you'll come up with a question and digital storage is cheap.
Moving along, after thoughts of stripping it again, smoothing it all out, and refinishing it, I came to the realization that the worst of it would be hidden once the bodywork was installed. There was only one spot that would show and it wasn't that bad. I played a little trick to hide it and in three seasons of riding, no one has noticed, or at least mentioned it to me.
Yeah, I got lucky.
I sent the swingarm to Syd's Cycles to get new bushings installed and reamed to fit a new pivot tube.
Centerstand, swingarm, and triples in place.
Next came wheels. I was a bicycle mechanic for about ten years and have built, who knows, 100 wheels? I've probably trued thousands of them. So of course I built them myself. Flanged Excels and stainless steel spokes from Buchanan's replaced the mis-matched, rusty steel rims.
The hubs were bead blasted to remove the corrosion. I thought this was all they'd need, but when I sat them down next to the new rims and spokes it became obvious I was wrong. The hubs still had a sort of greenish tint after blasting, so I took some alloy wheel cleaner to them, hit it lightly with a steel brush, rinsed and dried them off, repeating as needed until they looked presentable. I also polished the center section of the front hub with a little Simichrome. The hubs don't quite look new now, but they do look nicer than they did after being glass beaded and infinitely better than when they were corroded! I used the same cleaning method on the backing plate and the cush drive.
Add some fork tubes from Forking by Frank, a few engine parts, and it's time for yet another mock up. (yeah, the rotor is done here too. Not all these pics will be in chronological order)
And that's enough for one night. More later.
Keep it comin' sir. :ear
Cool. Gonna be watchin' this one as I have a '74 750 GT that I'll be starting on soon.
This has the makings of a great thread..
Thanks for the encouragement. Sometimes I wonder if maybe I'm posting too much info on my little part of the world. Not everybody is as infatuated with Ducs as I am... or so I've been told. By a few different people...
Some of what I'm posting here comes from my website, so it was written years ago. Hopefully when I add updates to what I wrote then it won't get too confusing.
Back to the wheels. Add some no name shocks and a pair of Avon Roadrunners
Thems the Brakes...
The master cylinder for the front brake and the lever for the rear brake were both frozen. The rear lever was simply a matter of penetrating oil and patience. The front was more involved. I tried to force the piston out of the master cylinder with a grease gun (typically very effective in pushing brake components apart - the fitting on a grease gun uses the same thread as some brake fittings. Try it! It's more controlled than compressed air) but it wasn't budging. So I ended up drilling a hole in the piston, tapping threads into it, and forcing it out by threading a bolt into it. I cleaned up the master cylinder body, including opening up one of the holes in the bottom of it. Rebuild kits are still available for these (Try Yoyodyne or MG Cycle), I ordered one and sent the master cylinder out to be anodized.
The caliper was pulled apart, cleaned up, and sent out to be anodized too. This was probably a mistake - I didn't care about having the old style caliper and it would have been cheaper to buy a new Brembo F08! If I hadn't already bought the parts to rebuild what I had, I would have ordered a new caliper from Yoyodyne. But at the time, the only replacement calipers I knew of were expensive.
The anodizing was done as a favor by a friend of a friend. The price was right (freebie!) but it took about a year to get the parts back. The black isn't all that deep, sort of gray looking. Not complaining here, just pointing it out to anyone who might be expecting more. I was warned it might not turn out that great before they were done but I had nothing to lose. Three years later I don't notice the color of the caliper. And the master cylinder? I could never get it to stop leaking so I ended up replacing it with a new one. (With a rectangular reservoir)
The rotor was in pretty poor shape from years of sitting. Rather than try to recondition it, I bought a new one from Road and Race in Australia and painted the center of it to keep it from rusting.
The caliper looks alright in that shot? It looked grayer in real life.
The rear brake was in decent shape, other then the lever, so the only work I needed to do was to clean everything up.
I got a braided front brake line from Steve at Bevel Heaven that has a stock-looking black outer covering but does away with the small steel line used on the stock set-up. It was too long so I sent it to Galfer and they shortened it up for me for a very reasonable price. Steve has since modified his specs for the lines so they should fit better than mine did. I should also point out I used lower bars than stock, so I was expecting the line to be a little long.
While I'm thinking about it - I replated a lot of the hardware at home using a kit from Eastwood. It doesn't look anything like chrome but then it's not supposed to. Process was to bead blast the bolts, plate them for a few minutes, then burnish them with a stainless brush. Here's a shot of the progression from rusty to blasted to plated to burnished. Note the threads should have been cleaner on the centerstand bolts (right side), Oops...
I was very happy with this for the first season, then the bike got caught in the monsoon known as the Indy MotoGP 2008. The day after I got the bikes home I went into my garage and found a bunch of rust on the 750. Arg... not as weatherproof as I was led to believe, but maybe I just didn't leave them in the solution long enough. Or maybe they're just doing what Italian bolts do, I dunno.
Lovin' the build up. I see your posts on the bevelhead list form time to time. I guess we don't have to wish you luck since we know how it all turned out.
This is an excellent thread!!
Buildup/restoration threads are a bit like ride reports; it's not only about the bike, but also about the quality of the story and presentation.
Thanks for sharing, and please go on.
Good stuff, keep it coming.:thumb
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