New Member - complete rebuild of my '88 sport

[Mustang505]

Hi All
bought a '88 model sport last year and have searched world wide for info and this site is about the best there is. Mine is the ugly blue, red & white. It ran so badly when i picked it up and in a subsequent 1st attemp to take it for a ride that when i managed to push it home I was so pissed off I just pulled the whole thing apart.
Always wanted a Ducati and this was the cheapest i could find and in some ways i regret it as it does not turn me on too much and even Ian Falloon described it as "not Ducati's best effort".
But i have it - so rebuild it is! Currently it's completely in bits and I'm about to start the rebuild process. I'm will be changing:

Swing arm to an ali 900ss one - mine was a shitty steel effort
Carbs to a set of monster 900 mikunis
Bridgestone tyres 16" but 70 profile
F1 replica faring and seat
and a set of pipes to match.

Seems as most sport owners have done all the above mods so any tips from members would be much appreciated.
Also as I been through the "pull it apart" process I've learnt a fair bit about this beast so could be some help to anyone else especially getting the job done without "Ducati special tools".
thanks

[Tamburinifan]

Welcome aboard!

Swing arm to an ali 900ss one - mine was a shitty steel effort
Bridgestone tyres 16" but 70 profile

So why not 17" wheels & a Showa fork while you´re at it?

And red is not bad although I prefer Dark Blue/Silver.

[Mustang505]

So why not 17" wheels & a Showa fork while you´re at it?

Problem is how much money you have to spend or want to spend on this model. Agree 17"s and modern USD forks would be great but you also need to add to that bigger tripple clamps and a nice set of modern discs and brake calipers and the list goes on.

And red is not bad although I prefer Dark Blue/Silver.[/quote]
A German friend here has a black/silver one '89 i think looks way nicer than the red/blue/white.

[ducinthebay]

Welcome Clive.

The swingarm swap it quite a bit of work. If your current swingarm functions well, you would do much better at making it look nice, and spend the time on the front end. The swingarm pivot pin on the Sport is a larger diameter than the SS or Monster series, and the cases are narrower than the SS/Monster series. My bike has been adapted to a 900ss swingarm, but its not an easy project. You will need a good machinist, and chance are, you will need to put your engine in a mill to straighten out the swingarm bushing bores. My bike has some very custom made adapters made from stainless steel that press into the cases and have the stock 900ss needle bearings and seals. Its not a project for the faint hearted or shade tree mechanic. The bores in my cases were not aligned to eachother. This doesn't matter so much when you have bushings, as you simply ream them into alignment. But you can't do that with bearings. We spent a lot of time to get the bearing adapters from both sides to be in alignment. Again, if you have a swingarm that works, go with it and spend your money and time on a good shock or front end.

17" wheels is a much more worthwhile endeavor, but I think you need to get it running right first to truly tell what you want to do with the bike. The 17" in the rear is easy on a Sport, just get new parts and put them on.

good to have you onboard.

Cheers,

[paso750]

blue, red & white

that may not be the nicest colour combination, but on the other side not many Sports had it.
Some time ago I met a guy who had looked for one quite a long time before finding it.

G.

[ducinthebay]

Clive,
If you have a steel swingarm, then someone has already done a switch. The Sport came with an aluminum swingarm, but it was prone to cracking. can you post a picture? Maybe its the same mod as Jetboy's bike.

Cheers,

[Manxman]

Wellcome onboard, Mustang!!

Carbs to a set of monster 900 mikunis

Thats another detail which need more work than you might think. The Mikunis won´t fit in the frame without bigger works. Means cutting and welding of frame parts is necessary, there is a piece of the frame near steering head which need another place, I think also the battery plate is different in later SS models.

The Weber carbs are not so bad as all people think, and remember they have a 44mm bore diameter, thats more than all Mikunis or Keihins!! I have thrown away they crappy fuel pump out of the tank and installed an external membrane fuel pump from a Yamaha (driven by vacuum from the intake line behind the carb). Since then, the bike has changed its character!!

Cheers
Felix

[blaster]

hi, good to have you join us. i think the biggest reason falloon said that is because of the wheels and suspension. i bought my sport new in 1990 and put 90k on it until i converted it to 17's,usd fork,and fox shock. now i rode this bike in the canyons of so cal for three years with the stock wheels and suspension and came to grips with its unusual handling traits. yes you can go pretty fast on it when everything was set right , fresh tyres,fresh fork oil, stock rear shock not too old(junk),make sacrifices to the gods, and adapt your riding style to it. i had gotten used to the old girl. in 2004,and everyone on this site will agree with me, i got sick and tired of the tyre supply problem. i had tried an avon rear once but that just made it handle even more strange. so i decided to take the plunge. it transformed the bike from a weird alice to a great feeling one. WHAT A DIFFERENCE! and you have a choise of any brand of tyres too. how cool is that. when i had the 16"s that was just a dream. i will never get rid of this bike, it's family. oh, sorry, i got carried away. one more thing. i converted to the ss mikunis in 1994 and i didn't have to cut anything. there are some things to watch out for. blaster

[paso750]

i had tried an avon rear once but that just made it handle even more strange.

Just guessimg it was a 150/80-16.

[blaster]

hi, no, it was a 160/80zr16 azaroII av36

[Mustang505]

Thats another detail which need more work than you might think. The Mikunis won´t fit in the frame without bigger works. Means cutting and welding of frame parts is necessary, there is a piece of the frame near steering head which need another place, I think also the battery plate is different in later SS models.

The Weber carbs are not so bad as all people think, and remember they have a 44mm bore diameter, thats more than all Mikunis or Keihins!! I have thrown away they crappy fuel pump out of the tank and installed an external membrane fuel pump from a Yamaha (driven by vacuum from the intake line behind the carb). Since then, the bike has changed its character!!

Felix
I've done a huge amount of measuring off a 900 monster frame vs the sport and I definitely won't be cutting any frame parts to fit the Mikunis. In fact with a set of K&Ns it all fits nicely????
Also where are you measuring the weber to get 44mm?? It's a twin choke 36mm weber. I have a friend here who is a bit of a weber fan (rebuilds mini coopers) and I tried to sell him this weber and he said it is the nastiest weber carb he had ever seen.

[Mustang505]

Pictures of some parts



Someone else said on this site that the best thing about the sport is that it's about as close as we will get to a F1 frame. Here it is sandblasted, repowdercoated and ready!





new 900ss swing arm and old steel swing arm - weight difference 2kg vs 7kg! And that's unsprung weight. This bike obviously had this changed because of the cracking problem. Was this an official Ducati mod does anyone know?




Old front Michelin new BT014.




The old girl before she was stripped down.

[ducinthebay]

The two swingarms you show are both from the SS series. The steel one is from the 750, and the aluminum one is from the 900.

I looked closely at the photos you posted of the two swingarms. I think I know what you have. The previous owner took a stock 750 SS swingarm, and bored out the pivot pin holes and used the stock Sport pivot pin (or made a new one which is longer). Since the SS cases were wider, you probably have some spacers on either side, I would guess about 25-30 mm each?

The SS swingarm pivot was smaller (20mm?) than the Sport's (25mm?)

For you to put that 900 SS swingarm on, you will need to modify the swingarm the same way. With the aluminum though, that would not be advisable. You will end up with very thin sections around the pivot pin, and that swingarm is already prone to cracking there. This is also difficult to do unless you have a very good machinist that can bore those two holes in line with eachother.

There are two other methods to put an SS swingarm onto the Sport.
1. Machine some adapters that fit into the case, take up the difference between the swingarm, and hold the SS needle bearings and seals. Use the SS pivot pin. this is on my bike, and it is a lot of work. The biggest problem was that the existing bores in the cases did not align to eachother.
2. Take a stock 750 ss steel swingarm, cut off the leading arms, bore them for the Sport's pivot pin, and reweld them to the swingarm. Less accurate machining, but you will need a very good jig for welding, and a good welder.

The biggest problem with the set up you have is the flexing of the pivot pin between the engine and the swingarm. But it will work.


Your frame is certainly one of the older versions. The later models had a diagonal brace running up to the headset. I would recommend you add it, but you have already painted the frame. That older frame wil not allow you to put in a newer motor.

Cheers,

[Mustang505]

The ali swingarm I know comes off a 900ss - as to the steel one that was on the bike I thought was an upgrade for the sport. It is really off a 750ss? There were no spaces between the arm and engine case. The dimension across mounting points is quite different - will measure tonight. I'm lucky that I know one of the machiniest who worked for Britten on the Britten racing project here in Christchurch New Zealand and he's done similar mods before so should be OK
here is pic of the engine as it is now. Definitly a 750 but Ive no idea if it's the older or newer version.

[ducinthebay]

Well, its good you have the engine on the bench. You can test fit the swingarm and get that sorted before you assemble. And its very good that you have a good machinist friend. I think you will owe him some beer soon. I can't tell from your picture of your motor what the swingarm pivot pin looks like. Maybe the previous owner made some adapter like mine. Do you have needle bearings in the cases or are there bushings?

The steel swingarm is certainly 750 SS. I think modified a bit. I would need to see a photo of the swingarm mounted to the engine to best understand what you have. There was no upgrade for the Sport that I know. Cracked swingarms were generally just replaced. I have seen them for sale from time to time on E-bay, but they wanted a lot of money.

You will need a different wheel axle and chain adjuster plates for the aluminum swingarm. The axle is shorter and has nuts on both ends.

I can't confirm or deny the vintage of your motor. Maybe someone else can.

Cheers,