My 750 S is now a 900 S

[ir_joep]

Hi there,

Last week I was able to finish the engine swap on the 750. I had bought a 900 ss engine from 1990. Because the sport I have is from the last production batch, it already hade the proper frame dimensions for the swap.

It was certainly a learnig curve on the interchangability of ducati parts....

The 900 engine now runs on a the 750 kokusan ingition so I did not need to change any wiring.

Due to the bad weather, I have not put many km on the clock but the few I did were perfect.

Thanks,

Joep

[ducinthebay]

Damn Joep,
you beat me to it. I am planning the same upgrade this winter. What carbs did you end up with on that? Alternator leads are the same I guess, and I'm assuming you had Kukosan ignition on your 750 motor? Where did you put the oil cooler? Or should I ask how you adapted the lines off the engine?

I would assume that you also simply used a 900 SS swingarm so that the pivots match.

Love to hear about your impressions. I'm toying with doing a minor top end on the motor before I install it with some hi comp. pistons.

Cheers,

[ir_joep]

Hi Ducinthebay,

To answer your questions.

The 900 supersport of 1990 comes with a weber carburetor. So I had that one on. I just love the weber for the sound they make and take the 4000 rpm lag for granted. (it is only when you open the throttle full). Going this route no alteration had to be made.


Yes, I used the kukosan of the 750. (they have the same advance curve as the 900 ingnition) Inside the 900 engine the brackets for the kokusan were already cast and threads were made. It was just a bolt on conversion. I also used the 750 alternator, rotor and flywheel. With the flywheel I was running into trouble because it was touching the side cover of the engine. I had to take some material of the engine sidecover to "free" the flywheel. For the future I'm planning an other flywheel or take some material of with the lathe. The alternator exit for the leads is on a other position (front) on the 900 so you might need to extend the leads.


About the oil cooler: Again the 900 s of 1990 has simular set up. It just bolted on. No alterations needed. My guess is that a later type will bolt on also???


And yes I did use a post 1990 900 ss swing arm --> again a bolt on conversion, but to be shure also buy/get the pivot axel and shimms also. Bolt on exept for the brake retainer pin. I had to cut some material off because it stopped the (16") wheel from turning I 'm scanning the internet for a 1990 900ss swing arm because the have a simular look as the 750s 's swingarm. I did not look into the hugger. At the moment I have none.

The 750 s exhaust will not fit. I did buy a set of a post 90 900 ss. Fits like a glove.

I did not know the state of the 900 engine when I bought it. It was a gamble. So my priority was to get it running with the lowest possible investments. If the engine turns out ok I will upgrade an improve.


Good luck and all the best with you conversion. If you need more info/help just ask.

Cheers Joep

[ir_joep]

and you will need 1 long bolt to replace the 2 top engine bolts of the 750 because of the differance in casting between the two.

Cheers Joep

[higgy]

The 900 supersport of 1990 comes with a weber carburetor. So I had that one on. I just love the weber for the sound they make and take the 4000 rpm lag for granted. (it is only when you open the throttle full). Going this route no alteration had to be made.

No flat spots,no sags and linear throttle response..........http://mysite.verizon.net/vze2hw9t/

[Mc tool]

reading with much inerest.
Yesterday I recieved a totally unsolisitored ph call ( Di answered the phone so it was even better ) from my good friend ( especailly now ) Rodney from the local yamaha shop, advising me that they had just traded a 1989 750 sport , anyhow Dianne was still pissing blood while I was 1/2 way into town to check it out, ( I think she has put a hit out on Rodders )....... faarrrrk its rough . Swing arm is well shot.
Apart from the wheels ,frame and fairing I have most of a 97 900ss. Will the 900 ss swing arm fit the 750 s motor ?Would help to know b4 making an offer. Thanks
Hamish

[ducinthebay]

No, the newer swingarm will not fit the Sport motor. The pivot is basically the problem. The Sport pivot is larger diameter, and the cases are narrower. If you have the newer motor, such as the 750 or 900 motor, then you can drop any of the newer swingarms.
I have two Sports, both with newer swingarms. One we made inserts for the motor that housed the newer needle bearings and spaced the cases out like the newer motor. Lots of problems in doing this. The other, the previous owner took a 750 steel ss swingarm and cut the forward arms, bored them to fit the old pivot pin, and re-welded them inboard to match the old cases, and added some bracing. This is the easier method as the cut, bore, and reweld are fairly straight forward.

However, if you plan on dropping a newer motor in that Sport frame, just get the newer swingarm, and Bob's yer uncle.

Cheers,

[Mc tool]

Thanks for that.I've put in a stupidly low offer , so we'll see what happens. Its obviously been owned by some penis fingered retard,and as it aint worth putting back to original anything could happen mmmmmmmmmm I wonder if them upside down forks etc will fit ?

[ducinthebay]

With your offer, explain that the broken swingarm is no longer available, and even if you do find an old one from a Sport of F1, it will cost you another $600 or so. The original swingarm was prone to cracking anyway.

Good luck with that offer, and that project.

[Mc tool]

I passed it up . There was just to much wrong, and I could easilly see that I would be better off just buying a tidy one if I really wanted one . Thanks for your input tho
Hamish