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 Post subject: 17" conversion
PostPosted: Fri Aug 29, 2008 4:22 am 
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Joined: Fri Aug 15, 2008 4:10 pm
Posts: 84
Location: Escondido, CA
model: 750 Sport
year: 1990
Hello All,

I have picked up a set of 900 ss front and rear rims and rotors. I am in the process of trying to get a hold of 50 mm front forks from a 900 ss as well.

Does anyone know if the steering head on the 750 sport is compatible with the 900 ss upper and lower triple clamps.

Also is there anything else I should be aware of with using 900 ss parts for a 17" conversion?

Thanks

Joe

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1990 Ducati 750 Sport (mine)
2007 Piaggio BV 500 (mine - daily driver)
2008 Piaggio MP3 500 (wife's)

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 Post subject: Re: 17" conversion
PostPosted: Fri Aug 29, 2008 9:34 pm 
hello joe. i have done this and it is very worth it! first we will start with what you will need. for the front end you will need a complete front end from a 900ss. use the first gen model 91 to 98 or 99. consisting of forks( adjustable prefered but the nonadj showa is ok too) top and bottom clamp, brake calipers and hoses, fender, wheel with axle and speedo drive and clipons(stk 900 or whatever you like). for the rear end you will need 4.5 in wheel from a cr with sprocket carrier, rear brake caliper,hose and carrier(i think a sp setup will work if you can find one). i installed a 39t rear sprocket on mine to get the gearing close to stock but you can use whatever you like. now there are 3 steps to this conversion. 1, front end 2, rear end 3, chassie adjustments. ok, this is not as hard as you would think. first the front end. the trick to this is the lower fork clamp. find a good machine shop and have them press the steering stem out of the stock lower clamp and install it into the 900ss lower clamp (the stem has to come out of the 900 clamp first) now this is important, they have to press it in straight! next is the steering head bearings. this is a good time to install new bearings , the old ones are probably bad anyway. be careful, there is a aluminum spacer under the lower brg that can be damaged if you hack. the important surface on this part is the outer edge. this is where the seal that is in the steering head rests. installing the lower bearing is just like stock. the top bearing has the same setup but that just slips on, the brg races install just like stock. install the fork clamp like stock and adjust. you might have to use a washer to space the top clamp but this is no big deal. now install the fork,wheel, calipers, and fender like stock, thats it. the rear wheel is much simpler. the trick for this is the sprocket carrier. the cr wheel uses the same diameter axle as the sport so bolting everything up is a snap but the chain does not line up because the 900ss carrier is too close to the swing arm. what you have to do is have that good machinist you found turn down the mating surface on the carrier where the sprocket seats. you also have to cut down the sprocket mounting studs the same amount. now i did my conversion a few years ago and i cant find my notes so i dont remember how much to remove but it isnt very much and all i did was bolt everything up and measure it. so if you know what your doing ,you should have no trouble handling that. connect the 900ss calipers to the stock master cylinders front and rear. install the chain and the installation is done. i dont know if other models parts will work so be careful. if you cant get a complete front end assy, make sure all the parts fit together. example, there are two different front dia axles out there, i think it is early and late models, not sure. now for the chassie. 1, the only cush drive the sport has is the one in the rear wheel. it pretty big so it worked ok but the 900 has two cush drives, one in the clutch assy and a small one in the rear wheel. this small one is all you will have so the drive line will feel very direct, kind of like a race bike. this can feel rough and may be a little hard on your chain but these bikes are hard on there chains anyway and mine lasted about 12000 miles. 2 the side stand will be too short so take it to a welder and have him install a thicker foot (about 3/4 in) or whatever you want. 3 the front fairing sits lower then the 900 so the front fender will hit the underside of the top piece under hard braking. what i did was move the entire fairing assy up as much as possible by elongating the mounting holes in the main fairing frame. then i installed a racetek valving kit with heavier springs, and finally elongated the mounting holes on the fender and moved it closer to the tire. it still hits sometimes when im on the brakes hard but its ok. a carbon sp fender sits lower so that might work. 4 the speedo cable is too long so it does not last as long but a shorter cable might be out there from another model. im looking. i think that is all but i might have missed something so if you have a question, ask me. good luck blaster


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 Post subject: Re: 17" conversion
PostPosted: Fri Aug 29, 2008 9:49 pm 
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Joined: Fri Aug 15, 2008 4:10 pm
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Location: Escondido, CA
model: 750 Sport
year: 1990
Blaster, You are awesome! Thanks so much for a great description of what to do. I have read bits and pieces here and there, but yours is the best.

Thanks, I will post pictures when I am done.

Thanks

Joe

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1990 Ducati 750 Sport (mine)
2007 Piaggio BV 500 (mine - daily driver)
2008 Piaggio MP3 500 (wife's)

My Ducati Blog site
http://projectducati.blogspot.com/

Stupidity is not a crime, your are free to go ;-)


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 Post subject: Re: 17" conversion
PostPosted: Wed Sep 17, 2008 4:55 pm 
This deserves to be in a 750 Sport FAQ somewhere!!

Excellent!


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 Post subject: Re: 17" conversion
PostPosted: Wed Sep 24, 2008 4:17 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5237
Location: southern Germany
model: 750 Paso
year: 1987
you`re right. Unluckily I can`t create one so I added the link to the P750 Faq for the moment.

G.


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 Post subject: Re: 17" conversion
PostPosted: Sat Sep 27, 2008 1:05 am 
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Location: Hudson Valley, NY
model: 750 Paso
year: 1988
You asked for it, you got it!

Now it's up to you guys to populate it.

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'88 750 Paso * '87 750F1
'04 Multi 1080s * '88 650 Indy
'65 250 Monza - Moto Giro Project

Click HERE--> 750 Paso Tech FAQ
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 Post subject: Re: 17" conversion
PostPosted: Sun Nov 02, 2008 6:38 am 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
The 17's on the Sport is the change that will make it one of your favorite bikes. Well worth the effort.

An easier way to fix the chainline is to use a sprocket carrier from a 750 which had the 4.5" wheel. There are two sprocket carriers for the 17mm axle wheels, both have different offsets. The one for the 750 has the chain farther inboard, towards the center (farther away from the swingarm) The one from the 900 is spaced further outboard. The two parts start as the same casting, but one is just turned down more in manufacturing, so they are interchangable. The 750 motor is a 5 speed, and the 900 is a 6 speed, so the countershaft sprocket moved out just a bit for the extra gear.

I used a laser alignment tool to confirm the chain line. I also used a standard countershaft sprocket and retainer plate, not the special one for the Sport or Paso countershaft sprocket. If you have one of those special countershaft sprockets, you can run a 5." rim and a 180 tire, and use the 900 sprocket carrier.

Always confirm your chainline when making a conversion like this. A misaligned chain will wear quickly, and sometimes fail catastrophically. It will also beat up your output shaft bearing, which is a real pain in the ass to fix.

I used a 5.5" rear wheel on mine, but also went with a 170 rear tire. The narrower rear tire helps turn in and clears the chain.

Oh, and the last important note. All of this is assuming you have a later model 750 Sport that has the 3mm spacers on the RIGHT side of the motor between the frame. This was done to fix the chainline, and also so they could drop in the new 900 motor a year later. Almost all US versions had the 3mm spacers. Earlier versions without the spacer had some really deep dished countershaft sprockets which are very difficult to find.

Other than that, I agree with the previous post. Swap out the entire front end as there is nothing there worth saving. The back is as easy as pulling the axle out and swapping the parts. Another option is to get a front end from a 907 Paso or first year 851, both had the M1R fork, 17" wheels, 320mm brakes and 4 piston calipers.

If you have gone that far, you may as well get a new shock for the back too. Get an aftermarket shock that allows you to adjust the length. Anything that fits the SS series will fit the Sport. The cheapest/fastest route is to get a shock from a 900, which is a 1/4" longer than the 750 shock, and will help speed up the steering, which the Sport certainly needs.

What you have in the end is a really lovely handling bike. Its much better behaved that anything from the SS series.

Cheers,

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Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.


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 Post subject: Re: 17" conversion / sidestand fix
PostPosted: Sun Nov 02, 2008 7:05 am 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
Oh, one more thing.
A quick an easy kickstand modification is to use a bumper/brake from a roller skate, also known as toe stops. You can buy them in different hardnesses, and they are only $6 -$15 for a pair. They take 5/16" bolt in the middle. (6mm will do just fine) Just drill and tap the bottom of the foot of your sidestand and bolt on the bumper to the foot of your kickstand.
http://www.skates.com/category-s/244489.htm


It has a few advantages.
1. I has a nice soft foot which conforms to the ground
2. Of course the added height so the bike sits right.
3. A nice wide foot which is good in sand or soft soil.
4. If you forget to put up your stand, the soft rubber foot will give way easily and won't spit you on your ass for forgetting something basic, like your sidestand.
5. No one else on you block will have one.

I stole one off of my wife's skates that she hasn't used in 15 years. I did mine 3 years ago and have had no negative side effects. Makes you wonder why all bikes don't have them.

Cheers.

_________________
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.


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 Post subject: Re: 17" conversion
PostPosted: Mon Nov 03, 2008 6:31 pm 
you are 100% correct about how this conversion transforms the sport from a bike who's handling is ok when the tires are fresh, the suspension is in good shape (the marzocchi pbs1r shock is not the best), and the gods are pleased. into a wonderfully responsive, stable, capable, fun bike. mine handled better then my 900ss and i even like it more then my 916 though at over 100mph the 916 does come into it's own. one thing though, the 750ss is pretty rare in the usa and finding a carrier for one could be a problem. on the other hand, 900ss stuff is still common and a carrier from one of those is easy to find. i cound'nt find 750ss stuff very often so i had to make due with what i could find. the curse of conversions. blaster


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 Post subject: Re: 17" conversion
PostPosted: Mon Jan 19, 2009 4:27 pm 
I am getting closer to the idea of a conversion... It looks like also the Metzeler M1 compK in 160/70 (which was my favourite option before the conversion) is a "dead end street" since the actual catalogue of Metzeler does not show this dimension.

What I am now interested in:
blaster wrote:
... for the rear end you will need 4.5 in wheel from a cr with sprocket carrier, rear brake caliper,hose and carrier(i think a sp setup will work if you can find one).


Could yomeone explain to me please, what means "CR"???
Thanks for the moment, there will be more question once I am deeper into it....

Cheers
Felix


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 Post subject: Re: 17" conversion
PostPosted: Mon Jan 19, 2009 5:33 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5237
Location: southern Germany
model: 750 Paso
year: 1987
CR was the café racer version of the SS. It didn`t have the full fairing and it actually was a cheaper version of the SS. As far as I know it came with a steel swingarm and a 160 rear tire on a 4,5" rim, while other Supersports had a 5,5" rear rim.
I think the name CR was only used in the US and some other countries while in Europe it was normally called "nuda" (naked)

G.
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 Post subject: Re: 17" conversion
PostPosted: Mon Jan 19, 2009 8:17 pm 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
You can also find wheels from the Monster series, as long as they use the 17mm axle. As it was with the SS series, the 900 used a 5.5" wheel, and the 750 used a 4.5" wheel.

The two different wheels have different offset of the sprocket carriers. The 5.5 has a chainline more outboard than the 4.5 wheel. (this was mostly because of the 6 speed tranny, and 5 speed tranny)

With any wheel modification like this, check your chainline. There are some dandy little laser devices now that work really well. Here's the one that I use. http://www.profiproducts.com/profilasercat.html


Cheers,

_________________
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.


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 Post subject: Re: 17" conversion
PostPosted: Tue Jan 20, 2009 9:08 am 
Does that mean, that I defineteley have to use a 4.5" wide rim for the rear?
@Joe, how far have you come in the meantime?

Thanks
Felix


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 Post subject: Re: 17" conversion
PostPosted: Tue Jan 20, 2009 11:04 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5237
Location: southern Germany
model: 750 Paso
year: 1987
according to this a 5,5" will fit as well http://www.ducati-club-cavallo.de/technik/750s.htm
A 4,5" will probably give less clearance problems.

G.


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 Post subject: Re: 17" conversion
PostPosted: Tue Jan 20, 2009 2:14 pm 
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paso grand pooh-bah
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Joined: Sat Sep 03, 2005 12:00 am
Posts: 1318
Location: SF Bay Area
model: 750 Sport
year: 1990
I am running a 5.5 rim and a 170 tire without problems on a 1990 Sport that has the 3mm engine spacers on the right side.
The original Sport had a 160 tire, and doesn't really benefit from the wider tire in the back. I only did it because that's the only width that the white wheels come in. I had a set of silver 4.5 wheels on it before that, and the clearance to the chain was a lot bigger. The chain runs pretty close to the tire now, but that is true on even stock bikes. Certain tires actually touch the chain on my ST.

Just remember that bigger tires will slow the handling down. The sport already has a pretty relaxed geometry, which makes it stable at speed, and slow to change direction on tight twisty stuff. If all you do is trackdays, then put on the big meat.

Cheers,

_________________
Duc in the Bay
1990 750 Sport x2-Rosso Blanko (900ss copy) & Nuovo Nudo (Scrambler project)
1991 907 -mostly stock
2002 ST4s - Lots of mods.


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