Rear shock info

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
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jr60
Posts: 10
Joined: Thu Jun 02, 2011 9:02 am
model: 750 Sport
year: 1989
Location: N Ireland

Rear shock info

Post by jr60 »

While the rear shock on the bike is in pretty good condition (bike had only 8k miles), I still want to re-oil/gas it - anybody now if a manual is avail for these shocks (workshop manual doesn't even mention it!) or volumes/weights needed? It came with 32mm preload (top of spring to end of threads) is this the factory setting?

Cheers

Johnny
'04 ST3
'92 888 Fogarty Corse Rep
'89 750 Sport
M900 Cafe Racer Project
900SS TT1 Project
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Mustang505
Posts: 134
Joined: Wed Jan 28, 2009 9:27 pm
model: 750 Sport
year: 1988
Location: Auckland, New Zealand

Re: Rear shock info

Post by Mustang505 »

Johnny
There is a manual on this site for the Marzocchi with the external resorvoir - which i think is fitted to the paso. Very similar to the sport Marzocchi. I followed this to rebuild mine, just make sure you put all the washers back exactly the same as you took them off. Initially i refilled with 15w oil but it did not work. changed to 5w and it now works great. I set the preload to suit my weight to allow for 10mm of sag. Set rebound to 15 clicks in or till you get a nice rebound feel when pushing down at the rear of the bike. Otherwise there is not much to it.
Cheers
Clive
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jr60
Posts: 10
Joined: Thu Jun 02, 2011 9:02 am
model: 750 Sport
year: 1989
Location: N Ireland

Re: Rear shock info

Post by jr60 »

Thanks for the info Clive, don't think its needs a full rebuild as the seals seem OK, just a re-oil/gas. Will prob leave it with my Ohlins guy as it should be filled with Nitrogen anyway. Will let you all know, if I gleam any info from him re the shock.

Johnny
'04 ST3
'92 888 Fogarty Corse Rep
'89 750 Sport
M900 Cafe Racer Project
900SS TT1 Project
User avatar
Mustang505
Posts: 134
Joined: Wed Jan 28, 2009 9:27 pm
model: 750 Sport
year: 1988
Location: Auckland, New Zealand

Re: Rear shock info

Post by Mustang505 »

yep i put 78% nitrogen in mine.
Cheers
Clive
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Mustang505
Posts: 134
Joined: Wed Jan 28, 2009 9:27 pm
model: 750 Sport
year: 1988
Location: Auckland, New Zealand

Re: Rear shock info

Post by Mustang505 »

Hi Guys
anyone have a Sachs rear shock off a '90s 750ss fitted to their sport?
I bought one off e-bay a while ago with an idea of using it some time. Showed it to a top shock guy here in NZ who said with an Ohlins piston & valve fitted it will be 10 times better than the standard Mazorcchi as fitted - plus it has all the adjustments, bigger gas resorvoir etc.
I have fitted it and it clearences etc are good. Probelm is it's 8mm shorter in length. Which means the rear ride height will be 8mm lower. I don't want slower steering. Guess you could lower the front through the triple clamps by 8mm to try get back to original geomertry?

Image
Cheers
Clive
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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: Rear shock info

Post by ducinthebay »

As you have found out, the 750ss shock is just a bit shorter, but the 900ss shock is the same length as the Sport's. I can't explain why Ducati engineering did this but I can speculate/rant for a page or two. So, if you are shopping for a new shock, you should look for a 900ss shock. Lots of them about, and relatively cheap. Plenty of shops will know how to work on them. The reservoir will bump into your breather box if you still have it on your bike.

Anyway, Yes, that shorter shock will fit, and yes, it will slow down your steering, which the bike doesn't really need, and if you have the 16's on there still it will be really slow steering. Narrower tires will help speed up the steering a bit. It may be worth mounting it up there just to see what the damping and spring rate is like.

If you buy an aftermarket shock, many of them are adjustable for length, which is nice.
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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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: Rear shock info

Post by ducinthebay »

In doing a bit of research, I found that the post '02 shock is another 1/4" longer.

As best I can conclude right now.
750ss = 12.75"
900ss = 13.0" (same as 750 Sport)
'02 later = 13.25"

Always ask the eye to eye measurement before you buy.

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.
User avatar
Mustang505
Posts: 134
Joined: Wed Jan 28, 2009 9:27 pm
model: 750 Sport
year: 1988
Location: Auckland, New Zealand

Re: Rear shock info

Post by Mustang505 »

thanks for the info DITB, so best bet would be go looking for a +'02 900 rear shock. the few i have seen are Showa as appoased to the Sachs i have? My shock expert did say you can fit an Ohlins body to my Sachs shock to give it the extra length as well = $120.00 on top of the valve + piston upgrade.
Cheers
Clive
SimonT-Dk
Posts: 15
Joined: Wed Jan 05, 2011 7:48 am
model: 900 SS
year: 1990
Location: Copenhagen, Denmark

Re: Rear shock info

Post by SimonT-Dk »

Would this fit a 1990 900ss, like mine :)

http://www.ebay.co.uk/itm/DUCATI-900SS- ... 2a1505adcf

-Cheers

simon
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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: Rear shock info

Post by ducinthebay »

Ah, the loophole of common knowledge. The 1990 900ss. Not quite sure what they put on that bike as far as a shock. Magazine articles said it was same as the 750 Sport, just better sprung.

The swingarm is unique to that year only.
However, the 750 Sport and 91-98 900ss had the same length of shock, same bolt sizes holding it on, and the same width space on the frame and swingarm to attach the shock. So everything before and after your bike fit, same same.

So I would say that there is a 95% chance that it will fit right in, straight away.
The shock reservoir may bump into your crankcase vent box, if it is still on your bike.

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.
SimonT-Dk
Posts: 15
Joined: Wed Jan 05, 2011 7:48 am
model: 900 SS
year: 1990
Location: Copenhagen, Denmark

Re: Rear shock info

Post by SimonT-Dk »

Well The box is not on the bike for long !! :D
I Will nye The shock and hope it Will on my bike :thumbup:
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ducinthebay
paso grand pooh-bah
Posts: 1323
Joined: Sat Sep 03, 2005 12:00 am
model: 750 Sport
year: 1990
Location: SF Bay Area

Re: Rear shock info

Post by ducinthebay »

While I am always in favor of keeping the breather box, as it serves a crucial function for proper engine performance, I had to get rid of mine also, although I do have a perfectly good one on the shelf. It seems that aftermarket shocks, and the newer shocks, are larger in diameter than the old skinny Marzocchi unit. The after market shocks rub on the breather box. Haven't found a good alternative yet. I'm thinking of making a fiberglass breather box that will fit around the shock.

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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