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Discussion Starter · #1 ·
I have just bought a 1990 900SS and are selling my 97. I know many think I am changing to the inferior model, but I love the looks and actually sit better on the 1990. I know much can and have been done to these so I would like to know which modifications You recommend to improve the bike. Engine, electrics, forks, wheels the works.
The bike is supposed to already have the 851 clutch, hi comps and 40 Dellortos fitted
I have some parts left over from the 97 that were never fitted like a Andreani Misano cartridge kit a Nitron R3 rear shock (will try to rebuild this to the correct length) and FCR 41s as well as a couple of later 900 engines.
Should I look for some later 41mm USD forks and fit the cartridge kit or sell these and look for something else. Should I look for crowns with different offset from the original?
I know the wheels are the same as the Paso, are these woth saving or shouldI look for something else?
I also have two later 900 swingarm, one square from a carby and a ie /ds swingarm. Are any of these worth fitting?
 

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the engine has the narrow alt and crank is shorter on the left, and it has the early style clutch slave in the cover. a later engine will have the more reliable clutch slave on the left. apart from that, same as 91-97 engine really.

steering head bearings are smaller, but you can get a 32005/26 which will allow the later 91> ss triples to fit and then you can fit usd forks from later models. the std 40mm m1bb have teflon bushes, so you could adapt inserts into them if you wanted to stay with the original look. just keep in mind that having adjustment doesn't mean you have good suspension. lots of gsxr forks will go into later ss triples too.

shock will be much the same, as is swingarm. check it for cracks.

wheels are 17 from 851/900ss with 17mm axles, so heavy but otherwise ok.

battery box in front of carbs can hamper some carb fitments, but work around as required.

piss off the digiplex ignition and fit something else is a good idea. ignitech will go straight in, or can fit kokusan stuff as well.
 

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Discussion Starter · #3 ·
Haha, I think we might have talked on FB as well ;) If so I must say thank You for all the help Your info has given a Ducati novice when it came to modify the '97 and finding cams for the Pantah project as well!
 

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Discussion Starter · #4 ·
Belter ; Do You know if the same bearings can be used for the ST4 triple tress/fork crown in the older frame?
 

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Not Belter but the ST series use a larger caged ball so I doubt they would work as the stem is likely larger than a 900ss stem.
 

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i thought there was an all balls bearing that will work - needs to be 35 x 52. but looking now it seems to not exist.
 

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Discussion Starter · #7 ·
Turned out that they were quite different. The length is not that far off but the diameter is quite different. Old stem is 25mm while ST4 is 33ish mm. ST4 is caged ball while the original is conical bearings. New stem might be the easiest way..
980890
 

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what's the st4 offset? the st4 lower triple is the same as the 91 - 07 ss/ssie (30mm offset) or m400/600/750/900 03 - 01 (25mm offset) lower triple apart from the stem size, so why not use the one that fits straight in?

did i get the offsets the right way around? eric?
 

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Discussion Starter · #9 ·
I am not sure about the offset, but I think 30mm. I have some legs from a ZX10r that I want to use and they are 50/54 so cannot use 91-97. But 98- might fit? And if stem size is the same as pre 97 there should be bearings to make it work
 

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all non sbk showa and marzocchi 91 - 10 ish are 50/54.

i think 90 uses the 25 x 47 bearings like a paso? 91> are 26 x 52. check the 90 bearing od.
 

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You can probably get the right bearings at an industrial supply store or bearing house. All Balls carries only a few of the possibilities.
 

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Discussion Starter · #13 ·
No, Belter was correct. This combo is a no go unless You make a new stem. I have gotten hold of a SS triple tree that is also 50/54 and will fit w the correct bearings. That is at least the case w the biggest supplier in Norway.
 

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Nichols engine mounting bolts, worth the price...

Fred
 

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Discussion Starter · #15 ·
steering head bearings are smaller, but you can get a 32005/26 which will allow the later 91> ss triples to fit and then you can fit usd forks from later models.

shock will be much the same, as is swingarm. check it for cracks.

battery box in front of carbs can hamper some carb fitments, but work around as required.

piss off the digiplex ignition and fit something else is a good idea. ignitech will go straight in, or can fit kokusan stuff as well.
Turns out You wre spot on ;)
Swing arm cracked, and trying to fit FCRs now the battery box is in the way

I have fitted the 32005/26 bearings but these seems to be lower in height than the old ones. Top is no problem, but the lower triple trees hit the frame. So what is the best option; make a spacer underneath the bearing in the frame or space up the bearing on the tree? Or a bit of both?

Did You have the same problem when You did the swap?
 

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not a swap i've ever done, but i'd probably go under the bearing on the tree. make it a large one that seals the bearing from crap thrown up.
 

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Discussion Starter · #17 ·
Well I ended up using three different spacers. One on the stem, same size as on the 90 stem. And then I took out both the std spacers below the bearing races and made some new ones that were taller. So now everything fits, but I need to play around to make the steering stop work as "normal" Also fitted the front wheel (meant for a ZX10r) after I modified the spacers
 

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