Rebuilding Fork of a 900 SS (1990)

900SS90 · Post by **900SS90** » Wed Nov 04, 2009 2:51 pm

Hello:

I’m a new member of this forum. My name is Alvaro. I’m from Spain (excuse me for my English).

I bought a 900 SS (mod. 1990) and I’m rebuilding the front fork of the bike and I can’t find the type of oil that I have to put inside. I have seen in another post that I have to start with 10 wt of 15wt and check.

I would like to know if someone has a 900SS and know the oil that I have to put. I have seen the 750 Sport workshop manual (great link) and the MotoRevue and I can’t find the oil type.

I have an other request: Someone has information about this model? Because it’s very difficult find technical specs, … about this model.

Thanks from Spain.

Tamburinifan · Post by **Tamburinifan** » Wed Nov 04, 2009 3:46 pm

http://www.motorcyclespecs.co.za/model/ ... s%2090.htm

Post by **paso750** » Wed Nov 04, 2009 4:38 pm

according to my Haynes manual it`s 10W20.

G.

ducinthebay · Post by **ducinthebay** » Wed Nov 04, 2009 9:13 pm

Fork oil weight is a matter of opinion, taste, and riding style. You have to simply try it out, and most likely change it a few times to get it right. Since you can't adjust this fork (same as 750 Sport?), then your only way to adjust the rebound and compression damping is to adjust the fork oil weight. Ideally, fork oil should be changed regularly, as it picks up water and contaminants. Its certainly cheap enough.

I would start with 15 wt. and see how it feels.
Some people use ATF (automatic Transmission Fluid) which has the same basic characteristics, but is much cheaper, or other hydraulic oil.
Motor oil is not recomended, but I've been surprised (and wrong) before.
Cheers,

Desmo_Demon · Post by **Desmo_Demon** » Thu Nov 05, 2009 1:50 am

ducinthebay wrote:Some people use ATF (automatic Transmission Fluid) which has the same basic characteristics, but is much cheaper, or other hydraulic oil.

I've used "Type F" automatic transmission fluid in my M1R forks of my Paso 750 and the Showa forks on my Harley. I haven't had any issues or concerns with using it.

900SS90 · Post by **900SS90** » Thu Nov 05, 2009 7:47 pm

Thanks for your answers.

Looking for in the bills of the repairs that the previous owner send to me, I saw that he puts 15w. I have change the oil today and I have put a 20w but I have a problem in the fork because the fork bounces too much. I have to dismount completely the fork.

I have other question. I will go to put a Dellortos PHM 40 in my bike. I have these carbs from a 900 SS of the 70's. They have rigid mounting. I have seen that Malossi has a special pipes to put this carbs in the Paso, Sport,... but I have seen in the web page and the "intel" are from rubber. Do you know if there are "intel" to put my carbs or I have to do a special intel. I have put the pipes of the 70's but the rear cylinder is implossible.

ducinthebay · Post by **ducinthebay** » Thu Nov 05, 2009 11:10 pm

If your forks are still bouncy with 20wt. then I think something has certainly gone wrong in your forks. Time to take them apart.

The 750 Sport came with M1BB forks. The 900 forks look similar, except for the different brake mounts with allow you to run the bigger brakes and 17" wheels. So, your forks are pretty rare. The damping rods from the 750 may fit, if yours are too badly damaged. Honestly, they weren't a very good fork, but if they were tuned to fit your riding style, then they are a great fork.

The fork internals for a Paso will not work, as they have compression damping in one leg, and rebound damping in the other leg.

There is a big 8mm (?) bolt in the bottom of the fork leg that allows you to take them apart. An impact driver is usually best to get this loose. They are pretty straight forward once you get them apart. Any damage will be pretty evident.

A good suspension shop is your friend. I had my forks for the ST4 rebuilt and re-valved for amazing results. I don't know how much they can do with an older fork design, but its worth a call to a shop or two and see what they can do for you. They might be able to install cartridge emulators, but now I'm speaking over my head.

If your forks are completely shot, the last option is to get forks and triple clamps from a newer SS or Monster. Some are completely adjustable, and you can fit your stock front wheel and brakes to them. Figure about $300 - 500 for a good front end. Some of those USD (upside down) forks are not adjustable, and those will be cheaper. May be better than what you have.

Cheers,

Post by **jcslocum** » Fri Nov 06, 2009 7:41 pm

There are manuals that can be downloaded here: http://www.duc.nu/manuals/

Post by **paso750** » Fri Nov 06, 2009 7:54 pm

you can find the 750/900SS >91 manual for free. It´s 187MB or so.

can you describe "bouncy" ? Does the fork feel soft, does the whole front end bounce as it seems too hard ? Does the fork have a rebound adjuster and was it disassembled/rebuild ? Just wondering if a mistake could have been done at rebuild.

ducinthebay · Post by **ducinthebay** » Fri Nov 06, 2009 9:01 pm

The 900 SS that he has is a very limited production bike that was offered for one year before the much more common 91 - 98 SS series. It was sold only in Europe, and Australia. None came to the States.

His bike is what the 750 Sport should have been. 17" white wheels, 320 rotors, 900 motor with 6 speed. Same frame and body work as the 750 Sport, but with a different paint job. Great bike. I have modified mine to be almost identical now.

Fork is a standard variety with no adjustments at all. Same as the 750 Sport, but maybe better valving. Marzocchi M1BB?

Cheers,

Post by **paso750** » Fri Nov 06, 2009 10:49 pm

I know the bike, not its techncal details though.
As it seems the 750/900SS >91 manual isn`t available anywhere on the web anymore so I`ve uploaded it here. In combination with the 750S manual it may be useful.

http://rapidshare.com/files/303349781/D ... -ES-FR.pdf

Post by **jcslocum** » Sat Nov 07, 2009 12:47 pm

G,

You are amazing with the amount of info you have compiled!!

ducbertus · Post by **ducbertus** » Sat Nov 21, 2009 7:26 pm

I've own such 900ss90.
used 15wt oil but was not very happy with the M1BB fork. racing at Assen and cornering fast the fork started to bounce. later I heard that reducing the oil level could help to solve this problem.
playing with the level and thickness of the oil is all you can do. progressive springs are a good investment.
overall it is a good bike.
the Weber carb is a little tricky to tune. problem in the fuel system is the fluctuation in pressure as a good pressure regulator fails and therefore the gas level in the bowl rises and lowers.
I have a workshop manual in hardcopy and a lot of other info.
Over time I've sold a lot of stuff of this bike. At the moment it is a project in hybernation.
I use my 907 nowadays.
If I can do something for you let me know.

Ducbertus

Rebuilding Fork of a 900 SS (1990)

Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)

Re: Rebuilding Fork of a 900 SS (1990)