900SS Ie Sport with non adjustable forks - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 17 (permalink) Old Apr 30th, 2019, 4:07 pm Thread Starter
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900SS Ie Sport with non adjustable forks

Evening all.

Browsing through my Haynes book on the above I find the recommended fork oil volumes to be 528.5 - 533.5cc. per leg 7.5 W Fork Oil.

Have had poor compression damping ie at low speed ( walking speed) , most fork travel used up with tie wrap indicator settling about 5 - 10mm before bottoming out.

Removed forks from bike this afternoon and initially I get approx 380 cc collected and with minor spills probably add another few cc. Forks have been dismantled in some vein attempt to find the missing 100 + cc of fork oil. Nothing ...

Bike as covered a very low 3500 mls from new and fork oil removed was almost clear, Stanchions like new, internals like new, seals like new. Previous owner ( experienced rider) had a low speed incident with very minor scrapes on foot rest, front fork lower leg etc etc. In an attempt to prevent the feeling of being ejected over the bars, I have converted to a ABM handlebar conversion......I might add I have had many many bikes over the years but this mid life crisis thing has bitten again so I thats why i bought the Duc. Ridden 900SS Bevels, Hailwoods Reps, owned Laverdas, Harris Magnums in my younger years but having had gaps from riding, a new to me bike will always feel a strange until you get it sorted for you.

Checking the Haynes book again and the specs say for a 600SS ......390cc volume ( Marzocchi Forks ....probably the same forks)

Just wondering if anyone has found similar ??

Is this why the buget 600, 750, and 900 Sports all handled so poorly ??

Suppose the anwer lies in filling to the recommend levels/volumes and tring it but dont want to get into a hydraulic lock situation and drop the thing.

Any specs from someone whos been there before witht his particalr bike will save me much time and aid my longevity.

Thanks in advance
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post #2 of 17 (permalink) Old Apr 30th, 2019, 4:41 pm
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The fork could be a showa , it will say on the cast lower of the leg facing the wheel. If you are not sure take some pictures of the inner lower and post them.

The forks are usually undersprung, over dampened on high speed compression and over filled with oil to make up for the lack of spring. If you want them to work well then start by springing them and then you can lower the oil level. If you keep the soft springs then you can not lower the level safely.
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post #3 of 17 (permalink) Old Apr 30th, 2019, 5:08 pm Thread Starter
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Thanks for getting back to me on this.

Tempted to just fill to the recommend oil levels and see what it does.

I sat on ( not ridden) a 40,000 mls superlight today just for comparrison. The guy told me the suspension was all stock and still had the original fork oil.

It felt ( just sitting on that bike) as though it actually had some dampening ......mine has next to nothing so if there is a 100 + cc of oil missing ( same spec as the factory 600SS) this may be the first step in having some forks that actually work. Will get a few phots done in the morning and post for identification.

Thanksagain
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post #4 of 17 (permalink) Old Apr 30th, 2019, 6:52 pm
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oil is set by level (height) not volume, what year is the bike I can check my manuals to see what the spec for stock is. Be sure the cartridges are bled of air or you will not have dampening of the spring. Yes lowering the level if you have that will increase the air gap and the air spring will be softer, this is why I said do not run lower oil levels if you run stock springs. FYI stock progressive springs are good for about 130lb rider. you can add preload to put the soft portions in coil bind and get onto the stiffer portion but it is truly a bandaid.
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post #5 of 17 (permalink) Old Apr 30th, 2019, 7:44 pm
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what eric says.

my manual says 410ml for the sport. but the height is gives is a copy of the adj section at 108.

oil height has no bearing on damping. damping is oil viscosity based.

has anyone drilled bleed holes in the cartridges?

600ss manual is irrelevant.

know all wanker
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post #6 of 17 (permalink) Old May 1st, 2019, 4:44 am Thread Starter
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Thanks for that

My reference to the 600SS is what the oil volume is specified by Haynes in their manual. Since I drained a similar amount (380cc) my thoughts were .......had someone assembled my particular forks to that spec instead of adding more....hence the search for the missing 100 + cc of oil.

My Bike is a 2008 registered 900 Sport and these were sold off as "Dark " models. They have the steel rear swinging arm, non adjustable front forks and were originally painted Matt Black with either full or three quarter fairing.

Since fork travel or should I say stanchion travel was excessive, the less than adequate dampening oil drained off, I am wondering if the forks were assembled with the cartridges full of air. This would tie in with what ducvet ( eric ?) said as the spring would then have no dampening.

Both front and back end sag both unloaded and with weight of rider on board are about right, however when compressing the forks, there is low resistance to compression ..........and the less than 538cc of oil volume ( ignoring the height for the time being) I would guess means the cartriges were full of air when assembled

I dont appear to have any spring dampening ......again as eric said

" Be sure the cartridges are bled of air or you will not have dampening of the spring"

Think you have nailed it Eric

I will upload an photo or two of the "forking mess" in my garage shortly.
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post #7 of 17 (permalink) Old May 1st, 2019, 6:09 am
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i don't get why people have this need to find an answer, and in the process make up all sorts of possibilities. maybe someone fucked it up, maybe that's how it came. just fix it and move on.

know all wanker
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post #8 of 17 (permalink) Old May 1st, 2019, 6:59 am Thread Starter
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Nice to know the answer to things or is that not progress ......if we didnt we would still think we were living on a flat earth and thinking the other planets revolved around the earth and not the sun.....

Indeed I reckon someone has "forked up" but for mine and others attempting a similar job it would be nice to know what the definitive oil level measurement should be. Haynes. Ducati Dealers all different heights ......

Kinda prevents another fuck up as you put it for me and others.

Just trying to establish a means to "un- fuck it" mate so I dont hit the tarmac like the last owner.

If thats unreasonable then dont bother to answer ......keep your comments to yourself as I am after assistance not a lecture from some "know all wanker"
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post #9 of 17 (permalink) Old May 1st, 2019, 7:00 am
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Some times figuring out the "why" helps prevent you from doing the same thing again. Yes some get wrapped up in the details too much but thats human nature. I have customers in both ends of that spectrum you just need to steer them some times but in the end they are the ones that need to sleep at night.
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post #10 of 17 (permalink) Old May 1st, 2019, 7:40 am
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true, but in this instance "why" relates to something this guy has no knowledge of. who knows what was done previously, and in the realm of stuff we've seen there's often not a lot of reason to be found. we just make it right and move on to the next thing.

like you mentioned, he needs to look at the springs and fix whatever issue is there, then set the oil height to a level suitable for the chosen spring rate. if he fixates on a number in a manual then he's probably not going to get the result he wants.

know all wanker
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