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Discussion Starter #1
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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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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Discussion Starter #3
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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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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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.
 

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Discussion Starter #6
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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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.
 

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Discussion Starter #8
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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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.
 

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I assume you’re sure the forks don’t leak. If they are Marzocchi, you can stiffen damping using ATF. If you’re under 80 kilos or just trying to fill with something equivalent to stock, try 7 1/2 w . If you’re a lighter rider or you don’t feel like spending for new springs, it will help a lot to use spacers to get your sag in the ballpark. I use pvc because it’s cheap, and easy to work with. Some say use conduit or some type thin wall tubing because the pvc takes up space. I say on these forks that is probably not a bad thing to reduce air volume to reduce bottoming out. At 87 kilos I used ATF and quite a bit of pvc to get sag on the low side, so they were a bit stiff but definitely a big improvement for little money.
 

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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.
I couldn't agree with you more, but some people simply believe that Ducati knows best and changing to what a couple of nut jobs on the internet tell them to do is not wise. You and I may have done this a few thousand times but it is the comfort of knowing that Ducati engineers are way smarter than us and wouldn't it be heresy? I have had conversations in the past on why changing a one size fits all spring for a spring tailored to a riders weight/preference is superior, it matters not if the owner is not willing to take that leap.

Oem is at least safe and you should get oem results, no better or worse than the bike rolled off the showroom floor and if that works for you ....
If the forks were not done properly then the improvement before this owner got them than could be just what is desired. If you are used to riding vintage damper rod forks this should still be better. Paul Thede (sp) owner or race tech once said " the best you know is the best you have ridden" so by that rule if you only ride less than good your expectations are low enough most will be acceptable.

I also do not know the forks he has based on the year listed did not come to the USA so what forks were mounted could be different than what I have played with. I would guess they are Marrzzocci not showas based on the age but only a photo would prove that. Sounds like a base model 800ss we got and 5wt was what I used in them.
 

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Discussion Starter #13
Many Thanks for your words of wisdom guys.

After numerous calls to Ducati dealers and poking about it would appear the Base Line oil levels for my bike ( 900 Sport - Marzocchis - non adjustable) is 108mm. Drained out as I said approx 380ish cc and refilled with 490cc as this is where the oil levels settles. Procedure is half fill, expel air from cartridge by pumping up and down , install large diameter plastic spacer, another plastic spacer + spring. Fix collet, lock 4 sided nut against top cap and screw into top slider. Install back into bike and test this evening.

Just finished and now of jacks and straight away - the bike ... forks feel completely different. There is more resistance to pumping so the suspension feels as though its doing something rather than nothing

As to my knowledge of suspension systems ....limited with bikes but BSc Hons, MSc, coded welder and 20 odd years building 3.5 - 5.0 litre V8 road and competition engines.

Own four cars including a supercharged V8 and twin turbo V8 and a a flat six. My years as a mature student studying taught me that I knew pretty much jack shit ( very humbling) but proved I was able to learn and apply.

I prefer to know how things work as this helps with fault finding.

I now have a base setting and whether this is right or wrong I will find out and modify accordingly to suit my weight/mass and riding style.

Keep you posted of my findings as no doubt there will need to be mods carried out.
 

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Discussion Starter #14
Brief ride out this evening on Norfolk roads and surfaces are worse than bad. Shocking would be a better description...

Where previously I had 100 mm of fork travel I now have 70mm. No high speed stuff but 50/60 mph and the bike feels much much better. Far from perfect but not getting the "half hand stand" under moderate braking and easier to position and place for slow corners/roundabouts.

Static sag 15 - 20mm and my weight about 14 St 7 lbs.

Reasonably happy with the result so far but will need work to make the suspension more compliant. Forks had never been apart before so factory oil levels were way way off.
 

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Hey it happens I have had more than one set of forks show up to my show with not a drop of oil in them. A customer who built his own mv agusta f3 last year was complaining of fork dive on his first outing, you guessed it the shop who sold him the "race chassis" had neglected to tell him they had drained the oil in the forks for some reason. live and learn.
 

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Discussion Starter #17
Zero fork oil .......thats more than incompetent and with life and limb components, checks and double checks should always be performed. Building engines makes you like this otherwise the old night time/after work ......did I torque tat bolt, stud etc etc

Indeed trust no one or suffer the consequences. I say this through experience.....short story

Bought an old Honda 750KZ years ago .......ex dispatch riders bike with high miles . Bike looked a bit scruffy but £400 was a cheap purchase. Checked it over (mostly) - all okay, done the deal and rode it back home. Hit 90 - 100 MPH on some stretches and seemed okay.

New purchase safely home - jobs to do .......

Up on centre stand - chain a bit loose.

Process of adjusting chain tension and bearing in mind a factory endless chain .....some half witted fuck wit had only split the chain and installed a spring link. Since these chains have "o"rings hadnt managed to nip it up to install the outer clip....a chain waiting to fall off or worse......

So Brothers .....the sermon for the day has ended.

Dont want to ruin the fun but anyone else has similar stories a bit of anecdotal can help preserve life ....
 
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