Forks - Mods?

[ducinthebay]

I got a pair of 907 forks for my 750 Sport project bike. I've got them on the bench apart right now, and have a set of seals to install in them. While I have them apart, is there any recommended modifications that I should consider? Is there anything I should look for while I have them apart? Any words of wisdom as I put them back together. It all looks rather simple, for forks, and that's just the thing that will bite me later.

Any recommendations for fork oil weight and quantity in both sides? Same weight for both sides?

Everything looks fine, except the thick brown goo covering everything. It almost looks like cosmoline, but I think its just old fork oil.

Thanks,

[paso750]

I wouldn`t use a fork oil heavier than 7.5. I also raised the oil level a little bit, but that`s just a matter of taste and testing.

G.

[ducinthebay]

I just checked, and ATF is 7.5 wt. So, I will start with that.
Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 7.6
From Amsoil website.

Now, how much do I put in? Is it best to measure the volume before I pour it in, or should I measure the level in the fork?

Thanks.

[paso750]

907ie: 180mm air gap between oil and upper fork edge.
I`d measure the level in the fork. Those syringes used for that don`t cost a lot.
Measuring the volume you put in will only be precise if you disassembled and cleaned the fork before ensuring there`s no old oil in it.

[Tamburinifan]

M1r info:
http://www.ducati851and888.com/showthread.php?t=24

Someone who fiddled:
http://www.bikeboy.org/851workinpro5.html

[ducbertus]

hi,
you can use a set of progressive springs for improved sensitiveness for little bumps. i'm happy about them.
As the right and left leg have different tasks you can use different oils in the legs. the levels should be the same.

ducbertus

[ducinthebay]

Once again, collectively, you guys rock.
Great input, and some great links.
I'm off to play in the garage this weekend with some forks.

Cheers,

[Tamburinifan]

Just pure love, baby.....
& 8 beers.

Please share your results.

[ducinthebay]

I have 2 750 Sports, and I have put M1Rs on both of them. The 'new' bike is just now coming together, so it will be a few weeks before I test ride it, but I will certainly keep you posted of the results. The drilling of holes in the stancion tubes will be a good test.

Since the chance of me actually meeting any of you guys to be able to buy you a beer is slim, I'll just trust in the universal biker beer pay it forward system. This weekend, I will buy beers for all the guys I ride with, and tell them to do the same next weekend. That beer will be passed on from one rider to another, weekend by weekend. Someday, someone will just offer you a beer, and you will accept as if you knew it was coming. its kind of like a pyramid scheme, but a much happier ending.

Marzocchi in one hand, and a micro brew in the other.

Cheers,

[Tamburinifan]

Seems like a plan, ducinthebay!

Stanchion driiling holes is to reduce the stickyness of the forks, to ease flow in them.
I will try that.

& all good loving Pasoists always owe each other a beeer!

[ducbertus]

just an other question to this topic.
are the bearing rings on the stanchion and in the leg still available, because mine are nearly worn and need replacement this winter?

but first my intergallactical beer

cheers,

Ducbertus

[du907]

I'll put in my 2 cents.
The last time I did a winter rebuild on my forks I bought some new OEM forks seals. I put them in and that summer they both leaked. The next winter I took them apart to check them and everything was straight and true. I had a set of newer 900ss fork seals for some reason. I looked up the specs. and the inside and outside diameters where the same. They had a little different shape, not quite as square looking, the rubber tapered at the top. They were also a little taller.
Anyway, I used them. I had to eliminate the washer underneath them to get the height to match, don't know what the washer was for anyway. I have had those seals on my bike for three years now and not a single leak. The moral of the story is: I believe they are more robust than the original ones.
du907

[ducbertus]

I use Ariete seals instead OEM, and as you stated they work fine. the shape is a little different and the metal washer can't be used anymore. I believe it is a kind of support ring.
But the seals are not the problem. I need the slider bushes.

Ducbertus

[ducinthebay]

Ok, so, I took both the 907 forks, and the 750 forks apart on the bench.

The 907 forks have 275mm spring with a 245mm spacer
the 750 forks have 470mm spring and a 30mm spacer.
Both springs are progressively wound.
Acknowledging that they are vastly different spring rates, the shorter spring will be much more progressive than the longer spring.

The travel of the mechanism seems to be the same for both forks, and the lowers are the same length. The stanchion tubes are of course different lengths, with the 907 forks being longer.

Has anyone put the longer springs in the 907 fork? (with a proper spacer to set the preload), or the shorter springs in the 750 fork?
Seems a lot to ask a spring to give 5 inches of travel from a 11" spring.

Thanks for any insight.

Cheers,

[ducbertus]

I use White Power progresseive spring without spacers.
this is a very good combination. you have to play a little with rebound dampening to get the best out of it

ducbertus