M600 Suspension - Marzocchi Forks

[don_matese]

Ok, so after reading up on this site and then reading and rereading the haynes book of fibs I managed to replace the oil seals in my forks without any problems. The haynes book of fibs and the Monster Bible both suggest 380ml of oil in each fork leg, mine only had 200 (left) and 250 (right) when I drained them. The thing I didnt quite understand was that on the left fork the spring had the tighter coils at the bottom and the right fork had the tighter spring coils at the top, is that correct? why arent they both tighter at the bottom or top? should they be? in which case do I take them apart again to flip the springs?

[utopia]

The general rule for all forks is that the tighter coils should go at the top.
I can't say for certain whether or not these forks are an exception, but I think it quite unlikely.
The tighter coils (if present in sufficient number) actually form a softer section of the spring, ie the springs are progressive.
Since the tighter coils will deflect first, they eventually tend to become "close coiled" ie with adjacent coils touching each other.
This part of the spring then becomes dead weight, and its better that this is "sprung", ie on top of the rest of the spring, rather than "unsprung". ....which is the reason for putting it at the top rather than the bottom.

I find myself wondering whether the previous incorrect assembly also accounts for your differing oil quantities, as when the oil levels were measured (and equalised), the extra submerged coils of one spring would have effectively displaced/compensated for some of the oil in one leg.

I speak in general terms though......I've never actually stripped a ducati fork.

[don_matese]

Thanks. Makes sense utopia. I can easily switch it about before fitting the new bars without having to remove them again.

[slob]

Also important to keep both forks fully extended (or at least by the same amount) whilst putting the top caps back on, to ensure the same air spring volume/pressure on top of each leg.

[Flip]

I'll dig out my Factory manual tomorrow as I seem to remember something about one leg doing the damping for Compression and the other for Rebound so that may have something to do with the odd spring fitting and I also know there was something about two recommended amounts of oil or a revised amount which could account for the difference between what was in them (can't explain why they were uneven though) and the quantity listed by Haynes and the Bible.

But either way, as Slob says, the air gap is just as important as the oil quantity.

I take it you are 100% sure they are Marzocchi forks as the Showa ones do work conventionally I know that.

[don_matese]

Im pretty sure its marzocchi forks. Werent the showas adjustible? The spring in my forks is retained by two collets not a nut.

[Flip]

Im pretty sure its marzocchi forks. Werent the showas adjustible? The spring in my forks is retained by two collets not a nut.

They varied a lot with the early bikes plus there are the ones with higher spec suspension such as the 900 which had adjustable forks fitted and both Showa and Marzocchi were used, although I am pretty sure the Showas had that marked on them but maybe someone with them fitted will confirm that.

Mine had adjustable Marzocchi items (which are currently off at Maxton for them to work their magic with). They didn't really adjust and one side did the Compression and the other Rebound so I am sure the un-adjustable ones would have been the same set up.

I am pretty sure the nut Slob refers to is the one at the top of the fork holding everything together- it is easy to compress the fork trying to get the nut started thus reducing the air gap by the time it seals.

[crust]

My 900 came with non adjustable Showas.

The Showa name is cast into the inside of the lower leg just above where the spindle goes through it.

[utopia]

My 750 (yr 2000) also has non-adjustable Showas, and the identification is as Crust says.
If yours do turn out to be Showas too, I'd be interested to know whether the damper cartridges are rebuildable or pressed together permanently like the Marzocchis are.
I'll be stripping mine this winter, but it would be nice to know what to expect to find inside, and whether or not they're worth persevering with or if it would make more sense to replace them with something rebuildable/adjustable.

[slob]

... I am pretty sure the nut Slob refers to is the one at the top of the fork holding everything together- it is easy to compress the fork trying to get the nut started thus reducing the air gap by the time it seals.

That's the one

utopia, all the Monster Showas I've had apart had crimped together dampers, whether adjustable or not.

[don_matese]

i couldnt get the dampers out of the slider/fork end unfortunately so just rebuilt them without looking. I did have a good look at the fork ends though while I had them off and can state they did not say "Showa" on them, they had part numbers, year and month type stamps but no Marzocchi or Showa on them.

The only things I noticed were the following

1. The dampers/rods in both had a small screw hole in the top (we used an M4 - i think- threaded rod to help pull it up while compressing the springs)
2. The springs had an odd set up as already stated
3. Mismatched oils - left leg was green, right leg was red
4. Forks were scored from a previously (bungled) removal/refit - it doesnt take much to clean the yoke clamps before refitting the forks does it?

Overall, it was a much simpler process than I thought it would be, the biggest issue was actually trying to get the front of the bike up off the ground.

[utopia]

utopia, all the Monster Showas I've had apart had crimped together dampers, whether adjustable or not.

Damn......but thanks.
Looks like I can expect mine to be crimped then, when I strip them this winter.
I feel a change of forks coming on.
Great (always look on the bright side) I can get forks with preload and damping adjustments, to play with.

[slob]

just having oil less than two years old in them will make a huge difference

[DrD]

As would a really good clean out and fresh springs to go with that new oil