I've been playing around with my suspension a bit...

I have a sneaking suspicion that the front fork spring preload sleeve [part no. 26 in the Duc manual] has been modified by a previous owner...
I think the ride height is too high...(and maybe the spacer has been replaced at some time - with a longer one)

the tube (grey plastic) above the spring is 245mm long; I'd be interested to know what you guys have or if any of you have played with the preload spacer length.

does this sound right?

Can't help exactly with spec but this I think is somewhere in our documents sections I do have the full transcript (not a lot more).

But this may give you some measurements to be going on with?

As you can see the springs are different and also come in various sizes by the look of it and to add to that you may have a part added that isn't actually shown in the parts breakdown manual!!!!!

GENERAL INFORMATION
The right fork assembly controls rebound (knob at the bottom of the fork slider) and the left fork assembly controls compression (no control anywhere).

Different levels and different viscosities of oils can be used to suit conditions. This is the beauty of these forks. Adjustments on each leg will not effect the other. Only fork springs and oil levels need to remain the same. Oil viscosity can be varied on each leg if you are competent enough to judge and appreciate the differences.

Fork Springs
There seems to be misleading and inconsistant information on the springs for the M1R forks. There are 2 springs, one in each leg. Some parts breakdowns will only show one and even Marzocchi literature is misleading when it actually shows NO SPRING in the crossection of left fork tube. Trust me.......there ARE 2 springs.

Marzocchi has different fork springs for the 42mm M1R forks which are:
Light Spring-------30 inch/lbs---------Part # 18.0071
Medium Spring ---40 inch/lbs---------Part # 18.0072 (standard)
Heavy Spring-----50 inch/lbs---------Part # 18.0073 (standard)

Progressive Suspension has springs (Part # PS 1130). They work extremely well especially with the adjustable preload caps (no Part #) on pg. 7 of the Pro Italia, June 1994 catalog. These adjustable caps were made for the Ducati 750 Paso and the 907 Paso.

38mm tube models should have 160 mm of air distance from top
42mm tube models take 170mm of air distance from top.


The right fork leg with the knob down on the bottom is for REBOUND and has 4 (yes only 4) positions. You can rotate past 4 and will go back to 1 after you get the oil and spring(s) installed you should be able to tell the 1 position from the 4 position.There are different springs in the REBOUND adjustment (knob area) to adjust the range of rebound dampening rates (not to mention you can play with oils).

Light rebound: Spring # 71.0050
Medium rebound: Spring # 71.0051 (nromal)
Heavy rebound: Spring # 71.0052 (normal)



In March 1986 a Marzocchi service bulletin recommended:
Left tube: drilling a 6mm hole, 65mm from the bottom of the fork tube
Right tube: drilling a 6mm hole, 35mm from the bottom of the fork tube.

thanks for that

my (limited) understanding is that the fork should compress approx 25 - 30mm from full (unloaded) length to "rider-less" condition.

I'm getting less than 10mm (give or take with "stiction").
it is also annoying because the headlight beam is up in the air...lol. (only at night, though).
it is handy for spotting possums in trees.

either the fork springs are the higher rating or the pre-load from the spacer length is too high.
I didn't want to cut the spacer tubes unless I can confirm a "standard" length (and wasn't sure how much to cut, anyway).
I'll check the local hardware shop for similar strength PVC tube availability and start chopping then...

Actually, the correct lenght of the preload is whatever it takes to get you sag correct, but a 245mm spacer is huge. The ones in my M1Rs are less than 50mm. The preload is user tunable item, which is why most current shocks and forks have some accommodation for that. Sit on your bike with all your weight and mark the location of the fork tothe slider. Get a friend to help. A zip tie on the fork tube works nicely. Then get off the bike and yank it up on the side stand to unload the suspension. Measure the travel of the fork. That is the sag. Here is a good article that describes how to set up your suspension. http://www.strappe.com/suspension.html
What works for one guy, may not work for another. Take your time. take notes.
The magic order of suspension set up.
1. correct spring rate (stock is probably OK if you aren't too heavy, or light)
2. Sag (preload) this will make a huge difference.
3. compression damping (adjust with oil changes)
4. rebound damping (adjust with knob on the fork)

Front and rear should have equal travel, and move at the same time when you drop onto the saddle.

After that you can play with ride height of the shock and fork.

A good suspension shop is well worth the time and money. Most local shops will do a quick tune for about $40-50, and give you recomendations for changes that you can then do on your own.

If your headlight is in trees, but the suspension is where you like it, adjust the headlight.

Cheers,

just checked a spare preloader its 245mm long

I don't know that I'd shell out for the adjustable units...I have some on my 900SS (but have never needed to play with them)

the tube is almost identical to some electrical PVC at the hardware shop - so I might chop a few lengths and play around.

Given the "standard" length appears to be about 245mm I think I'll chop off about 20mm for starters (~220mm lengths) (which is about how much remains up out of the fork tube sitting on an uncompressed spring)...
these are rising rate springs - and I think the preload length is taking out all the "softie" out of the spring.

I'm not looking for a feather bed ride...and don't mind some dive under brakes (there's alomost NONE now)...but am interested to see how the minor change in front ride height affects the rake and stability and cornering...without inducing gravel rash.