Soggy front end

Hey all,

since I let the rego lapse, I haven't been doing much with the Commando, but am determined to get the soggy Ceriani front end sorted before I re-register the old gal. Not long before I took her off the road I had a panic stop on the bike and it bottomed-out at the front scaring the shit out of me - the slightest bump would have caused a lock-up, so I really need to sort this. Not only that, it seems to be unstable in some corners which doesn't inspire the confidence this bike should impart.

I inquired around a bit about stiffer front springs, but was told that the real problem is that the Cerianis have tapered damper rods. No dampening at the top of the stroke, then rising dampening as the fork moves into the thicker part of the rod. All well in theory. In practice it’s un-damped forks for the first 2/3 of travel then too little too late. One place I talked to told me that they'd worked on lots of them and they are all the same. 100% Junk. I could use a really stiff fork spring to hold the fork up, or graft a set of 20mm cartridges into them and disguise the caps. Alternatively stiffer springs will work OK, won’t break wrists but I won’t get away from the un-damped “floating on the springs” feel in the fork.

Hmm. Not an ideal situation, and I know precious little about suspension - particularly ignorant about front forks, but I wonder if it's possible to "just" make up a new damper rod with a different profile to do what I need it to. Perhaps something not tapered at all? Anyone have any experience with these forks and can comment on how I can progress? I'd like to try and make the best of what I've got here, throwing away the whole front end would only be a last resort. I'm not a wealthy man.

Yes Dave and what I did in Ms Peel's Roadholders and lucked out my guessing on clearances and length of taper, though didn't get best action till power steering fluid tried. Then worked progressive uncanny dampening, very little for about an inch in the middle of pilot seated sag level then another inch a bit tighter, the rest full choking flow of thin rod to bore space. Not much danger to start experiment with full choke as unless full hydro lock up over filling it'd just ride a bit rough but not bounce off path. Might be able to get away with a lot thinner fork fluid too. I sanded my tappers by guess and by golly but could also just scribe or score a very little bit at a length til noticing effect, if over doing it then re-fill with JBW and start again. Alloy is lighter easier to modify than steel rod.

Thanks Steve, guess it's down to getting my hands dirty and some serious experimentation. What "weight" is power steering fluid?

Dave - harder springs on their own will make the bike more uncomfortable to ride. It will hammer your wrists and make the front end bounce and bang over bumps rather than smoothing them out, and when you brake, you will still get dive. From what you write, your main problem looks like lack of compression damping. I had the same problem with the Roadholders on my Commando and the Lansdsowne dampers with adjustable damping helped a lot to minimise excessive fork dive - with the standard springs. If you can graft some cartridges into the forks, that would be ideal. That's what I did with the Cerianis on my Ducati. The result is suspension that actually works.

Dave

Thanks for the input Dave but I've got to confess that I have no idea what "cartridges" are. Is it a complete suspension 'insert' - you gut your forks first and drop the cartridge inside?

davamb said:

Thanks for the input Dave but I've got to confess that I have no idea what "cartridges" are. Is it a complete suspension 'insert' - you gut your forks first and drop the cartridge inside?

Click to expand...

Dave - yes, a complete suspension insert. The cartridges in mine are modelled on an R6 Yamaha and they were made and fitted by Maxton Suspension in England. They stripped the forks and threw away all the old damping components. When I got my forks back, they also gave me a bag of all those old parts. The only external clues are the fork top caps which have an allen buttonhead screw that conceals a damping adjuster rod with a slot for a screwdriver.

I happened to be following this thread on a Ducati forum, Vintage Section. One Australian poster asked if there was a drop-in cartridge upgrade for his forks: http://www.ducati.ms/forums/14-vintage/ ... occhi.html

One of the replies was from our fellow forum member GRM450, who mentioned Steve Wood at Suspension Improvements 3208 0082.

Maybe Graeme will chime in if he reads this post!

I'd be interested to hear how you get on.

Dave

All well in theory. In practice it’s un-damped forks for the first 2/3 of travel then too little too late. One place I talked to told me that they'd worked on lots of them and they are all the same. 100% Junk. ;Quote:

Are Marzocchi forks also junk :?:

Don't think so Berhard, the ones on my Pantah are pretty good.

Thanks again Dave, Graham is a top bloke and very knowledgeable on both Ducatis and Nortons - I'll send him an email.

I've removed one fork and dismantled it. I measure around 15mm compression for 10kgs loading on the spring. This is 0.67kg/mm which accords well with the quoted standard rate for the Norton of 0.64kg/mm, there being a few percent uncertainty in both measurements.

Pics:



The whole shebang with the exception of the rebound check valve. Still battling with the C-clip that retains that bit.



No sign of a damping seal here - it relies on a close fit to the inside of the fork tube. It ain't that close a fit either. Oil would easily bleed past reducing the damping.



This is the only tapered bit I can find. Sits down the bottom of the damping rod. Maybe that's what they mean. Note the brazed-up damping orifices too. What's the go there?

Opinions and observations at this point: I'm amazed that it works at all. With the rebound check valve removed, there's nothing inside the whole assembly. I reckon it's a pretty good candidate for a cartridge.

Thoughts anyone?

Yes, I have fitted my dampers to Austen Keers Laverda 500, The original set up is quite simple with just some small holes doing the work.
Anyway Austen as won this years B.E.A.R.S race with the Lansdowne kit installed,some minor rear end problem..but a good result.
He also won the 500 race with his Lansdowne Equiped manx.
The kit is Not a full monty stacked shim cartridge , but its giving 10 racers [and winners] a better than stock performance..at an affordable price...and 350 road going Commandos.

davamb said:

Thoughts anyone?

Click to expand...

Yes, I think a cartridge conversion would be good. A decent conversion should make the bike so much nicer to ride. The internals look different to my Cerianis. Would you like me to post a few pics for comparison?

Dave

I would suggest you ask our expert Lab for his well respected opinion, or view it on early posting.
or visit www.lansdowne-engineering.com ..ps later version as extra cushions.

Hello Dave ('s)
I haven't see Cerianis like yours before, they look like an old design.
'74 year 35mm Cerianis are very different as daveh has said, and his suggestion of a cartridge is worth investigating and weighing up costs v performance depending what you wish to achieve.
I fitted 650 Pantah Marzocchi internals and stanchions to '74 Ceriani sliders that work well enough for me, but the Maxton set up and the Landsdowne would be far better.
Would be interesting to know what your forks are from?????
graeme

daveh said:

...The internals look different to my Cerianis. Would you like me to post a few pics for comparison?

Click to expand...

Yes please Dave.

john robert bould said:

I would suggest you ask our expert Lab for his well respected opinion, or view it on early posting.
or visit http://www.lansdowne-engineering.com p.s. later version has extra cushions.

Click to expand...

Any and all well-respected opinions appreciated, as always! The Lansdowne looks like an excellent bit of kit John, but I'll have to take measurements of the Cerianis and ask Lansdowne if theirs is compatible. Otherwise I'll just go look for some generic cartridge that fits or is suited for a bike with about the same front-end loading.

GRM 450 said:

Hello Dave ('s)
I haven't see Cerianis like yours before, they look like an old design.
'74 year 35mm Cerianis are very different as daveh has said, and his suggestion of a cartridge is worth investigating and weighing up costs v performance depending what you wish to achieve.
I fitted 650 Pantah Marzocchi internals and stanchions to '74 Ceriani sliders that work well enough for me, but the Maxton set up and the Landsdowne would be far better.
Would be interesting to know what your forks are from?????

Click to expand...

Hi Graeme, thanks for your off-forum feedback. Yeah I think they're pretty old. No idea what they're off, just something the DPO found and fitted and another thing that I've tried to make the best of...

Cosentino Engineering makes a damping cartridge for Ceriani road race forx. Not sure if they'll fit yours, but worth a look. I believe they're only available thru NYC Norton.

Thanks Snorton. Looks good, but not cheap! I'll send them an email and see if they recognise my forks and can verify compatibility.

http://cosentinoengineering.com/index_files/Page405.htm

Had to resort to the Dremel to remove the snap ring in the end, not my favourite way of going about matters. Here's the remaining parts of the check valve:



Apart from what seems to be a less-than-optimal seal between the damping rod piston and the fork tube, I can't see anything here that is fundamentally wrong in a design sense. I don't see any evidence of there being a taper on the damping rod - maybe it's too fine a gradient to be observed though; I'll check it with the vernier calipers at work tomorrow.

Bemused.

Here is the arrangement of components in my Ceriani fork leg (1974).



Some had in addition a plastic piston ring which sat in a groove in the piston and sealed against the bore of the stanchion.

P.S I have tried to get the image larger on screen but without success, having followed the instructions in the Stickie from LAB. Has anyone else had this problem, and how did they solve it?

daveh said:

I have tried to get the image larger on screen but without success, having followed the instructions in the Stickie from LAB. Has anyone else had this problem, and how did they solve it?

Click to expand...

I'm guessing you have your Photobucket upload image size option set to 640 x 480?

To upload larger images, go to you your Photobucket album (log in) , mouse over your username, and select: "Account settings" from the drop down menu.

Then select: "Album settings" from the headline, click: "View upload options" then change the upload size to either "800 x 600", or "1024 x 768" - then: "Save".

Re-upload the image and post the new image IMG code.

Individual images can then be reduced in size (or cropped) if required, by using the Photobucket image edit option, as 800-900 width image size is often big enough.

(Note that lower res. screens will show a cropped image at the 1024 size)

L.A.B. said:

daveh said:

I have tried to get the image larger on screen but without success, having followed the instructions in the Stickie from LAB. Has anyone else had this problem, and how did they solve it?

Click to expand...

I'm guessing you have your Photobucket upload image size option set to 640 x 480?

To upload larger images, go to you your Photobucket album (log in) , mouse over your username, and select: "Account settings" from the drop down menu.

Then select: "Album settings" from the headline, click: "View upload options" then change the upload size to either "800 x 600", or "1024 x 768" - then: "Save".

Re-upload the image and post the new image IMG code.

Individual images can then be reduced in size (or cropped) if required, by using the Photobucket image edit option, as 800-900 width image size is often big enough.

(Note that lower res. screens will show a cropped image at the 1024 size)

Click to expand...

Thanks, Les, I will try that!