Guest ratchethack Posted February 27, 2007 Posted February 27, 2007 I think that repositioning the jamb nut will change preload, will have an adverse effect on dampening adjustment, and will change ride height. The adjuster in the cap limits the travel of the narrow damping rod that resides inside the main (threaded) rod. The difference between clicks is quite small so changing the position of the cap in relation of the threaded rod will change the range of adjustment greatly, or negate it altogether. The next time you have yours apart, stroke the rod (not that rod!!) and hold the damper down with your finger. You can feel how much dampening is affected. Likewise with the rebound on the right leg. I'm assuming that rod acts on a valve and the more room it has to travel, the less dampening action because it allows more fluid to flow. Cutting spacers is the only right way (from my limited observations) I have to take a break now the smoke from my ears is starting to block my vision. Dan, it occurs to me that we may well be breaking new ground on this Forum here for Marz 40 riders, and I suspect there's quite a few! May I propose that we approach this as a puzzle that MUST be solved! Speaking for myself, I have no question that I've set up my fork correctly and am entirely pleased. It does NOT by any means follow from this that I have fully mastered its idiocyncracies!!! Might there be a few Forum correspondents who HAVE?? Quite possibly, methinks! If so, we beg their participation in the discussion whilst awaiting enlightenment on edges of chairs across the planet!!!! Leave us now ask a probing question: Wot may be INFERRED from the seemingly obvious intent of the mfgr. by clearly providing a range of adjustability for preload on the cartridge rod assemblies?? Surely it was NOT to allow such convenience while completely destroying rebound and compression damping adjustability in the process!! Must don BOTH the Sherlock Holmes field cap, and affix the Hercule Poirot monocle for this one. . . . Lacking ANY known source of user guide from Marzocchi wotsoever , may I suggest we might well solve this on our own with naught but our own formidable powers of observation and the application of logical analysis! Though Guzzi has provided only one small clue in the service manual, it may be all we need! In my case, since I set preload by re-cutting spacers, and have NOT moved my blue anodized adjusters from their original position 22 mm below the end of the threaded rods, and still have perfectly effective comp & rebound damping adjustability, I'm compelled to ask: Has anyone re-set these preload adjusters to other than the stock position (again, blue anodized jam nut 22 mm from end of the threaded cartridge rod assembly) while following the Guzzi manual instructions to turn the comp & rebound damping adjustment screws full counter-clockwise before disassembly? If so, wot effects, if any, were observed after re-installation on compression & rebound damping adjustability? Based on experience and (I believe) well deserved trust in Marzocchi alone, the Sherlock/Hercule hypothesis: Comp & rebound damping adjustability remain fully functional! In the case that corroborating evidence of others bears this out, we may then ASLO conclude that there is some as yet unknown re-setting mechanism within the cartridges that allows for "zeroing-out" of the fork cap damping adjusters after preload changes via the threaded adjusters. Speculating now, possibly it's designed so that a re-set occurs when the cartridge rod assemblies are turned on the rod assembies as they're screwed back home upon re-installation, so that damping settings may be effectively changed as intended throughout the range of preload adjustability provided!! As noted above, this would account for the conspicuously cryptic (even for Guzzi -- this being our only clue from Mandello!) service manual instructions to turn the damping adjusters full counter-clockwise before dismantling, allowing damping adjustability from any correctly re-set point of preload. Elementary, my dear Watson? If not, wot say you, and by all means -- wot evidence would point to an alternate conclusion?
Dan M Posted February 27, 2007 Posted February 27, 2007 In the case that corroborating evidence of others bears this out, we may then ASLO conclude that there is some as yet unknown re-setting mechanism within the cartridges that allows for "zeroing-out" of the fork cap damping adjusters after preload changes via the threaded adjusters. Speculating now, possibly it's designed so that a re-set occurs when the cartridge rod assemblies are turned on the rod assembies as they're screwed back home upon re-installation, so that damping settings may be effectively changed as intended throughout the range of preload adjustability provided!! As noted above, this would account for the conspicuously cryptic (even for Guzzi -- this being our only clue from Mandello!) service manual instructions to turn the damping adjusters full counter-clockwise before dismantling, allowing damping adjustability from any correctly re-set point of preload. Reset mechanism? Some spring loaded, sprag actuated, over-center triggered switching device? I'd like to see that unit. Frankly, I don't think it's that complicated. I believe the reason for backing out the adjuster before disassembly is avoid damage on reassembly. If the adjuster is cranked all the way in and the cap is screwed on past it's old position you'd likely damage internal components of the dampening valve. I think the key here is the stated 22mm position for the jam nut. This IMHO positions the cap just short of bottomed out and places the rod in the right position for a range of adjustability. The adjuster screw merely limits the floatong travel of the internal rod. (counterclockwise raises the adjuster or stop to allow the most travel (biggest orifice size) and the least dampening. Screwing the adjuster clockwise lowers the stop to limit the travel (make a smaller orifice) and increase dampening. My forks just happen to be off of my bike right now but I may not have time to play until the weekend. I will investigate further.....
Ouiji Veck Posted February 27, 2007 Author Posted February 27, 2007 Curiouser and curiouser.. I've got them on the bench and can't see how the brass adj. screw affects .......anything. The 22mm to the Adj. nut corresponds to the 22mm of "throw" of the threaded "neck" of the cap....thus mating the BAS (brass adj. screw) to the top of the center rod..... It would appear, and I took for granted from the get go, that as you turned the BAS in it would derpress the center rod ... opening/ closing a port. Just to satisfy my assumptions I grabbed my trusty side cutters and tried to depress the rod. I got nuttin' .. I was expecting only 1/8 inch or so but could detect nothing. Next I tried varied leak down tests on the cap itself while I adjusted the BAS (don't ask) I still got nothing. Maybe the BAS gets an imperceptible "throw" on the rod. Lastly..the blue lock/ adj. nut has no more than 1/2 inch of thread below it so you wouldn't get much pre-load out of that and if it was higher the BAS wouldn't seat to the rod. I also played with the BAS while the forks were still together and the effect was easily detectable...so..they do sumptin' ...I still don't know how though..
Dan M Posted February 27, 2007 Posted February 27, 2007 Curiouser and curiouser.. I've got them on the bench and can't see how the brass adj. screw affects .......anything. The 22mm to the Adj. nut corresponds to the 22mm of "throw" of the threaded "neck" of the cap....thus mating the BAS (brass adj. screw) to the top of the center rod..... It would appear, and I took for granted from the get go, that as you turned the BAS in it would derpress the center rod ... opening/ closing a port. Just to satisfy my assumptions I grabbed my trusty side cutters and tried to depress the rod. I got nuttin' .. I was expecting only 1/8 inch or so but could detect nothing. Next I tried varied leak down tests on the cap itself while I adjusted the BAS (don't ask) I still got nothing. Maybe the BAS gets an imperceptible "throw" on the rod. Lastly..the blue lock/ adj. nut has no more than 1/2 inch of thread below it so you wouldn't get much pre-load out of that and if it was higher the BAS wouldn't seat to the rod. I also played with the BAS while the forks were still together and the effect was easily detectable...so..they do sumptin' ...I still don't know how though.. The fluid movement "floats" the rod and the BAS limits the amount of float. I'm assuming the other end of the rod acts on a valve to limit the opening of the valve as suggested above. STOP PRESS Marzocci has downloadable manuals on their site. Sadly our now antique 40mm units are not listed but a current 43USD is. Hopefully this will give us some insight. http://www.marzocchi.com/template/listSPAM...p;Sito=usa-moto Edit: This is clearly a different fork with different adjustments and more studying is needed but if you look at the cutaway view on page 27 of the manual, it appears that the rod acts on a valve as thought. (For rebound only in the 43mm.)
Guest ratchethack Posted February 28, 2007 Posted February 28, 2007 Dan, you did better than I did with your search. I was searching for online manuals and got ZIP, but did not find Marz USA. I registered at Marzocchi USA at the link you provided and requested preferred access to both user and service manuals on the USD 040. The online manual for the 043 fork is of no value WRT preload settings. Though IMHO your most general assumptions WRT damping valve actuation via the rod are safe enough, comp and rebound damping adjustment are enough different on this fork that IMHO there's low probability of relying on common assumptions crossing over to the 040. Will advise. EDIT: Just got an auto response. Reply could take up to 7 days.
Ouiji Veck Posted February 28, 2007 Author Posted February 28, 2007 Yea... I managed to find that PDF over @ Marzocchi too...definately a different animal. I considered the "float" concept too. Good fun while waiting out the last of the winter. Thanks a lot for contributing. After the forks are completed we should have a fairly good reference for sprucing up the 40mm Mazocchis. Just saw ratch...er .. Hercules' post... If he comes up with the drawings it will be great!
Ouiji Veck Posted February 28, 2007 Author Posted February 28, 2007 Ouiji, How about heating the alum before trying to break the set screws free? I'm planning on respringing my front end soon too. I'm going with the Traxxion Dynamics springs because of my weight. If I run into a problem you may hear from me! I shoulda caught this earlier... No...I wouldn't use heat. Who knows what little rubber guys live in there. Probably none but just as a general rule. Same as arc welding...then realizing you've blown an ECU or Anti Lock Brake sys.. Like Ewen McGreggor... (It's so funny when someone else does it.)
Guest ratchethack Posted February 28, 2007 Posted February 28, 2007 Just saw ratch...er .. Hercules' post... If he comes up with the drawings it will be great! Not Hercules, Weej -- Hercule! The Belgian who never waffles. Poirot, Hercule. Supersleuth Private Detective of London, n'est-ce pas?
Ouiji Veck Posted February 28, 2007 Author Posted February 28, 2007 That was a possessive S I know detective Perot......... And if you didn't already have a perfect avitar.....
Guest ratchethack Posted February 28, 2007 Posted February 28, 2007 That was a possessive S I know detective Perot......... And if you didn't already have a perfect avitar..... Ah, but our intrepid Investigator would hasten to point out that the posessive of Hercule is Hercule's, not Hercules'. He'd also hasten to separate his name as far as possible from that infamous hand-grenade with the bad haircut, Perot. More'n slightly irritating's perfectly in character f'er the little Belge. Just like Y'ers Truly.
Dan M Posted February 28, 2007 Posted February 28, 2007 Ouiji, I had time to screw around with this tonight. If your forks are still apart, try this: On the right leg (the rebound adjustment) with the spring out, pull up on the threaded rod with two fingers and feel the resistance and watch the inner rod float up.. Then pull up and hold the inner rod in as you are pulling and feel the increased dampening. When you hold the inner rod in and close off the oil passages the dampening action is increased. Ratch, the 22mm setting on the jam nut insures that the cap is not bottomed out against the threaded rod. On my fork there is not quite 24mm of room before the cap bottoms out. The adjuster in the cap on the '02 model has 20 clicks of travel when the cap is off. There is about .2mm of travel for each click. When the cap is set against the jam nut at 22mm there is only 19 clicks of adjustment. If I were to bottom the cap there would be a fewer clicks due to bottoming the rod against the valve. If less than 22mm was used, the whole 20 clicks would be available but I doubt the first few clicks from the top would make a perceivable change. (too much gap) Make sense? Also, As Ouiji indicated, Poirot's mug with that slick moustache would be a nice change from Marty
Guest ratchethack Posted February 28, 2007 Posted February 28, 2007 . . .Make sense? Dan, the game is afoot! Wot you say makes perfect sense. I've begun to understand that the instruction on this fork that I took many moons ago from a Pro (who frankly, ought to've known better, if my newfound understanding is correct! ) was WRONG. This thread has brought me to the point where I NO LONGER BELIEVE wot appears to be threaded preload adjustment on the cartridge assembly rods is that at all. Though this would be a plausible explanation taken on appearances alone (and lacking a freakin' manual that explains the thing! ) the misinterpretation of this has no doubt brought similar confusion to many, being unmentioned in the Guzzi service and user manuals! Might this have contributed to lots of frustration with many owners of these forks over the years, who screwed 'em up by disabling damping adjustment entirely, doing wot seemed right and lacking guidance from the manual?? Seems to me the correct procedure is to do wot I did in my ignorance -- set the blue anodized jam nuts to 22 mm, just as it came from the factory. Adjust preload by cutting new spacers, just as I did, following procedure from countless damper-rod forks in ages past. Hopefully all will be made clear if/when Marz responds with access to detailed procedure/manual.
dlaing Posted February 28, 2007 Posted February 28, 2007 Ratchet, you may borrow my forks if you wish. And while you are at it, you may wish to map the air spring effect at varying oil levels, if you are so curious and ambitious. Not sure if this diagram helps
motoguzznix Posted February 28, 2007 Posted February 28, 2007 Has anyone re-set these preload adjusters to other than the stock position (again, blue anodized jam nut 22 mm from end of the threaded cartridge rod assembly) while following the Guzzi manual instructions to turn the comp & rebound damping adjustment screws full counter-clockwise before disassembly? If so, wot effects, if any, were observed after re-installation on compression & rebound damping adjustability? I was also fiddling with this fork some years ago and my experience was: The reason why the position of the blue nut is of importance is because of the relation of the adjustment screws to the adjustmentt rod. If you screw it on too many threads, you might not be able to open the damping valve, if you screw it on too less threads, you cannot close the dampening valve completely. This is the reason why the clicks should always be counted from fully closed, the number of clicks depends fron the relative position nut/rod. The influence on spring preload/ride height is minor, as the spacers allow much more preload adjustment.
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