M800/620 forks....

[auntymal]

...you folk 'probably know about this however, I have an M800 i.e. (03/04 mod') with the low rent Marzocchi forks. Ok on dead smooth road, totally inadequate in all other circumstances. I've had 'em in and out 6 times, playing with for oil weight, volume and a little internal fettling re the spring pre-load. Ended up getting a total nil result, same old jittery, unresponsive and harsh performance. Was about to grab a second hand set of Showas similar to the ST2 when I mentioned all this to Shaun 'n George at DMoto. Shaun was happy to attemp a 'tune 'n fix', so, what the hell, I'll give it a go, thinks I. On re-installation, and after a ride I can tell you it's "Chalk 'n Cheese/ Night 'n Day", the positive difference is simply astounding! I don't need to replace them after all, it seems the factory settings were completely inapproropriate for local conditions, and Shaun's fix is quite simply the finest most worthwhile mod on my little bike, no question. Not dear to do he reckons its even cheaper when a fork seal blows and they have to come out anyway so the mod could be exectuded then. I could'nt wait though, and now I'm riding the bike almost daily! I can rip over to Wollombi or up Thunderbolts and take the 800 now. For the record the Sachs rear with the soft spring got retired soon after purchace. Now the front works I'm rapt. I pay for my work and this aint an ad but seroiusly if you want a fix for this that will transform your "early injected" 620/800 I couldn't recommend it highly enough. Contact the boys at DMoto on (02)8677 9120.
    

[Two dogs]

So what exactly did they do too them other than oil change ?
Shims , valves ? oil weight change ?

[Betty]

So what exactly did they do too them other than oil change ?
Shims , valves ? oil weight change ?

I was of the understanding that shims and valves were inoperable/non-upgrade-able.

Linear springs and oil weight?

[Wells]

Two main points from that post...

• The Marzochi forks in their standard config suck ass - YUP
• George and Shaun @ DMoto are amazing - YUP

Glad to hear you had such a great result mate - I just got the boys to swap mine out for Dez's old Showas - as you say, chalk and cheese.

[auntymal]

Betty, Two Dogs, likewise I thought, after trying everything I knew, I was facing a big dollar upgrade etc. However "Ignorance is Bliss", I'm just glad I gave it one more try! After all, modern upsidedown forks should be "ok" at the very least, no? Anyway, I'm not an engineer, compared to these guys, anyway. As far as I know, there was no replacement with after market shims or valves or kits. My guess is it would be a combination of oil weight, on the one hand, resulting in a better rebound action, on the other? They adjusted and modified/tuned the std set up so it works as it should have from the word go, so it IS do-able, and very reasonable too. Just exactly how that was achieved is something they know about and were able to do, whilst I could not. One thing is for sure, it works and I'm rapt...
 

[Bazz21]

from my personal experience lowering oil level will let the shock work and give more travel 

[auntymal]

...certainly Bazz, however on it's own it was still ordinary believe me. There used to be virtually zero damping and now, it's pretty darn good. i.e. you can get stuck into it over the rough without getting out of the throttle coz it's so woeful it's about to spit you into the tree tops! I had 6 serious goes at it and was on the verge of being defeated and defaulting to expensive "proper forks" etc... not now.
 

[Bazz21]

isnt it nice  to find somone who fixs things with out the bull shit u want to look after that  business  and to have the passion back for the bike enjoy bazz

[auntymal]

...too true Bazz. I have 214,000k on the ST2, and 16,000k on the M800. Reason being I was either not riding/trying to fix/riding dissatisfied on the 800 etc. In a way it's kinda like having a "new bike".
 

[brad black]

generally all the non sbk springs are too soft.  the st aren't too bad, but at 0.85kg/mm ish they're still 0.1kg/mm too soft for most people.  and they need a heap more preload.

most use a dual rate spring, which needs 80 to 100mm compression to change from the soft rate (0.5 - 0.6kg/mm) to the harder rate (0.85 - 0.95) because the tight wound section has equidistant coils.  there's very little progression in them, and they're just wrong.  if you cut the tight wound section off the remaining open section is usually pretty good.

really, if you have 6 goes at it you're doing it wrong.  while revalving is definitely an experience based thing, getting the right spring in there and setting the preload is pretty simple and based on science.  you just need to expect to replace parts.  people think that ducatis come with high grade components.  but the cheaper ones come with budget stuff to get the price down, and they all can do with reworking anyway.  even the ohlins.

I recall reading something from rick at cognent dynamics about the 43mm marz being as good as or a little superior to the non adj 43mm showa.  you just have to spring them right to start with.

mal's reaction to what is basic suspension work of "it feels like a new bike" is very common, and very frustrating.  sometimes it takes lots of convincing to get a customer to be prepared to hand over money for suspension work.  and when they do they get all born again on you and try to convince everyone else that they have to do it too.  and everyone else acts like they did prior to being convinced.

you'll all spend thousands on bling, but actually spend money to make it a better bike to ride?  pfffft.

[suzyj]

Dunno if all Marzocchis are the same, but mine had different damping in the two forks. One had a compression circuit that only turned on about 2/3rds of the way down the travel. Was really weird. Combined with the excessively soft springs, each time I hit the brakes I'd get that sudden change in damping. I was convinced I was bottoming out.

To say the 998 forks were a revelation is the understatement of the century.

[auntymal]

...I'm with you Suzij....one of the reasons I had 6 goes was that I was making too small an adjustment each time, as far as I know mine aren't the comp' on one side, rebound on the other, type. (Happy to be wrong!). Also, the solution was more complex than "just air gap". As for springing, my std rear was WAY too soft, using all it's travel in static sag before I even let the clutch out. (replaced with a WP and spring). The front however was not too soft, just lacked compliance and had trouble moving through it's 'sweep' when the going got rougher and speeds rose etc. Compared to standard it's "chalk 'n cheese". Satisfied to have my M800 back and enjoying riding it. Never had these problems with the ST or the 996. But they had higher spec jappo Showas. S'pose it's unfair to compare poverty pack spec stuff to more expensive items. Live and learn, I guess...

[brad black]

I had a chat to shaun yesterday and what he did was nothing like I was saying. 

I have one of these legs at work, externally damaged from a m400ie, so I pulled it apart yesterday for a looksee.  the cartridge has heavily swaged ends, but nothing to stop a pipe cutter.  there really doesn't seem to be any function for compression damping, apart from oil being transported through holes for want of a better term.  and a hole in the side for oil to squirt out of.  there is a rebound shim stack.

I'll download the photos from my phone and post them on my blog.  I might try to get back in there to put it back together (tack weld the cartridge) and modify my spring testing rig and do some assembled rate tests for varying oil heights.  maybe throw a linear spring in too, just to get an idea of how it all works as the original will really exaggerate any increase (rate change from 0.63 to 0.91 @ 90mm compression).  some of the modern forks are going to very low oil heights: I've set ohlins by their specs down to 160mm or so.

[auntymal]

...uncertain, my forks are the same as those?

[brad black]

started my report.  I had some fun playing today.  it's always fun learning stuff.

http://bradthebikeboy.blogspot.com.au/2013/12/marzocchi-43mm-fork-design-and-impact.html