Marzocchi Forks

[knumbnutz]

Howdy everyone,

 

I know the topic comes up a bit but I am trying to find a solutions to fix my forks and specifically the lack of damping.

 

I know reading previous posts, there is a guy in the USA that mods them, but since it will cost at least $1200 to do this with postage, its not a viable option.

 

So I am wondering has anyone used damper kit from a different set of forks - say a griso aftermarket kit or the like ?

 

I am thinking of replacing the entire front end otherwise, because there doesnt seem to be a lot of other choices.

 

Any help would be appreciated especially if someone knows anyone in Australia that can fix the forks

 

regards Neil

[gelos]

What type is your fork, 40mm (to MY02) or 43mm (from MY03) leg diameter? I think for V11 Sport -MY02 with shorter arms is applicable a Showa piece from Aprilia RSV 1000 99-03, brake calipers mount point and triple clamp diameter is the same. Substantial is length of your fork.

[knumbnutz]

40mm.

 

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[knumbnutz]

Ok here's a break down of the internals and fluid ways.

 

 

The is another hole around the other side of the big tube.

 

So the large tube acts as a reservoir of oil and as the rod on the lower left goes towards the right, it compresses the oil which squires out of the holes on the large tube.

Inside the rod, there is another adjustable valve in the tip which is operated by the screw adjuster in the top of the fork.

The screw pushes down on a inner rod the runs down middle and closes off the valve. It can close off completely so the only way for oil to get out is via the large tube.

 

There are two large one way valves that open up as the rod goes back out as the forks decompress.

 

Two ways to make heavier compression dampening. Heavier weight oil or block off a port in the big tube.

 

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[knumbnutz]

 

You can see the hole in the centre of the one way valve

 

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[Scud]

Guzzimoto plugged one of the holes. Here's some discussion of it. 

 

http://www.v11lemans.com/forums/index.php?showtopic=17740&hl=%2Bmarzocchi+%2Bplug+%2Bhole&do=findComment&comment=188893

 

I keep thinking that I will try to do this too - but if you do, please post pictures so I can copy.  

[Tom M]

Have you set your sag to verify that the springs are correct for your weight?  If not that's where you should start.  You might want less compression damping with stiffer fork springs.

[knumbnutz]

Well I'm 75kg or I guess that's about 150pds.

When I took the leg out there was zero compression. Not a bit. Nill.

The springs will be ok.

 

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[knumbnutz]

Guzzimoto plugged one of the holes. Here's some discussion of it.

 

http://www.v11lemans.com/forums/index.php?showtopic=17740&hl=%2Bmarzocchi+%2Bplug+%2Bhole&do=findComment&comment=188893

 

I keep thinking that I will try to do this too - but if you do, please post pictures so I can copy.

That's the path I'm going. Block the hole. If you use thicker oil it will create another issue and that's the inflowing ports aren't designed to flow thicker oil. It may have no effect but it may too.

The other way of blocking the port should be fine.

Funny guzzimoto talks about two ports, mine has three. Not sure but he probably just didn't mention it.

 

I'll post pics, no problem

 

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[gelos]

Hi, from what side is damper unit on your photos? LH/ C compression or RH/ R rebound?

[knumbnutz]

Hi, from what side is damper unit on your photos? LH/ C compression or RH/ R rebound?

L/H side, compression dampening.

[Tom M]

Your compression damper has bypass holes in the outer tube that allow minimal damping until part way into the stroke.  If you have zero compression damping through the whole stroke regardless of how you set the adjuster something is obviously not right. 

 

Here's a drawing that I made that shows the stock damper tube setup and a modification that can be made to increase the compression damping.  I'm not thrilled with the result, I think it's a little harsh on the small stuff even with 5wt oil.

 

 

 

PS I'm 225 lbs and I'm running 1.05 kg/mm springs vs the stock .85 kg/mm so what works for me probably won't work for you.

MARZOCCHI COMP CARTRIDGE REWORK.PDF

[knumbnutz]

 

So the hole is welded shut

 

 

Hard to make out the hole but it's smooth as silk inside

 

Once all back together I'll see whether it works.

 

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[GuzziMoto]

I like what you are doing. I did something similar a long time ago. It was on an early red frame sport.

I don't remember all the details, but what I do remember was that stock it had zero compression dampening until the piston had traveled past the bleed holes in the tube. That was because until it went past the bleed holes none of the fork oil was actually forced to go through the valving in the piston. Once past the bleed holes it went from zero dampening to a lot of dampening. Basically stock it wasn't really adjustable compression dampening but rather an adjustable hydraulic bump stop. You may find that with the mod you need slightly thinner fork oil, but at least the adjuster will have some effect, and different weight oils will let you fine tune it even further.

I spent considerable time with the forks partially assembled without the spring working it back and forth to test the dampening and how the changes I made impacted it. Then, once put back together with the spring in place it was all good.

I should probably open it back up to see how it is doing, Fresh fork oil would not be a bad idea, but too many bikes and not enough time conspire against me.

We just got back from a two week trip to Moab in the Jeep........It was awesome. First time I have ever taken two weeks off at one time.

[knumbnutz]

Thanks GuzziMoto.

I am reassembling them today once I go and get some oil.

Since I have no real experience on the internals I will be testing it in a similar way.

I just did a bike build on a TRX850 and used 2007 R1 forks so I noticed that even one of those legs - which does half the dampening of the guzzi leg - had substantially more dampening. 

So this was a bench mark at the time.

I want a similar stiff setup as the TRX handles bumps like a treat so all things being equal and considering the weight difference, the Guzzi will need slightly harder feel than the R1 forks.

I was going to go down the path of a new front end , but they are simply too hard to come by and since this might be a cheap fix then if it doesnt work, then I can still hunt for a front end afterwards.