hardinge915

my 2005 Marzocchi Dirt Jam Pro forks have a severe case of top-out. I have the correct amount of air pressure in them and all is set up well. Although i cannot get rid of the top-out. Any suggestions?
Cheers

Maelstrom 

Is this occuring during lots of high speed bumps?

Kidafa

Top out.... what a BI*C*........
Everyone will experience this sometime in their riding life...
I have had this problem with my Stratos MX 6's and my Rockshox Boxxer teams....

Some reasons for top out:

1. All the internals are not in the best condition
2. Your pistons in the fork are not the correct size, could be off by acouple of mm (May have shaved themself's like a mates RST's)
3. You are not running the correct amount or weight of oil in the side of the fork with the dampening rod
4. Internals have not been put together properly

These are just SOME of the reasons for top out...
Sometimes cheap forks do it and sometimes you get a dodgy set from a main brand eg. rockshox and marzochi.

If you are willing to rebuild your fork that is what I would do or take them down to your LBS (does LBS count as aol talk and not being alowed?) and get them to rebuild them.

Hope you find the problem and fix it. Keep us posted becuase everyone gets top out..

Maelstrom 

Also, if it is occuring during high speed bumps, next time buy a higher end fork. Djs have specific damping to ONE big hit. Once you start adding the hits up it is not a fast enough damping system to maintain proper oil flow. There are options to fix this such as drilling a slightly bigger oil hole in the piston.

hardinge915

ok thanks for all that, and no its not only high speed bumps, its also wen i do small jumps and drops at low speeds, though i drop nearly 2m they never bottom out, only top out. they are only a bit over a week old so they cant be wreked(i hope not anyways) but ill take them back to my LBS and ask him to put more oil in. Cheers

cryogenic

it's not so much the AMOUNT of oil, it's the weight.. basically if the oil is too thin, it won't provide enough resistance and the piston will just slam right through it and top out. Heavier oil will provide more resistance.

hardinge915

ok, since mine is air in the right and coil in the left, if that normal for both shock arms to be differnt compounds inside?

Maelstrom 

a) could be too much air. Those shocks are really sensative to air pressure. Drop 5psi per leg maybe. This is something you can pay with. Simply release a tiny bit of air per leg.
b) You could, in theory, have too much oil OR as cryogenic says, your oil is too thick OR both.

Try the air first. Would be cheaper than getting someone to rip your fork apart.

hardinge915

thats the problem, my right hand fork arm has the air pressure valve, where the other leg has a compression setting for the coil. so could it be either too much air and too thin oil resulting in my problem? cheers

Maelstrom 

You are having an issue using the travel, correct? I would think you have standard 7.5 wt oil. Make it thinner.

But before that, remove all of the preload in the compression preload and try it. Then remove a little air and try it. You likely won't have to change the oil. You may find for your weight the springs + compression preload + air preload = too much for your weight.

I can run a 2004 dj2 with air preload pumped up and have a hard time bottoming the fork with medium springs. I am 270...that should tell you something about how stiff those fork feel. They are meant to feel like a rigid with some give and only under the most extreme circumstances will they 'give'...

cryogenic

according to Marzocchi, top out is remedied by increasing oil viscosity. Obviously there could be other factors, but by increasing the oil's viscosity, it will keep the piston from moving back upwards so quickly once the coil and air springs reach their maximum compression and start to rebound. Installing a softer coil spring and/or reducing air pressure in the air cartridge will allow more downward travel and won't rebound so harshly. Going with a lower weight oil will actually contribute to top-out, so I wouldn't recommend going that direction with things. You'll know you've gone overboard on the rebound damping when the fork starts to "pack up" (stays down and rebounds very slowly) over multiple smaller impacts.

Maelstrom 

oil viscosity = expensive. Preload will almost do the same thing and really too much preload shows those exact symptoms (this is from personal experience not marz manual).

Oil is a last resort in my life. And in fact I have been able to fix every problem I have had by other means (although I did drop oil height at one point)

anthonaut

Nope. Use it all you want.

hooligan

Adjust it to be less soft and plush. I was test riding a hardrock with a gila, put iton its softest settiing and it was Major Topout. Then I made it a little less plush and there wasn't as much top out. Fiddle with the adjustment. Speaking of adjustment, MZ RACE's adjustment screws dont do ANYTHING. They seriously SUCK.

hooligan

Also, my friend got a Dj3 fitted with z1 internals. It's still a 4'' fork though. Would it plush or rigid like? Is it the structure that makes it rigid or is it the internals?

a2psyklnut

Please explain further. A new quart of fork oil, (which I buy from a MX shop) runs me about $4.00 a quart. A quart lasts about 3 rebuilds.

I'm a bit cornfused????

BTW, I change the viscosity in all my forks to 10 wt. from the stock 7.5 wt. Takes about 15 mins. start to finish.

Maelstrom 

Oil isn't expensive. The labour is. Most people (myself included) do not change the oil in their own forks

a2psyklnut

Why not? It's super easy!

Maelstrom 

In this particular case, with the slider and the z1. I am lazy. For me it seems like, potentially, the messiest and most tedious thing to do on a bike

a2psyklnut

When I buy a new fork, it's the very first thing I do. I get an old 2-liter bottle of coke/pepsi/whatever, and cut the top of it off. I unscrew the top-cap, remove the spring, drop it in the bottle, and then pour the oil out, tilting bike over so any drippings fall AWAY from the bike. Remove your front wheel and take a plastic grocery bag and wrap your caliper. Let all the oil pour out, then wipe down with a clean rag. It doesn't have to be perfectly clean since mixing the oil won't be that big of a deal. Like changing the oil in your vehicle, whatever oil is left clinging isn't an issue.

Then do the same thing to the other side. Once both sides are done, then replace the oil. I take a zip-tie and loop it. Then I measure the necessary oil height by cutting the zip-tie to the proper length and using it as a dip stick. I also use a cheap graduated cylinder to use the proper volume and use the dip stick to double check. Remember since the oil is viscous it will stick to the graduated cylinder so you have to add just a bit more to get the proper volume.

Plus, since I'm bigger, I add just a bit more to firm up the ride.

Seriously 15 to 20 mins start to finish. I then take the old oil to the auto parts store for recycling.

Maelstrom 

I have an old fork I can play with. I will try this out. Good instructions a2, you sure make it seem easy.

bikered

a bit dumb, but....
whats the difference between top out and bottom out?!

Maelstrom 

top out is when the fork uses a part of the travel before it stop moving
bottom out it blows through all the travel

hardinge915

yeah thanks for all the help and contributions to my problem. I have playedaround with the preload adjuster and it didnt make a difference. As i decrease the air pressure and harden the preload they bottom out easily even with the preload set as 'hardest'. So when i put the correct amount of air pressure in my forks, there is no bottom out though top out. The current oil is SAE 7.5(manual), should i upgrade it to 10?

Maelstrom 

put a little less air...don't drain it...sheesh. If the proper amount is 50psi...drop it to 35 or 40.