Marzocchi 48mm Challenge!

[Jakobi]

Next time you have your forks apart and bleed them up, turn the cart upside down, cycle the rod once or twice, and tell me what happens.

I've been through the bleed procedure more times than I'd like to admit this arv. I'm lucky the missus is still talking to me!

I'll post up the method I used to get the best results, but even then, flipping the cartridge confirmed there was still some air hiding under the ICS piston. The good news is, if you flip it back over and cycle it as you would when initially filling it self bleeds and goes back to performing as it should. I've opened the cart after doing this and its not foamed up. Still bugs me though. I'd like to be able to get them 100% air free.

[Jakobi]

So for reference, my bleed procedure went like this.

Start with PFP adjuster backed right out.
225ml of fluid from the vacuum pump into a measuring jug.
Set the cart in the vise at a 45 degree angle, bleed hole pointed up.
Use same masking tape and cover the bleed hole pointing down.
Shaft extended, pour the fluid down the bottom edge of the cart like you're pouring a beer.
At the same time, stroke the shaft to bleed the oil through the mid valve.
Note: twist the shaft at the same time to allow the bubbles to rise towards the top and create flow through the ports.
Once no more air can be heard/felt through the mid valve, compress the shaft, and set aside.
Repeat for the second cartridge.

Take the first cartridge and mount in the vise the same as step 1.
Compress the shaft into the cart to raise the oil volume.
Insert the base valve so that the valving contacts the oil and rotate to get some fluid into the valve. You should be able to do this without the bottom O-ring seating past the open bleed hole.
Hold the BV, make sure the bleed hole is open, and extend the shaft.
Now push the BV down into the cartridge past the first oring and hold it there.
Stroke the shaft up and you will feel it trying to push the BV back out. Slowly release the BV until the bleed port is just exposed and you will hear it vent.
Note: the o-ring should just allow it to vent as the shaft bottoms against the cart.
Rotate the cart up vertically, and with the shaft still compressed, push the BV down into the assembly. It will force the shaft out as the BV drops into the cartridge.
I use the tool, and a 19mm socket and can get above the cart and push directly down using my shoulder and twist/move my body to engage the threads.
Snug up the compression assembly/BV.
Rotate back to 45degrees, with open port facing up and cycle the shaft, but not deep enough to cause the upper o-ring on the ICS piston to blow past the drain holes .
Set aside to allow the cart to rest and repeat for second cart.

Once it has rested, set it up again in the vise.
At this stage, the cart should be overfilled by 15ml. This is what you will use to purge the air from the cart.
Cycle the shaft up deep enough to push the upper ICS oring past the drain port.
You will hear it discharge any air along with the extra oil.
It will take several cycles to remove the excess oil - and the shaft will not bottom out with the cartridge over filled to this extent without first purging some oil.
When set to correct volume the upper O-ring will sit just visible in the bottom of the drain port with the shaft fully compressed.
Follow up with some very fast cycles using the full stroke to see if you can get any last purges as per GMPs post.
Inverting/Shaking the cartridge a few times (without cycling the shaft) may assist in moving any further air into the center of the piston where it can be purged.
Repeat for second cartridge.

When completed both should behave the same way.

[Vindicator]

Good post . Next time I service my forks I'll check what you ask .

[StuJohnson]

Per Jake's post....

Are you fricking kidding me???

A video of you doing this would be AWESOME!!!


Sent from my iPhone using Tapatalk

[Jakobi]

Speaking with Glenn some more, and when getting to the final steps its important to stand the catridge vertically when purging the air and oil (not 45 degrees). For the final purge/bottom out I always stand the cartridge vertically on a piece of pine on the floor, and use my hand to bottom the cartridge as quickly as possible.

Think I might go and try one more, one more time.

[n_green]

Originally Posted by Jakobi

Speaking with Glenn some more, and when getting to the final steps its important to stand the catridge vertically when purging the air and oil (not 45 degrees). For the final purge/bottom out I always stand the cartridge vertically on a piece of pine on the floor, and use my hand to bottom the cartridge as quickly as possible.



Think I might go and try one more, one more time.

A video would be great.

[Jakobi]

I played some more today, but sorry.. No video

The bulk of the twisting and turning is to just help free any air from within the pistons, inconjunction with flow.

Before you insert the BV use a torch and check the fluid. It shouldn't have any bubbles suspended in the fluid. If it does set it aside and wait for them to surface on their own.

With the base of the IFP, it appears that there is potentially 2 areas where air can get trapped. If you look at the piston you'll see that there is a recess where the shaft is in the middle, a stepped area around it, and then a recess around the outer edge. I believe the step is what is causing the issues and allowing air to get trapped around the outer edge. The inner recess vents through the piston when it reaches the tapered section on the shaft (spring compressed). Stroking the shaft quickly until it bottoms will purge the air and excess oil from this inner section, however does nothing to purge air against the outer edge.

There are a few indicators that air may be present here. If you pick up the cart and shake it near your ear you hear oil sloshing around. Note that this could also be any oil thats been purged and is sitting above the ICS piston.

The challenge is to move the air from this areas over into the middle section, and to do that we need to get flow. Either by physically shaking/moving the cart around. I find rotating the cartback towards a 45 degree and then over some more and cycling the shaft can help flow the oil around, then invert it and complete the fast full strokes again. Repeat. You may find that the cart purges a little more each time. Also take note of the position of the oring on the piston in relation to the port on the side of the cartridge. The aim is to get the o-ring as low as possible where it is only just visible.

Ideally, when completely bled you should be able to change the PFP adjustment and see no change in the height of the ICS piston when the shaft is completely bottomed. You should be able to shake the cartridge around and hear no sloshing/movement of fluid, and if its really good you should be able to flip the cartridge upside down and cycle it without hearing an air gurgling.

Previously I noted that if you continued to cycle the shaft that it would self bleed itself back. Not entirely so. It just distributes the air through the oil so no more gurgling is heard. Comparing this to a well bled cart shows much less damping (noticably fast rebound), for the same given settings (c/r/pfp)

[Simmo737]

Your spot on jake, turned it over, gurgle, turned it back, fast compress, touch more air, very firm bleed. Nice!!

[Jakobi]

I'd like to look at machining a relief into the base of the piston to allow the outer edge to move the air into the center so it can be purged via the ICS shaft. No sure how much material is there to work with though before hitting seals etc.

[wence]

Precisely what myself and my suspension bloke were saying also.
There needs to be a relief as the shaft is too long to reach the indent .
Cheers Mark