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Bleeding Showa Chamber

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I'm helping my son replace the seals on his 2004 CRF250x Showa forks. As per the service manual, We pull the cartridge and drain the tube. We extend the rod, fill with oil, proceed to pump, pump, pump the rod to bleed the air, then fill the oil to the proper level and reinsert the cartridge.

At this point all seems right, as the rod extends on its own when compressed. Now, following the service manual, we pump the piston rod to full stroke and drain the extra oil from the oil hole. However, it seems like much more than 17cm3 of oil comes out. And once drained, the rod will not extend on its own more than and inch.

Something certainly isn't right. What am I missing here?

 

5a08630b93f09_CRF250X_Forks.jpg.422f23406863178f056beb490794a502.jpg

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By not extending out more than an inch, would you have forgotten an o-ring or seal on the ICS piston?

(not building any pressure)

 

As for bleeding, here's my experiences:

 

Those forks often suffer from bad ICS piston seals and/or bad cartridge rod seals.

Mine and a friend's both had worn internal seals and despite proper bleeding would

have mushy damping within a few hours of use until they were replaced.

 

I've never bothered to measure the exact amount when filling the cartridge, say about 1" below the purge holes

(hold the base valve assembly next to the tube and figure the oil height required to cover the ICS piston)

Slowly cycling the rod in/out only 5" or so, pausing, tapping the sides of the cartridge with a plastic screwdriver handle

to dislodge any bubbles clinging to the sides.

 

Once the base valve assy screwed in, first purging vertically the excess oil,

then a few more times horizontally to empty the ICS spring cavity.

(lay the cartridges down a few minutes on a shop towel so excess drains out the purge holes)

 

Properly purged and with good seals, they should extent out by themselves until about the last 2" of rod travel.

If the rod gets 'sucked' back in when you extend it or, hear excessive 'guggling' of the oil, it's usually a sign an internal seal is bad.

Edited by mlatour

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1 hour ago, mlatour said:

By not extending out more than an inch, would you have forgotten an o-ring or seal on the ICS piston?

(not building any pressure)

Quote

Properly purged and with good seals, they should extent out by themselves until about the last 2" of rod travel.

If the rod gets 'sucked' back in when you extend it or, hear excessive 'guggling' of the oil, it's usually a sign an internal seal is bad.

I haven't removed any seals or o-rings, which makes me think they're just bad. The strange thing is that the pressure is maintained and the rod auto-extends as expected before I drain the (extra) oil from the tube. Is this normal?

This is my first attempt at working on forks, but something definitely seems to be wrong. I'll look things over more closely and see if there's anything out of place.

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Yes, when initially 'overfilled', right after installing the base valve assy but before purging the excess oil out,

the rod will extend out more readily by itself.

 

Upon the first bleeding, with the extra oil inside the rod will have more resistance thru the stroke.

After the excess has been purged, the resistance will be more progressive as you reach full stroke.

Edited by mlatour
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I took everything apart, and I don't see anything out of place.

Just to clarify, are the visible seals on this cartridge the parts we're taking about? I found other threads on this subject, but none of the pictures will load.

IMG_20171112_230900.jpg

Everything I'm reading states that Honda recommends the replacement of the entire cartridge, rather than replacing individual parts. Apparently drilling is required, but I'm struggling to find good instructions.

I'm not sure what the seals would cost for this, but the new cartridge, #15 in the link below, is $90. I'm starting to think i might be better off just buying the new cartridge.

https://www.partzilla.com/catalog/honda/motorcycle/2004/crf250x-a/front-fork

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The seals I mentioned earlier are not shown on any Honda parts microfiche or service manual so aren't sold 

by Honda as replaceable items, they must be purchased thru a suspension specialty vendor like Factory Connection, Race Tech etc.

 

It is highly recommended you only use the OEM seals (NOK brand) and not an aftermarket 'equivalent'.

They are about 15$ each for both types so a total of 60$. 

Buying assy. #15 (90$ X 2) would only fix half the usual problematic issues in these forks.

 

Yes drilling out of some peening/staking is required but quite easy,

it's actually the ICS inner seals that can sometimes be a challenge, especially removing the small circlip.

 

Here's a YouTube how-to video, at 13 minutes in the guy uses Vise-Grips to un-screw the base assy, no doubt damaging them.

You can wrap some electrical tape over the jaws to prevent damage yet still have enough grip. A bit of heat as well as that may have Loctite on the threads.

 

Edited by mlatour
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The seals I mentioned earlier are not shown on any Honda parts microfiche or service manual so aren't sold by them as a replaceable item, they must be purchased thru a suspension specialty vendor like Factory Connection, Race Tech etc.

 

It is highly recommended you only use the OEM seals (NOK brand) and not an aftermarket 'equivalent'.

They are about 15$ each for both types so a total of 60$. 

Buying assy. #15 (90$ times 2) would only fix half the usual problematic issues in these forks.

 

Yes some drilling out of some peening/staking is required but quite easy,

it's actually the ICS inner seals that can sometimes be a challenge, especially removing the small circlip.

 

Here's a YouTube how-to video, at 13 minutes in the guy uses Vise-Grips to un-screw the base assy, no doubt damaging them.

You can wrap some electrical tape over the jaws to prevent damage yet still have enough grip. A bit of heat as well as that may have Loctite on the threads.

 

 

Listen to mlatour. His info is correct. I’ve also had to replace my cartridge seals. It’s not really a big deal. Yes. Avoid the vice grips. The shaft must remain smooth so the ICS piston seal can seal properly.

 

Most suspension shops will sell the seals. OEM only! I know first hand what a waste of time aftermarket seals can be.

 

Follow mlatour’s advice. You’ll be glad you did.

 

Good luck!

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Thanks for all the great info!

I contacted my local suspension guy. He should have the seals in stock and will sell them to me for $12 a piece when he's back in the shop tomorrow. I'll keep you updated.

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On ‎11‎/‎12‎/‎2017 at 10:06 AM, jimmym said:

Now, following the service manual, we pump the piston rod to full stroke and drain the extra oil from the oil hole.

I found this step to be the problem, especially if you don't have the bottoming cone threaded onto the damper rod.  If you push the damper rod fully into the damper body then you will have expelled too much oil and the rod will not fully extend afterwards.  I can't remember exactly how much of the damper rod should be still exposed but it's at least an inch.  The bottoming cone piece will limit how far the rod will go into the body but IIRC I didn't push it all the way in to where the cone makes contact. 

I also bled the chamber with the damper assembly vertical so any last air bubble would be expelled as well as the extra fluid.  Even if you don't completely bleed the chamber of every last cc of extra oil, it will still bleed it out if the fork bottoms fully.  Only a small amount of inner chamber oil will be added to the outer chamber, should create no issues with the air gap/air spring.

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On 11/12/2017 at 10:06 AM, jimmym said:

I'm helping my son replace the seals on his 2004 CRF250x Showa forks. As per the service manual, We pull the cartridge and drain the tube. We extend the rod, fill with oil, proceed to pump, pump, pump the rod to bleed the air, then fill the oil to the proper level and reinsert the cartridge.

At this point all seems right, as the rod extends on its own when compressed. Now, following the service manual, we pump the piston rod to full stroke and drain the extra oil from the oil hole. However, it seems like much more than 17cm3 of oil comes out. And once drained, the rod will not extend on its own more than and inch.

Something certainly isn't right. What am I missing here?

 

5a08630b93f09_CRF250X_Forks.jpg.422f23406863178f056beb490794a502.jpg

 Does anyone actually use step 14 or 15? I'm just curious,  never popped the vent on one to purge but I've also never experienced any problems from not doing so, aka excess oil in the free floating piston (KYBS) or in the chamber of the Showas.

P.s otherwise I use the same method as MetricMuscle.

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I drain, but not with air. Any remaining fluid here adds to the outer chamber oil volume. Since I can’t measure the residual here, I drain it and add the volume I desire to the outer chamber.

 

 

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On ‎11‎/‎12‎/‎2017 at 10:50 AM, mlatour said:

Properly purged and with good seals, they should extent out by themselves until about the last 2" of rod travel.

If the rod gets 'sucked' back in when you extend it or, hear excessive 'guggling' of the oil, it's usually a sign an internal seal is bad.

It was my understanding that the damper rod should fully extend out of the body, by itself.  If this doesn't happen then the chamber is not completely full of oil or air has gotten in.

 

On ‎11‎/‎13‎/‎2017 at 1:28 AM, mlatour said:

Here's a YouTube how-to video, at 13 minutes in the guy uses Vise-Grips to un-screw the base assy, no doubt damaging them.

Pretty good video on these two mysterious seals so many of us have never actually seen.

I'm not too keen on using Vise Grips unless the part can handle the damage.  How do y'all go about removing the Base Valve assembly without using Vise Grips?  I haven't attempted this yet.

A couple of other things I thought kinda strange.

-  He jumps right in to do maintenance on his forks but hasn't revalved them.

-  He uses RED Locktite on Aluminum parts.

-  He don't cuss much for an Infantry Soldier.

Edited by MetricMuscle
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Neither my YZ125 KYB forks or the 2 sets of Showa I regularly service extend all the way out by themselves. 

Early in the stroke the ICS spring isn't compressed so there is no internal pressure pushing to extend the rods out.

 

I think about the only time they can extend fully on their own is if the oil is overfilled and excess not purged out.

Edited by mlatour

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Pretty good video on these two mysterious seals so many of us have never actually seen.

I'm not too keen on using Vise Grips unless the part can handle the damage.  How do y'all go about removing the Base Valve assembly without using Vise Grips?

 

I’ve used a repurposed gun tool. We made pointed pins which clamped into the bleed holes to hold the shaft without damage. I also have split aluminum clamps from Race Tech which have half circle cutouts to firmly hold the same area.

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On ‎11‎/‎15‎/‎2017 at 1:11 PM, mlatour said:

Neither my YZ125 KYB forks or the 2 sets of Showa I regularly service extend all the way out by themselves. 

Early in the stroke the ICS spring isn't compressed so there is no internal pressure pushing to extend the rods out.

 

I think about the only time they can extend fully on their own is if the oil is overfilled and excess not purged out.

I thought I had read where some folks, when disassembling their forks for maintenance, will check to see if the damper rod extends all the way out by itself.  If it doesn't, there is likely a seal leaking.  If air has gotten into the inner chamber then the damper rod will pull back into the inner chamber after being fully extended.

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May be a bit fuzzy on this as it's been awhile. I believe I ground down a combination wrench nice and thin to loosen the shaft locknut and unscrew the cap. Taking the piston off  that way seemed easier with less risk for the diy selfer. Now getting the seal out of the piston with out damaging anything......that's the challenge.

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I think about the only time they can extend fully on their own is if the oil is overfilled and excess not purged out.


The only time I see the damper rods extend firmly to full extension after bleeding the cartridge is when servicing my friend’s Showas with spacers shortening the travel one inch. The shorter travel does not allow the free piston to move as far down the BV Shaft, thereby effectively preloading the pressure springs. My guess is the preload is equal to about 1/6” since they are R model forks with the larger (14mm?) damper rods.

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Thanks for all the help! As mentioned earlier in this thread, this process was much simpler than expected, it just took me extra time as I was meticulous about doing it right.

Here are a few notes I captured from my experience:

1. Definitely do this yourself! The most difficult part of the process was removing the circlip. If you feel this process is too difficult, you probably shouldn't be servicing your own forks.

2. One of the videos I watched mentioned to drill between 2 and 3mm into the cartridge. I clearly drilled too deep on my first attempt following this suggestion, but nailed it perfectly on my second. Btw, i measured the actual depth @ 1.56mm.

3. My local suspension guy was happy to sell me the seals. He didn't act strange that he wasn't servicing my forks this time. In fact, he gave me a few pointers to make the process smoother. His price was fair, and I'll be going back to him for seals and bushings in the future. I love to support my local shops.

4. If you plan on servicing your own forks - buy the tools. Get the seal slider and the fork wrench for your forks. They just make the job easier.

5. This process helped me understand the inner workings of my suspension. I could probably replace the seals and bearings in both forks in about an hour after digging into it like this. In fact, for my next trick, I may even delve into revalving.

Thanks again for the help and suggestions! I can't express how much I appreciate the time and energy spent providing detailed instructions and links. I love working on my bikes, but it's so much easier now with help like this.

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