2008 crf450r damper rod doesn't bleed or fully compress

I'm rebuilding my front suspension on my crf450r...Showa twin chamber...and when I fill inner chamber, insert and tighten cartridge and try to compress damper rod into body to bleed out oil it stops 3/4 of the way and won't drain. No matter how hard I push down it won't give up any oil out of the bleed holes. When I took some of the oil out the rod went in further but stopped again before full compress.

The damper rod has healthy extension and extends fully. Any ideas what is wrong?

If you post a picture of the type of piston it has I might be able to help

Here is a picture... Clickers were all the way out too


I'm going to make some suggestions

1/ check mv piston band for wear

2/ check ics piston also called free piston. It should have two bushings and a seal, for wear

I'm gonna venture a guess that the ics piston isn't moving freely which is why the excess oil isn't escaping the chamber. Tough to diagnose without looking at it. Maybe I'll get you pointed in the right direction

Thank you! I'll pull the cartridge out tomorrow and take a look at it and match up your recommendations to the service manual to ensure I'm looking at what you outlined. I'll take a close up pic to see what you think. Thank you again...much appreciated!!!

ImageUploadedByThumper Talk1439439629.616616.jpg

I couldn't wait...here's the assembly....see anything?

If the free piston is right under the spring it moves freely

That's one of the worst piston designs. Too much stiction. Might not allow you to overfill the cartridge on assembly. At the top of the aluminum shaft is there a taper?

No taper. I tried it both with the top plug bolt on and off with no effect...I figured as much. When I took some oil out it came very close to bottoming out but never went all the way. It's weird as the piston moves and seals look ok. Am I going to have to just put in the exact oil amount and assemble? It seems that something is wrong and needs to be fixed...should I replace the entire fork cap assembly?

I think you are right about stiction being the problem. I'll research this and see if there is a solution too.

No you must have a system that blows off excess oil ,as the cart fills from the bottom seal when in use ,if it doesn't burp it will explode the cartridge walls out

Mog I completely agree. My personal experience with this piston design is that sometimes they stick or bind which makes it difficult to relieve excess oil. You can only overfill them a very small amount compared to the older style bv assemblies that have a tapered shaft

Edited by tmsuspension

Try to pull the bolt to one side and wiggle it when you get resistance.

On some carts if you merely push straight down some will hydro lock.

I ended up putting just enough oil to get close to fully compressed and it bled out the little extra in the cylinder. Not sure what it is but I'll try that next time I rebuild.

As posted by others, your ics piston gets stuck probably on the same position.

When ics is inserted, spring is preloaded by floating piston.

So up to a specific height it can freely move.

Less oil =less preload = more travel (stuck point is higher)

More oil=more preload=less travel.

Travel of floating piston and rod related to one another.

Floating piston either stucks on wall or or on inner rod.

Is your bleed port open? ( hydrolock)

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