Jump to content
Sign in to follow this  

CRF 450 KYB forks not building air pressure after rebuild!

Recommended Posts

hi

i rebuild my kyb dual chamber forks on my crf 450 2009.

changed the oil on both chambers, replaced both plastic free pistons of the inner chamber, replaced all seals, and put new WP vavle air bleeders. everything was by the oem manual no step was skipped.

the oil seems to stay inside. there are no leaks.

 

the only problem is that after rides the forks are not building any air pressure inside.

when i try to bleed the valves after each ride it seems empthy! no air bleeds out.

 

what is the problem?

Edited by shayke

Share this post


Link to post
Share on other sites

Put the OEM bleed screws back in, the aftermarket ones are probably leaking

Share this post


Link to post
Share on other sites

did u try to pump a small amount of air in and test that way ?  you can also soap the valves after putting a little air in to see if they leak

maybe your ride and temps aren't meeting the requirements to build psi

?

 

just a guess

Edited by Zimman

Share this post


Link to post
Share on other sites

did u try to pump a small amount of air in and test that way ?  you can also soap the valves after putting a little air in to see if they leak

maybe your ride and temps aren't meeting the requirements to build psi

?

 

just a guess

....X2

 

Somedays my forks dont build up air pressure...... I release mine before AND after each ride, some days just dont have any after the ride.....

Share this post


Link to post
Share on other sites

will give it another ride or two without bleeding air and report back.

....X2

 

Somedays my forks dont build up air pressure...... I release mine before AND after each ride, some days just dont have any after the ride.....

Share this post


Link to post
Share on other sites

The KYB 48mm twin chamber forks you have aren't designed to have positive air pressure in them. As you ride the seal will on occasion suck outside air in. But not all the time. Some seals won't let air in ever and some will on the first ride. You need to bleed the air out of your forks before each ride at least once a day or the air pressure will make the forks feel harsh.

  • Like 1

Share this post


Link to post
Share on other sites

So, not paying attention to my suggestion about the bleeders leaking? Lead a horse to water but can't make it drink I guess...

Share this post


Link to post
Share on other sites

went for another ride but before the ride i changed 1 of the bleeders to a oem.

so 1 oem and 1 aftermarket wp.

about 2 hrs after the ride and the bike cooled down i bled them both. very little air came out of both. maybe more air from the oem but iam not sure maybe just my imagination.

any way seems like the bleeders are fine and the reason no air builds up like it used to is because the oil is brand new and doesnt catch on heat like the old oil.

Share this post


Link to post
Share on other sites

You are supposed to bleed the forks when warmed up to operating temp, not after they're allowed to cool off, that's your problem.

went for another ride but before the ride i changed 1 of the bleeders to a oem.so 1 oem and 1 aftermarket wp.about 2 hrs after the ride and the bike cooled down i bled them both. very little air came out of both. maybe more air from the oem but iam not sure maybe just my imagination.any way seems like the bleeders are fine and the reason no air builds up like it used to is because the oil is brand new and doesnt catch on heat like the old oil.
Edited by Eddie8v

Share this post


Link to post
Share on other sites

So, not paying attention to my suggestion about the bleeders leaking? Lead a horse to water but can't make it drink I guess...

I thought it was a good suggestion.  a lot of bleeders out there are no good, or go bad over time.  something to also think about is are the changes in weather (barometric pressure to be exact).  Barometric pressure changes will also affect fork pressure. 

Share this post


Link to post
Share on other sites

-update for all you google searchers-

after the rebuild the new oil didnt produce any pressure inside the fork. after 3-4 rides now the pressure is building up nicely.

what i can think of is that the new oil needs couple of rides to proper chemicly adjust itself.

 

the WP bleeders are fine.

thanks for the suggestions.

Share this post


Link to post
Share on other sites

"air pressure is building up nicely".............. you DONT want that. The "nicely" is what you had in those 3-4 rides with NO air in there. That is why you have the bleeders..........to get the air OUT of the forks. Your re-build worked fine.

Share this post


Link to post
Share on other sites

in My experience fork oil takes time to chemically adjust  before it will allow the build up of air pressure

 

 

Stated

 

 

Cliff_Clavin_in_Cheers.jpg

Share this post


Link to post
Share on other sites

I searched Google and to my amazement, found that if you take your fork oil and shake it up before using that this will assist in the time it takes to chemically adjust. It said to "shake continuously for 3-4 mins"............

Share this post


Link to post
Share on other sites

If you put an aftermarket push bleeder on there, you'll probably never build pressure.The bike vibrates, big hits etc are contantly disturbing the bleeder buttons.

 

I agree, if you put the OEM relief screws and o rings back, the fork will probably build air again, and you can bleed them. I dont know why you think this is an issue...its not.

Share this post


Link to post
Share on other sites

Motion pro makes a great bleeder. The forks won't build up air pressure the same. You DONT want air to build up because it will make the front stiffer and harsh. It's the same as raising the oil level.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×