[wineguy]

Hi All. So I tried searching various forms of this question but no luck so far. Is there anything to be aware of, or do differently with fork oil replacement when dealing with an air assisted shock? Not sure if that's even the correct wording, but there's a schrader valve on the top right side fork and I figured y'all would understand what I'm saying. I can pretty much push down on the handle bars and bottom out the fork with modest effort so I figured it's probably overdue for a change. Going to drain and replace the (most likely original) fork oil in my 'new to me' 81' CM400C. From what I can tell, it should have about 10-14 psi of air in the shocks. I used my air gauge and got a zero reading btw. Looks like it calls for 137 to 143 ml of oil, I'm using 10W fork oil and figure i'd go with 140 ml.
Thanks for any insights.

Cheers,
Dylan

 

[wineguy]

First question is, what's the best way to remove these?

 

[Gene]

You can remove those with an adjustable wrench or any wrench that will fit it. Standard thread - by that I mean lefty-loosey. I just removed/replaced some of these.

 

[Gene]

BTW - should be 4.6 oz (about 140 ml) per side oil per the manual, which means I grossly overfilled mine and need some draining I used the std 7 oz per side for 70's CB's of which I have two. whoops. Don't do that.

 

[wineguy]

Got it, thanks. I was concerned about those connections that attach the forks to the Schrader valve, as I was loosening them it just seemed to be twisting the rubber section in the middle and I didn't want to damage it. I'm trying to upload a picture but that's not working for some reason.

 

[longdistancerider]

Remove the hose from the pictured side first. You may need 2 wrenches on the large nuts to break it free.

Moved to SOHC Suspension

 

[Gene]

Sorry wineguy - I thought you were talking about the fork caps. What Jim said for taking the hose off.^^^^

 

[longdistancerider]

Also when changing fork oil the fork caps are removed which means there's nothing holding the bike up anymore since the springs are now free. BE SURE to support the front end of the bike before removing the caps!

 

[wineguy]

Also when changing fork oil the fork caps are removed which means there's nothing holding the bike up anymore since the springs are now free. BE SURE to support the front end of the bike before removing the caps!

Thanks for the tips above regarding which side to start on. My plan was to do one fork at a time while on the center stand.

 

[Gene]

BY THE WAY - when you go to drain the oil make sure you've released all the air pressure. I just made a work shirt a rag All part of learning. #ForkOilDontTasteGood

 

[longdistancerider]

Thanks for the tips above regarding which side to start on. My plan was to do one fork at a time while on the center stand.

Center stand only is risky, stick wood or something under the engine as well just to be sure.

 

[wineguy]

Went pretty smoothly for my first time I think. Removed the handle bars and choke to get better access to the air hose that attached the left and right side to the schrader valve. Pretty tight space in the to work. Left out the air before taking off the caps, kept the pressure on the cap for the last few turns so as to not launch the spring when it came loose. Drained, flushed and filled the left side first then did the right. There was some conflicting info regarding fill levels. My manual has it at 140 ml +/- 3 with no mention of whether it is a A/C/T or E model. But elsewhere here this topic is discussed with the C model needing 190 mls and the E model taking 140. Went with the 190mls. Had a bit of a challenge compression the spring and getting the cap to thread back on under pressure but eventually succeed. Re-pressurised to 14psi and took it for a quick ride around the block with some heavy front end breaking, and tight turns. Felt great. Thanks everyone for your advice. This forum rocks.

 

[longdistancerider]

The C model does take 190. 14 PSI is the max air pressure, you can run less to soften it a bit.