Go Back   Motorcycle Forum > Motorcycle.Com General Discussion > Motorcycle General Discussion

Thread Tools
Old 09-23-2011, 06:46 PM   #1
Registered Member
Join Date: Sep 2011
Posts: 12
Default fork question..

so my front forks have been soft or spongy since i bought the bike, so i put in new fork seals and dust wipers thinking (or not thinking) that they were air filled. question is how much fork oil should be in there, how do i check it, how do i drain the old, fill with the new and fix it....thanks..

its an 81 cm400 custom
racefan is offline   Reply With Quote

Sponsored Links Remove Advertisements
Motorcycle Forum
Old 09-24-2011, 01:44 PM   #2
Founding Member
The_AirHawk's Avatar
Join Date: Jun 2007
Location: Leanin' Tower O' P-P-P-P-POWAAAAAAAAA!!!!
Posts: 11,491

You fill them "collapsed", without springs in them, or the cap on. Typically there will be a spec - "XX.Xml" or "YYYmm" for each bike. The easiest will be the "mm" to fill (this is the "air-gap") - as you just put oil in, pump the fork to get the air out of the slider, then mark a syringe/turkey-baster with that length, and "suck out" anything above the spec.

I would use only 10w fork oil to start with, most of those older bikes only had 8w-equivalent to begin with (many had "fish oil" - actually an additive to the mineral oil).

If you cannot find the correct capacity, I would start about 125mm down from the top (forks compressed). Decrease that number for "firmer" forks, decrease the oil-weight for "lighter" forks. Unless directed so by a manual, I would NOT go with less than a ~110mm air-gap.

I urge you to find the correct number, or seek advice from a company/individual that specializes in moto-suspension. I am only a lay-mechanic.
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...
The_AirHawk is offline   Reply With Quote
Old 09-25-2011, 01:26 PM   #3
Registered Member
Join Date: Sep 2011
Posts: 12

thanks ill have to talk to a local mechanic..
racefan is offline   Reply With Quote
Old 09-26-2011, 08:09 AM   #4
Founding Member
pushrod's Avatar
Join Date: Nov 2001
Location: Baja 'Bama
Posts: 3,642

I'd try to find the spec online.

Not many mechanics are going to know the spec on an 81 Honda.

They'll give you the same info Airhawk has...
You would not understand,
this is not how I am...

I have become -
Comfortably Numb.
pushrod is offline   Reply With Quote
Old 10-03-2011, 06:08 AM   #5
Registered Member
Join Date: Oct 2011
Posts: 3

I'd get a repair manual. Clymer's or similar.
thearcticsea is offline   Reply With Quote

Thread Tools

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off