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Old 09-23-2011, 05:46 PM   #1
racefan
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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
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Old 09-24-2011, 12:44 PM   #2
The_AirHawk
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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.
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Old 09-25-2011, 12:26 PM   #3
racefan
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thanks ill have to talk to a local mechanic..
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Old 09-26-2011, 07:09 AM   #4
pushrod
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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...
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Old 10-03-2011, 05:08 AM   #5
thearcticsea
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I'd get a repair manual. Clymer's or similar.
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