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Old 05-23-2009, 06:01 AM   #1
trojwl
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Question 2002 Vmax Fork Problem

My forks will not maintain pressure. Not sure if it is one or both sides. The fork tubes externally are absolutely dry (no leaks there). However, they do lose pressure rather quickly and there is usually a very small amount of oil under the right side cap over the shrader valve. This tells me that there may not be a problem with the seals and it may just be a defective shrader valve.

If the oil and air are "mixed" together inside the fork, my shrader valve theory would make some sense.

Also, this causes oscillation in the forks as if there was an imbalance in air pressure between the forks.

Also, are these your ordinary run-of-the-mill shrader valves that are available from NAPA?

Can someone please discuss? thanks
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Old 05-23-2009, 06:12 AM   #2
MOKE1K
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When did you last service them? The shrader valves should be pretty standard.
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Old 05-23-2009, 06:31 AM   #3
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Easy to check. Remove shrader valve. Compare to new shrader valve from auto supply store. If different order new one from Yammerhammer.
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Old 05-23-2009, 07:13 AM   #4
trojwl
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The forks were "serviced" at Yamaha dealer. I had a high speed wobble (over 60 mph) a couple years ago. I asked them to look at the forks. The problem they said was a loose fork retainer nut (the big one in center of assembly) which they tightened. It fixed the problem. Not sure how closely they inspected the forks.

The bike has less than 12,000 pampered miles and is kept covered in garage. Given the typically high quality of Yamaha machinery, I would not expect to require any fork "servicing" for many more miles.

I will check the shrader valve and compare against a new one from NAPA.

Again, thanks for the replies.

Any more thoughts are always welcome.

VMAX's ROCK!!!
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Old 05-23-2009, 07:39 AM   #5
mscuddy
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Air assisted forks are so 1980's. I had the same setup on an '82 KZ750 that would cause the forks to collapse at freeway speeds, throwing the bike into a wobble when the brakes were applied. Dangerous.

You can dump the air assisited system and go with Progressive Suspension fork springs engineered just for that purpose, i.e. getting rid of the air assist.

Just one more thing to worry about (air phorks). You'll be surprised how much better the bike handles too.
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Old 05-23-2009, 08:56 AM   #6
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Things that have seals in them eventually leak no matter what you do.
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Old 05-23-2009, 09:01 AM   #7
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I'm with cuddy on this one - typically, riders run with too-much air pressure, and the forks start leaking sooner that a "normal" fork, but with the added annoyance of losing preload-pressure. Ditch the pressure-assist.

If it's losing pressure - it's losing pressure. Air-entrainment in the oil will just result in foamy oil - the pressure in the fork will remain unchanged (ruling-out any changes due to rising temperature or outgassing of the oil - which would INCREASE pressure).
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Old 05-23-2009, 12:26 PM   #8
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I am extremely careful when adding air. Actually I use a small portable tank and fill it up to 8 - 10 psig and the administer from tank. That way it is literally imposible to overpressurize.
Like I said the forks are totally dry. I don't see how it could be the fork seals. You would see some evidence of oil on the tubes.
Am I missing something here?
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Old 05-23-2009, 08:59 PM   #9
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When I say forks are dry, I don't mean there's no oil. I mean the fork tubes externally above the seals have no oil film on them at all.
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Old 05-24-2009, 02:08 PM   #10
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The "air" forks suck. Call Traxxion Dynamics in Woldstock GA. Get the replacement "oil" cartridges. You'll be much happier.
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