forks losing air immediately ('83 vt500ft ascot)
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  1. #1
    jml
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    forks losing air immediately ('83 vt500ft ascot)

    I replaced the oil seals on the forks on my '83 Ascot, and when I went to put air in them they lost it almost immediately (like 20-0 in well under a minute). I don't see any leaks and everything is torqued properly, is there some trick I should do after reassembling them to keep them holding air?

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    Senior Member Rscottp's Avatar
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    My CX500 had air forks and the recommended pressure is 10-16lbs. The FSM also says to inflate with a hand pump only so as not to damage anything. I'm guessing you overfilled them and cause an air leak someplace.
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    Supporting Member crazypj's Avatar
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    How are you trying to check pressure? Thew volume is so small it isn't possible to check with a normal tyre gauge. Cheapest option would probably be a bicycle air fork pump. It screws onto valve and has gauge with a 'lock' so you don't lose pressure removing it. You could also look for a factory special tool but they were incredibly expensive new and pretty rare used. Someone must make a replacement, you need to have a gauge and airtight valves. Oh, just rememberd something. Do you have a cross link air tube at top of forks? If so, to seals in that may be damaged or just hard from old age. If the 'link' is drilled through top or bottom yoke, you ma not have things lined up properly? Unfortunately I haven't worked on one since 1983 so just can't remember
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  5. #4
    jml
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    Quote Originally Posted by crazypj View Post
    How are you trying to check pressure? Thew volume is so small it isn't possible to check with a normal tyre gauge. Cheapest option would probably be a bicycle air fork pump. It screws onto valve and has gauge with a 'lock' so you don't lose pressure removing it. You could also look for a factory special tool but they were incredibly expensive new and pretty rare used. Someone must make a replacement, you need to have a gauge and airtight valves. Oh, just rememberd something. Do you have a cross link air tube at top of forks? If so, to seals in that may be damaged or just hard from old age. If the 'link' is drilled through top or bottom yoke, you ma not have things lined up properly? Unfortunately I haven't worked on one since 1983 so just can't remember
    Y'know, I was wondering if I was letting all the air out just by checking it. I have a small hand pump like you're talking about that I was using to pump them, but the scale is so skewed that it's hard to get an accurate reading, so I was using a car gauge to check after. I'll try my floor pump and see if it works any better.

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    Supporting Member crazypj's Avatar
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    Really you need an adapter with a shut off valve plus an accurate dial type gauge. Something I have seen on MX bikes (way back when) was a water bottle used as an air reservoir with high pressure ines connected to fork air valves. I'll see if I can find a picture of the Suzuki factory air setting tool, it's the best one, even Honda dealers bought it in preference to the Honda version. Looks simple enough to make from some plumbing and air line parts. Or, you could get one of these
    https://www.ebay.com/itm/Gauge-Pump-...HCap6UEMtMWMsA
    Last edited by crazypj; 10-02-2019 at 06:12 PM.
    There are three types of people in the world, those who can count and those who can't
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    Senior Member Twowheelrich's Avatar
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    You need something like this. I have two identical to this model (but branded differently) - one has a high pressure gauge(0-300psi) and the other has a low pressure gauge (0-50psi). They both have worked perfectly with all my air and air assisted motorcycle and mountain bike suspension units for the past 20+ years, but the lower pressure gauge is easier to read/dial in pressures with. Both have a small button to bleed off excessive pressure. I had to replace the gauge once (dropped it on pavement) with one from Mcmaster-Carr. Bomb proof and totally reliable and serviceable.

    https://www.ebay.com/itm/High-Pressu...gAAOSwV05dYY5z
    Last edited by Twowheelrich; 10-02-2019 at 06:20 PM.
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    Supporting Member crazypj's Avatar
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    Yep, that would be even better for not a lot more cash. You could always send seller a message and make an offer around $15.75. As long as it's above starting price it's usually accepted
    There are three types of people in the world, those who can count and those who can't
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    Senior Member Twowheelrich's Avatar
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    I think I paid more for mine 20 years ago than what that one is selling for now lol. Also, I had to go look but my low pressure gauge reads 0-60psi (not 0-50) but the gauge can be swapped out easily enough, and cheaply. You might find it tough to dial in 25 psi, for example, with a higher pressure gauge. I couldn't. I can't remember the last time I used the higher pressure pump, but it was with Rock Shox Duke Race, back in the day. Even my Kawa Councours didn't require much psi, but adding or removing just a few psi made a noticeable difference, especially in the front.
    1973 CB 450 - Sold!
    1968 CL 175- up on blocks
    1991 KLR 250- 'Ol reliable
    2005 Suzuki Wee-Strom - just got it!

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    Supporting Member crazypj's Avatar
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    I rode mountain bikes 25+ years ago and remember the air shock 'revolution'
    Pumps for forks and shocks were some crazy prices when they first appeared, at least double what they are today but often way more than double for a 'name brand'
    There are three types of people in the world, those who can count and those who can't
    I'm not a complete idiot, but, I'm working on it

  11. #10
    Senior Member Twowheelrich's Avatar
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    Upon re-reading the original post, I would suggest diving back in and looking for some foreign matter that might be causing the air leak and look closely at the new seals- oil seals may not necessarily be effective air/pressure seals. On your way out, give everything a light coating of oil or grease and then add the preferred volume of oil. Before adding air pressure, pump the heck out of each fork leg right side up and it doesn't hurt to turn it upside down as well initially to make sure the oil goes everywhere it's needed.

    Also, nearly every air spring and air assisted spring setup I've worked on in the past 20 years relies mainly on o-rings and some type of lube to maintain pressure and not just lip seals, including the pumps I use and recommend. As an example, my favorite mtn. bike fork (since my 'fleet' of mtn. bikes is all 'vintage') is my Noleen (K2) with an air spring/air damping system. They require occasional injections of grease and annual service but the lip seals keep the dirt out of the workings and just a couple of o rings keep the air pressure in, even after 18 years! 32mm stanchions(low flex), light weight, stupid simple maintenance works for me!
    1973 CB 450 - Sold!
    1968 CL 175- up on blocks
    1991 KLR 250- 'Ol reliable
    2005 Suzuki Wee-Strom - just got it!

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