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Changed fork seals, fork bleeding question..

  • Thread starter Thread starter Natron037
  • Start date Start date
N

Natron037

Guest
I put new seals in the gs650 forks I bought for my bike. I followed the instructions on here to set the fluid level (compressed fork w/ no spring, set up a "sucker" at the correct depth, poured some fluid in and pumped them, pour in more fluid and pump them, keep filling and pumping until it is near where it has to be then suck out to correct level). Here's the problem.. while I was filling and pumping I noticed that the only real resistance is at the very top and very bottom of the stroke. Does that mean there is still air in there? Should I worry about it? Is my fluid level wrong? I left the forks sit for a half hour compressed with the fluid level about 4" from the top in hopes any air would work out. I also pumped them for about 15 min straight and no change. They are air forks, so would air pressure change anything? I am worried they might not be working correctly. Any ideas?
Thanks
Nate
 
What fluid did you use? Heavier fork oils will provide more resistance, but it is not unusual to have more resistance toward the end of travel. This helps prevent topping or bottoming.

The fact that they are air forks only means that air is added as an additional spring, and does not really mean anything in regards to damping.

.
 
I used Bel-Ray 15w fork oil. It seems like there is almost no resistance in the middle. Granted I wasn't pumping it fast, but I still think there should be some drag as I'm pulling it through it's stroke.
 
Natron037 said:
I used Bel-Ray 15w fork oil. It seems like there is almost no resistance in the middle. Granted I wasn't pumping it fast, but I still think there should be some drag as I'm pulling it through it's stroke.
Click to expand...

Nah, sounds OK. At the speeds you are moving it, there will be almost no resistance. Make sure you worked the air out, which it sounds like you did OK, set the level and button them up. Damper rod forks don't have a lot of places to trap air like the current generation of twin chamber MX forks (now those are a PITA to pull apart and rebuild), just stroking them a few times should be more than enough.

Mark
 
Having the forks back on the bike.. I am starting to think I did something wrong. I could bottom the forks just by pushing down on the bars. I made 1.125" spacers and have about 3/4" static sag and about 2" of sag with me on the bike (I can still bottom the bike if I bounce on the bars). I need to make longer spacers I believe, although I have no idea how I am going to get the caps started.. it was hard enough with the 1.125" spacers! I did put about 7lbs of air in each fork and that made it stiffer. If I have to take the spacers out and put 1.5" spacers in how much more oil should I add? I would rather it on the stiff side. How much makes a difference.. 10cc or 100cc? I originally set the level at 140mm from top with forks compressed and no springs in them. The tubes are a little over an inch inside diameter so 10cc would raise the level to 120mm give or take.. if my math is correct. I don't like putting air in forks and I may put different fork caps on it. The forks are from a 650G and there is no anti-dive.. just regular forks with oem air caps on the top. Thanks!
Nathan
 
Do NOT add more fork oil.

Never go above the 140mm level (measured with springs out and forks collapsed all the way) or you run the risk of hydro-locking when the forks compress all the way.
 
If you can bottom the forks the springs are sacked out. replace them with progressively wound units.
Spacers only mask the problem. You will still bottom out, only sooner. The springs will be compressed more than the damper rod.

Then you can experiment with the oil as to how it reacts . Oil is for dampening (controlling) the movements, the spring actually supports the bike.

Or you could install cartridge emulators.
 
Just a question, what were they like before you stripped them. If they were the same could they have been tampered with before? Have you measured the length of your springs and compared to the service manual? Are the bushes in a good condition? Do you have all the parts in there?
Some people are cutting springs, using custom fork oil mixtures, adding spacers and other type of mods and maybe the problem is not due to wear but something else. Were there any spacers in before or have you added those now to try and solve the problem?
I have my GS1000GT apart at the moment and if they are similar I will gladly do any comparisons for you, but I am not sure if they are the same. I have some photos and have made up a small howto, just waiting for my seals to arrive and will then complete.
Apologies for the stupid questions, but we have to see some pictures or have enough detail to try and give you a more definite reply if possible..
 
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bwringer said:
Do NOT add more fork oil.

Never go above the 140mm level (measured with springs out and forks collapsed all the way) or you run the risk of hydro-locking when the forks compress all the way.
Click to expand...

Thanks for this tip, I was wondering about this myself.
 
Well.. I have the stock 550L forks still. The main "long" spring is the same length, the top "short" spring was longer on the "L". I may take the long springs out, compare wire dia, active coils, ect.. then swap them and see if it makes a difference. The short spring on the top is wound tigher than the bottom one so it should be the "soft" spring, correct? With the spacers out, (stock springs) the cap is about 1/2" from threads engaging, is that normal?
 
Your forks sound different to mine. I have attached a picture of them. Mine has the main spring, close wound to the top, a spring cup, a spacer 77mm, then the top nut cap. The top nut cap touches the spacer when it is partially screwed in. Inside the inner tube there is a damper with a bush and a short spring.
 
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That fork looks identical to mine, even the top cap. So in your forks there is no "short" spring on the top, just a solid spacer? When I look at the fiche for an 81 650g there is a short spring but for an 81 850g there is just a spacer. Maybe just a spacer is the cure to my problems.
 
Natron037 said:
That fork looks identical to mine, even the top cap. So in your forks there is no "short" spring on the top, just a solid spacer? When I look at the fiche for an 81 650g there is a short spring but for an 81 850g there is just a spacer. Maybe just a spacer is the cure to my problems.
Click to expand...

Definitely only the spacer on top for the GS1000G and GS850G. The spring is 421 mm long and must not be shorter than 416 mm according to the manual. Someone must have done some modification to yours that did not work. The spacer is just a rolled bit of flat metal and you can easily make them up if you cannot get any I think.
 
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I'll check the spring length and compare. 650G forks did have a small spring up top, 850's and 1000's did not.. according to the fiche. does anyone have a set of 850 or 1000 forks handy that they could measure the length of the top spacer for me?
Thanks
Nate
 
Natron037 said:
I'll check the spring length and compare. 650G forks did have a small spring up top, 850's and 1000's did not.. according to the fiche. does anyone have a set of 850 or 1000 forks handy that they could measure the length of the top spacer for me?
Thanks
Nate
Click to expand...

Nate,
Mine is out at the moment and measures 77mm x 27mm.
 
Natron037 said:
I did put about 7lbs of air in each fork and that made it stiffer.
Nathan
Click to expand...

They came from the factory with 7psi but you can go as high as 11max. But sounds like the group has led you to having the wrong springs in there.
 
UPDATE!! I got the bike back on the road last night and the forks feel fine if not a little stiff with the 1" spacers I put in and fluid level set to 140mm. They did feel really mushy sitting still and I was worried about bottoming out under hard braking but everything is perfect. Thanks for all the help guys!
Nathan
 
Glad you got it sorted out. You can even play around with the oil weights now 5W to 20W as well as the airpressure.
 
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