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1999 321 Fork Cap Removal - Sag / Preload


totty79
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Hi,

It's been pointed out to me that my 321 has excessive sag on the forks just under the weight of the bike, I forgot to measure it before posting but it's in the region of 30 to 50mm. I suspect this is due to either missing preload spacers or very tired springs.

The previous owner said the forks had just been rebuilt - I wouldn't be at all surprised if whoever did them thought what are these bits of plastic pipe doing in here and threw them away.

I've stripped forks on a couple of older road bikes but I've never worked on forks with adjusters. Do the caps just screw off as normal or do the adjusters need to be disconnected somehow first?

There is a screw on the top surface of the fork cap and a small grub screw on the side, I'll upload some pictures.

20130616_192148.jpg

20130616_192203.jpg

Does anyone know the specs for the springs, particularly the free length. Also what are the spacer dimensions - ID, OD, length range.

Thanks

Allan

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Hi Allen,

You don't need to remove the adjusters, the caps unscrew as you'd expect. Remember to loosen the top triple clamp screws first. You will need to remove the large socket head bolts from the bottom of the fork legs (oil will drain out) to allow the spring cartridge to be withdrawn from the top.

I can't remember the free length but you may find one or both springs broken. Mine had one broken spring a while back and the two pieces had wound together making it much shorter.

Good luck with it.

Chris.

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Yea i don't know if it's a common fault but i had a busted spring in one of my fork legs,in my txt gasser ended up buying a pr of fork legs with a bent stantion just for the spring,think i may still have the other,so if u find it is the spring that's snapped,you can have it for price of postage.should be somewhere in my garage.Found the forks also have both plastic spacers

Edited by bilks
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those "caps" arent just caps. if you haven't found that out yet. the front forks are kind of a "cartridge" system. there is an Allen bolt on the bottom of the "tanks" by the axels, the top caps will come loose, but the whole thin (spring and all) comes out in one piece.

Find video version of the owners/mantenance manuals, by going to YOUTUBE.com, searching for the user called Gasgas.info this is the parts importer for USA, he and the BIKE IMPORTER for USA, made DVD's since gasgas didnt print manuals until what, 2008? or least maybe not english versions. Anyway Snell shows you how to take the forks apart, you will have to hunt a little for the older bike versions of vids maybe?

SPrings on those bike can "sack" out or break, not bad getting new ones. there are other ways of adding preload to the springs, by modding the existing plastic spacer. the way to disassemble the "cartridge" is a nut/bolt usually behind the little plastic spacer. Spacers can be made from PVC tubing/pipe. problem is I cannot recall what the "maximum length" the PVC can be, before you cause springs to bind up (compress until spring is totally collapsed, hitting bottom, aka becoming rigid, which is never good.

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  • 2 months later...

It's looking like I might finally get it fixed this week.

I couldn't source a new original or alternative spring. The used one bilks very kindly sent me unfortunately turned out to have a small crack, only really visible when compressed but I don't think it would have lasted long. I decided to have two made, the first two attempts were found to have defects in the wire - they're now making another pair which should be shipped this week.

Owned it since April, ridden it for 5 hours :-(

Parts availability is my number one priority for whatever bike I buy next. Although this one will be a half decent bike again before I'm finished with it.

It's been that long that I've now forgot how much oil each leg holds so I'll have to research that again.

Edited by totty79
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It's looking like I might finally get it fixed this week.

I couldn't source a new original or alternative spring. The used one bilks very kindly sent me unfortunately turned out to have a small crack, only really visible when compressed but I don't think it would have lasted long. I decided to have two made, the first two attempts were found to have defects in the wire - they're now making another pair which should be shipped this week.

Owned it since April, ridden it for 5 hours :-(

Parts availability is my number one priority for whatever bike I buy next. Although this one will be a half decent bike again before I'm finished with it.

It's been that long that I've now forgot how much oil each leg holds so I'll have to research that again.

Here's a simple tool to help with the top cap removal/re-installation. Each leg takes 300cc's of 5-weight fork oil.

Jon

ps. Almost forgot. That top cap only is tightened to barely snug. It's held tight by the upper tripleclamp and the oil seal is by the o-ring, not how tight you torque it down.

post-2532-0-83145600-1378155792_thumb.jpg

post-2532-0-75083800-1378155823_thumb.jpg

Edited by jse
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I've already got 7 weight oil, would a novice like me notice the difference?

Probably not, totty79. The viscosity index ratings given by manufacturers are sorta "vague", or more like a general guideline. One manufacturer's 5wt. is another manufacturer's 7.5 wt., or vice versa.... If possible, I'll try to find a somewhat techinical website, done by a man named Peter Verdonne, or something like that, which had a chart that was a good guidline for viscosity indexes of different brands of oils.

You will most likely be able to adjust out any differences you feel with your clickers (adjusters) or the oil level itself......

Jimmie

In EDIT: Here's that website with the chart of relative viscosity indexes. it gets pretty technical, but is a good reference of sorts. Scroll down to the bottom for the chart i mentioned above.....

http://www.peterverd...ve/lowspeed.htm

Edited by mr neutron
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Interesting link - I'll stick with the 7 that I've already got.

I'm yet to experiment with the clickers as they were overtightened and stuck when I bought the bike, I freed them off when I stripped the forks to check the springs. Hopefully they'll function correctly.

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  • 4 weeks later...
 

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