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Defeating fork air system?
- polkat
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05 Nov 2009 15:49 #331678
by polkat
Defeating fork air system? was created by polkat
I have another KZ (KZ650) that I rarely post about, as it is in good shape. But I have had problems with the air/oil forks. Even though the seals are good and don't leak, they are usually out of air on one or both sides when I check it. Others I have talked to say that the air/oil system that apparently many manufacturers went to in the early 80's is a poor design, and I have heard of some who defeated the system by adding a spacer above the spring and not using air at all.
Has anyone here done this, did it work, and what length of spacer did you use?
Has anyone here done this, did it work, and what length of spacer did you use?
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- saltydog
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06 Nov 2009 15:23 #331827
by saltydog
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
Replied by saltydog on topic Defeating fork air system?
I got tired of messing with the air on my 81 KZ1000 CSR, Wouldn't hold two days. Forks would bottom out on a hard bump. I put a pvc pipe spacer, I believe it was 2 inches long, on top of my springs. I was gonna buy some Progressive replacement springs, but the spacer works so well, I don't need them.
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
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- polkat
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06 Nov 2009 19:06 #331874
by polkat
Replied by polkat on topic Defeating fork air system?
I can pretty easily start my fork caps into the threads with the stock setup and the forks fully extended, and they get tight about half way down. I'm wondering if I'd have trouble getting the caps in with a 2" extension?
I don't really know if my present springs are stock (there are no markings), but the coils get wider at one end. Maybe that's stock and not prograssive.
Yea, I loose the air in about the same time, although the seals (just new) don't leak. New or not, I suspect that is where the air is getting out. If I can get the caps back in, I might try the spacer idea.
I don't really know if my present springs are stock (there are no markings), but the coils get wider at one end. Maybe that's stock and not prograssive.
Yea, I loose the air in about the same time, although the seals (just new) don't leak. New or not, I suspect that is where the air is getting out. If I can get the caps back in, I might try the spacer idea.
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- saltydog
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07 Nov 2009 03:47 #331909
by saltydog
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
Replied by saltydog on topic Defeating fork air system?
"Progressive" is a brand.
www.progressivesuspension.com/
I guess all of the stock springs are progressive in type of spring
In some of the "Progressive" applications, they come with instructions on how to calculate spacer length which is on their website.
Mine is probably longer than necessary, but I figured if a little would do a little bit of good then a lot would do a whole lot of good. Too much would be just right.
I remember having a little bit of a struggle getting the caps back on
I guess all of the stock springs are progressive in type of spring
In some of the "Progressive" applications, they come with instructions on how to calculate spacer length which is on their website.
Mine is probably longer than necessary, but I figured if a little would do a little bit of good then a lot would do a whole lot of good. Too much would be just right.
I remember having a little bit of a struggle getting the caps back on
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
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- ready2ryde1985
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- got to love these kzs
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31 Jul 2010 20:01 #387341
by ready2ryde1985
84 kz 700 a1
82 kz550 ltd
Replied by ready2ryde1985 on topic Defeating fork air system?
What size pvc pipe was used as a spacer I would like to do this befor I head to sturgis.
I bought 2 1/2 inch cuplings they look like they will fit ?.
and they are thicker than a single piece of pvc.
Thanks in advance for the info :woohoo:
I bought 2 1/2 inch cuplings they look like they will fit ?.
and they are thicker than a single piece of pvc.
Thanks in advance for the info :woohoo:
84 kz 700 a1
82 kz550 ltd
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- polkat
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31 Jul 2010 21:43 #387349
by polkat
Replied by polkat on topic Defeating fork air system?
This topic was started a while ago. Since then I got a response on another forum (I think) that said to use old 750-4 valve springs (both the inner and outer) on each side above the stock washer.
Interesting! Anyone ever try this?
Interesting! Anyone ever try this?
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- saltydog
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01 Aug 2010 00:15 #387360
by saltydog
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
Replied by saltydog on topic Defeating fork air system?
I used some 1" that I had laying around.
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
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- ready2ryde1985
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01 Aug 2010 07:21 #387382
by ready2ryde1985
84 kz 700 a1
82 kz550 ltd
Replied by ready2ryde1985 on topic Defeating fork air system?
Thanks for the info !!!
I hope this helps my forks are way to soft !!!
If I had the left over springs I would try that method
One more Question .
So I pull the screw at the bottom drain the oil then pull the fork cap . // Right
Then cram the piece of pvc in and put the cap back on .
OO and add oil. :S
I hope this helps my forks are way to soft !!!
If I had the left over springs I would try that method
One more Question .
So I pull the screw at the bottom drain the oil then pull the fork cap . // Right
Then cram the piece of pvc in and put the cap back on .
OO and add oil. :S
84 kz 700 a1
82 kz550 ltd
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- saltydog
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01 Aug 2010 07:27 #387387
by saltydog
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
Replied by saltydog on topic Defeating fork air system?
No need to drain unless changing oil. Be sure to relieve the air pressure.
1981 KZ1000 CSR, 1982 KZ440 ltd, 1972 Honda ct90, 1978 KZ 650
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- mjg15
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01 Aug 2010 10:36 - 01 Aug 2010 10:41 #387418
by mjg15
'80 Z750fx
'81 KZ550A
'81 GPz550's, Too many!
'82 KZ1000R
'82 GPz750
'90 ZR550
Project photo album: s163.photobucket.com/albums/t289/mg15_ph...GPz-ZR550%20project/
s163.photobucket.com/albums/t289/mg15_ph...current=DSC01286.jpg
Replied by mjg15 on topic Defeating fork air system?
Keep in mind that adding a spacer above your spring, which increases the preload, is not exactly the same thing as adding air. The spacer only increases the preload, thereby reducing sag when bike is loaded. Adding air increases the preload and effectively increases the spring rate throughout the entire fork travel. It also has a progessive nature , as the effective rate will increase as the air chamber volume decreases (fork compression.
FWIW, the stock springs in the air fork equipped bikes are typically 50%-60% of the spring rate of what a proper non air fork bike would require. My 550 comes with .490 kg/mm springs, but the reccommended rate is .950 kg/mm
FWIW, the stock springs in the air fork equipped bikes are typically 50%-60% of the spring rate of what a proper non air fork bike would require. My 550 comes with .490 kg/mm springs, but the reccommended rate is .950 kg/mm
'80 Z750fx
'81 KZ550A
'81 GPz550's, Too many!
'82 KZ1000R
'82 GPz750
'90 ZR550
Project photo album: s163.photobucket.com/albums/t289/mg15_ph...GPz-ZR550%20project/
s163.photobucket.com/albums/t289/mg15_ph...current=DSC01286.jpg
Last edit: 01 Aug 2010 10:41 by mjg15.
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- PLUMMEN
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01 Aug 2010 10:39 #387420
by PLUMMEN
Still recovering,some days are better than others.
Replied by PLUMMEN on topic Defeating fork air system?
have you checked the shrader valves/valve cores?
Still recovering,some days are better than others.
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