Fork Spring spacers - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 26 Old 10-12-2006, 01:55 AM Thread Starter
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Fork Spring spacers

Ok, I've heard about adding spacers to the fork springs, do you only do this with new progressive springs, or can you do this with the stock springs to stiffen them up a little, if you can, how big do you make them ?

2002 KLR 650
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post #2 of 26 Old 10-12-2006, 03:27 AM
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On the stock springs,I've seen them 1/2 " longer than the stock spacers.They used sch.40 cpvc.You replace the stock spacer with the cpvc.We did this with our dirt bike years ago and seemed to be ok.We also used a thicker oil and changed it frequently.

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post #3 of 26 Old 10-12-2006, 10:02 AM
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Longer spacers will preload the springs, making them effectively stiffer. They will also reduce the overall travel, since the longer spacer takes up that room.

The spacers on the progressive springs are shorter (as I recall), and the uncompressed springs are longer than stock. The overall uncompressed length is about the same. Here are the stock spring/spacer and the progressive spring/spacer for comparison.


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post #4 of 26 Old 10-12-2006, 01:23 PM
 
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If you really want to tune in the suspension for your needs. You can shorten your stock springs to increase the spring rate, then install longer spacers to provide the proper preload. This was posted on the old site, I don't have links but look for a coil spring calculator online. Deals with the # of coils, diameter of the coil, diameter of the wire used to form the coil. Our stock spring is somewhere around 28lbs per in. By reducing the number of coils the spring rate goes up. The calculator will help you determine where to cut. The longer spacer is required to keep the fork tube full.

The progressives are 28/40 meaning 28lbs in the initial travel, then become 40lbs when they compress. This is done by the coils compressing until they touch and effectively reduce the number of coils in the spring.

Very basic overview, hope it helps.

TW
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post #5 of 26 Old 10-12-2006, 11:40 PM Thread Starter
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Ok, all really great info. Though I can't really see how cutting the stock spring would increase the rate, even adding a longer spacer, isn't the stock spring a constant rate ? I think for the effort, I'll get a set of progressive springs. How much of a difference do they really make, is it something you would notice immediately ?or something you only notice with hard riding ? I've changed stock fork springs on my old RM 250, so it's an easy swap, but that was 30 years ago, and with stock replacement springs only.

2002 KLR 650
1978 RD 400 vintage racer
"I'm flat out like a lizard drinking"
Thanks Steve, you will be missed.
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post #6 of 26 Old 10-13-2006, 12:10 AM
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The stock spacers are 5.5" long. Throw in a 6" pvc spacer and see what you think. It'll only take 10 minutes of your time and a couple bucks for 3/4" sch40 or 80 pvc. I also think it's a must to go with heavier oil. I went with 20wt. The forks rebound way too quick with the stock stuff.
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post #7 of 26 Old 10-13-2006, 12:17 AM Thread Starter
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I'll try the cpvc spacer, I've got a couple hundred feet of sched 80 in my shop.

2002 KLR 650
1978 RD 400 vintage racer
"I'm flat out like a lizard drinking"
Thanks Steve, you will be missed.
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post #8 of 26 Old 10-13-2006, 07:59 AM
 
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Quote:
Originally Posted by gunny
Ok, all really great info. Though I can't really see how cutting the stock spring would increase the rate, even adding a longer spacer, isn't the stock spring a constant rate ? I think for the effort, I'll get a set of progressive springs. How much of a difference do they really make, is it something you would notice immediately ?or something you only notice with hard riding ? I've changed stock fork springs on my old RM 250, so it's an easy swap, but that was 30 years ago, and with stock replacement springs only.
Ah, Physics...The longer a spring is, at a constant coil, the softer it is. Here's a little demonstration you can do....

Take a ball point pen spring, compress it and feel the tension, now cut it in half and feel the tension of the shorter spring.
It's about double right?

TW
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post #9 of 26 Old 10-14-2006, 12:07 AM Thread Starter
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d'oh ! It's been a long week, I'm on pain killers until the doc can yank this tooth. I shoulda known that about the spring.

2002 KLR 650
1978 RD 400 vintage racer
"I'm flat out like a lizard drinking"
Thanks Steve, you will be missed.
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post #10 of 26 Old 10-21-2006, 09:37 PM Thread Starter
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well I did my fork springs today, changed the oil and added kynar spacers {instead of cpvc} I used 15w belray fork oil, I seem to recall the stock weight was 10 ? I know I mentioned it someplace else, but don't use cpvc if you can avoid it, cpvc doesn't like being saturated in oil, the stuff gets brittle, get some kynar, can't miss the stuff, it's red.

2002 KLR 650
1978 RD 400 vintage racer
"I'm flat out like a lizard drinking"
Thanks Steve, you will be missed.
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