Error Error!!! Fork spring free length

Scottrt

Scottrt

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In regards to the 80s bikes with the adjustable Pre-loader cap...The official Yamaha service manual and the Clymer manual Put the spring free length at 610 mm or 24 inches. Everything I've read here and People quoting the Haynes manual generally say 482 mm. .... Which seems correct to me. I just want to confirm that 610 is definitely wrong Before I place my order for some race tech springs (Higher rate, But hopefully OEM length)
 
Just went to the barn and pulled cap and spring from a salvage '82 model fork. 610 is an error, 482 is correct. Keep in mind that if you're ordering straight rate springs to use with cartridge emulators they'll be shorter than OE, and you'll need to cut spacers.
 
Wow, thanks for going to such effort. Indeed, the RaceTech single rate springs are 23.5 x 410mm, so I will need to fab a nearly 3 inch spacer. I am curious as to why they make the spring shorter, and does the use of a spacer reduce total travel?
 
They are producing a spring that works for more than one model of bike. That won't change your travel. I put the spring in first then a washer that is a close fit to the tube, spacer on top of the washer. I usually use PVC pipe for a spacer cut to a length that still lets me screw on the cap. I like to be just able to push the spring in and put the cap on. Has always worked good for me. Not sure what PVC diameter to use for your forks, 1/16" to 1/8" smaller than your tube would be right. I have turned down the dia. before.
 
They are spec'ing a mere 15 mm of preload and I plan on reusing my adjustable top caps, so I'll have to figure out what I need once I'm able to put everything back together and measure my relationships. Three-quarter inch schedule 80 PVC probably will work great.
 
For one thing, half of the spring weight is unsprung weight, so performance springs are made as light possible. The spacer probably won't reduce travel. If you want to be sure, measure the wire diameter carefully, multiply it by the number of coils in the spring, and add estimated preload (spacer plus cap). Then subtract that number from the free length of the spring. The result is fork travel before coil bind.

And right, washers above and below the spacers. If in doubt cut the spacers a bit overlength so that you can be sure that they're not too short to yield the desired sag.
 
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You can always cut spacers of different lengths, say 1/4 inch increments, then start with a 2.75 inch. Check sag If not enough try a 3 inch , check sag. ect, till you find the length you need.
You say you want to use the adjustable caps, I might start my testing with the cap in the center position. Adjust the spacer to get the sag you want. I found about 25 mm to be good. Once set you this way you can loosen the adjuster for a plusher ride or tighten for a firmer ride.
I replaced my springs with a set of straight rate springs for older Harley's The XL and FX's from the mid to late 70's. used a 35 mm fork. These springs are very close to the XS spring but longer. I have the specs somewhere just can't put my hands on them now.
When the fork is assembled the spring come up about even with the top of the fork. Bit tricky to get the adjustable caps on. Once on I get about 25 mm sag on the lowest setting. About 12 on the middle and can't get to the highest setting.
The lowest setting is firm, the middle setting is a bit harsh.
I would be nice if I could change the spring length so I could get the 25 mm sag on the middle setting. That way I could have a bit more options on ride firmness.
When I just want to cruise around I could set them softer or for more aggressive ring I could turn them up. When I load the bike up for a trip having the firmer setting helps with the extra load.
I remember as a kid some of the older folks talked about lowering their cars by setting block under the cars bumpers at te height they wanted them and then using a torch the heat the coil springs to red hot. This let the spring bend enough to shorten the spring so the car rode lower.
I have thought about using a long piece of all thread rod to put through my spring with nuts to compress the spring to about the same length as stock springs. Then heating like those old guys did to get them shorter.
I'm afraid I'd ruin my springs. I know just cutting them off won't work, that would make them stronger. This isn't what I need.
I know there are places that can make springs to order. I'm retired now sop my income is a bit tighter, Playing with these springs is a cheaper way to go.
Is this heating and reshaping springs something that will cause them to break or go weak? I don't recall what or if the old guys said anything about that.
Leo
 
Heating the springs most likely would require you to re-temper/re-harden them afterwards. Unless cooling off in ambient air is sufficient to do just that. Sounds a bit dodgy to me. You may be better off getting some springs that are a bit on the soft side, cut off a gew coils, and compensate with longer spacers. Just check for coil bind.
 
Trust the guy that tried tempering leaf springs he heated and bent LOL if you bend just let them slowly air cool. Do not try to temper they will get so brittle they may shatter.
Trick that works; use a set of caps from a 34mm fork they are plug and play, aluminum, and shorter than the 77 35mm caps. What I did on restomod and maybe others. But they are NOT adjustable.
 
You can "sack" your springs a bit by putting them on all-thread and tightening them down until they're coil-bound .....

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I inadvertently discovered this while measuring some to determine how much of a preload spacer I could safely add. I know, you can count the coils, measure the spring wire diameter, and do some math, but it didn't ever match my actual measurements.
 
Scottrt said:
Wow, thanks for going to such effort. Indeed, the RaceTech single rate springs are 23.5 x 410mm, so I will need to fab a nearly 3 inch spacer. I am curious as to why they make the spring shorter, and does the use of a spacer reduce total travel?
Click to expand...

I bought some aluminum pipe and fender washers. I think I nailed the laden sag in the first try. My springs came from Traxxion Dynamics. It really ended up being a straight forward job.
 
Old thread revival. I’m rejuvenating my XS650SK forks. The manual threw me the curve ball again. One spring is 480 mm. The other is 475 mm. Disassembling old forks isn’t what I had in mind for today.
 
Another error! The Factory Service Manual says 44.5 ft lbs for the bolt going into the damper rod. I believe that should be 14.5 ft lbs.
 
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Sounds like your springs have sacked a little, one slightly more than the other. If you plan on continuing to use them, they can be "fixed" by adding some short preload spacers. Personally, I like the stock springs. They are a two-way progressive spring and give a nice ride, but they always seem to be a little too soft, even with the adjuster cap full on. Each step on the adjuster adds 10mm of preload, for a total of 20mm available. So, I figured if I could add a little more than that with a spacer, that might do the trick. I installed 1" spacers (about 25mm) but that proved to be a bit much. I think that was because I didn't take into account the thickness of the washer I added too. That added another few MM to my preload, making it 27 or 28mm, close to another full step on the adjuster (if it had one). So, I pulled the spacers and shortened them to 13/16". Now, including the added washer, I've got 23 or 24mm of additional preload, and that seems good.
 
5twins said:
Sounds like your springs have sacked a little, one slightly more than the other. If you plan on continuing to use them, they can be "fixed" by adding some short preload spacers. Personally, I like the stock springs. They are a two-way progressive spring and give a nice ride, but they always seem to be a little too soft, even with the adjuster cap full on. Each step on the adjuster adds 10mm of preload, for a total of 20mm available. So, I figured if I could add a little more than that with a spacer, that might do the trick. I installed 1" spacers (about 25mm) but that proved to be a bit much. I think that was because I didn't take into account the thickness of the washer I added too. That added another few MM to my preload, making it 27 or 28mm, close to another full step on the adjuster (if it had one). So, I pulled the spacers and shortened them to 13/16". Now, including the added washer, I've got 23 or 24mm of additional preload, and that seems good.
Click to expand...
Thanks. I just opened up some old rusty forks in my stash. The springs are 482 mm. I like them just fine on these Mississippi roads and I run them without preload. The oil level is set to 130 mm from the top with the fork collapsed and the spring out.
image.jpg

I sure have made a mess!
 

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