Front end spring and oil swap

Robert Reed

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So I'm working on swapping the springs and putting fresh oil in my forks, my front end is way too soft.

2 things came up that I'm curious about.

First of all, the old fork oil is bluish green. Is that normal? Not to worried about it but not what I expected to see.

Secondly, the springs I'm using are from the PO. He said he planned on doing it but never got around to doing it. He also stated that they were "progressive". I assume they came from Mike's. The weird thing is the old springs appear to be progressive as well because the tops coils are tighter than the rest. The new ones are slightly longer than the old ones though.

Am I wasting my time changing out the springs?

Old on left, new on right.
IMG_20180829_182159.jpg
IMG_20180829_182217.jpg
 
Im curiois about this myself. What year is your bike. That is usualy relevant. The later have some spring presure adjusment.
 
Yes, the original springs were a dual rate type. They give a nice ride but are just too soft overall. Yes, aftermarket replacements usually are longer. Measure the length of what you took out to see if maybe they have been replaced already. '78-on originals were about 482mm long.

rouFij7.jpg


Yes, fork oil is often colored like that. It's not brown like motor oil. The forks will work better if you use slightly more than the recommended just under 6 ounces of oil. Use 6.5 to 7 ounces per leg.
 
Im curiois about this myself. What year is your bike. That is usualy relevant. The later have some spring presure adjusment.
My bike is a 1980 and yes, it does have the top adjusters but I don't think they would have been sufficient enough to take up the sag I was dealing with.
 
Yes, the original springs were a dual rate type. They give a nice ride but are just too soft overall. Yes, aftermarket replacements usually are longer. Measure the length of what you took out to see if maybe they have been replaced already. '78-on originals were about 482mm long.

rouFij7.jpg


Yes, fork oil is often colored like that. It's not brown like motor oil. The forks will work better if you use slightly more than the recommended just under 6 ounces of oil. Use 6.5 to 7 ounces per leg.

5twins to the rescue again!

Old springs measure 19 1/16" on my tape measure which comes out to roughly to the 482 mm you mentioned.

Not sure if they've been replaced in the past but they were definitely assembled incorrectly. The spring in the right side fork leg was upside down!

New springs are about 19 1/4" so not a huge difference but I realize that's not the only factor at work here.

And yes, I planned on using your spec of 7 oz when adding the new oil.
 
So I'm working on swapping the springs and putting fresh oil in my forks, my front end is way too soft.
2 things came up that I'm curious about.
First of all, the old fork oil is bluish green. Is that normal? Not to worried about it but not what I expected to see.
Secondly, the springs I'm using are from the PO. He said he planned on doing it but never got around to doing it. He also stated that they were "progressive". I assume they came from Mike's. The weird thing is the old springs appear to be progressive as well because the tops coils are tighter than the rest. The new ones are slightly longer than the old ones though.
Am I wasting my time changing out the springs?
Old on left, new on right.View attachment 125112 View attachment 125113

Hi Robert,
yes, fork oil tends to be tinted. Not necessarily blueish green, I've seen some that was pink.
"Progressive" is the spring company's name. Neither of those springs are truly progressive,
A true progressively wound spring gets coil-bound one coil at a time to get stiffer as it closes.
Like 5twins sez, your springs are dual-rate. The spring keeps the same stiffness until the
close-wound coils touch each other then it has the same stiffer rate for the rest of it's stroke.
BTW a spring will work the same whichever way up it's fitted although having the heavier
close-wound end at the bottom will increase the front end's unsprung weight a tad.
To see if the new springs have a stiffer rate than the old ones you gotta test them.
Put each spring upright on a fork tube and put a big ol' cylindrical weight on top of it and
see how far down the weight will compress it.
 
This apparently happened after the XS650 era but when changing fork oil in newer Yamahas, the old oil stunk like dead fish. Asked around a bit and found that a fair amount of Japanese specialty lube was made at least partly with whale oil! There were some real issues when US banned anything containing whale oil and trannies designed to use it (a very effective lube) had to be reengineered!
I found replacement springs sold by bigtwin for 35mm Sportster forks are about 15% stiffer than the stockers and work well on the XS650.
Yes like Fred wisely sez The only way to know is test. I used my postal scale and a threaded rod contraption to compare length vs. force on a few sets of springs, it was a royal PITA to do.

I found WS2 (tungsten disulfide make a great fork seal lube, apply it before any oil touches the seal for best and longest lasting coverage. Did this to Madness in spring and the seals (pyramid parts brand) are amazingly effective. I haven't done it yet but will add some to fork oil next time I have one open.
 
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Yes, the original springs were a dual rate type. They give a nice ride but are just too soft overall. Yes, aftermarket replacements usually are longer. Measure the length of what you took out to see if maybe they have been replaced already. '78-on originals were about 482mm long.

rouFij7.jpg


Yes, fork oil is often colored like that. It's not brown like motor oil. The forks will work better if you use slightly more than the recommended just under 6 ounces of oil. Use 6.5 to 7 ounces per leg.
What is caster, trail? Dif in Canada?
 
I found replacement springs sold by bigtwin for 35mm Sportster forks are about 15% stiffer than the stockers and work well on the XS650.

Ggggary where did you buy the springs? I need to replace my old stockers and looking for something better.
 
Ggggary where did you buy the springs? I need to replace my old stockers and looking for something better.
Code Item Qty Price Grand Total
VTWIN24-0904 35mm Fork Tube Spring Set
1 $45.29 $45.29

Subtotal: $45.29
Tax: $0.00
Shipping Cost: $7.70
Grand Total: $52.99



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Can't go wrong with BelRay, their waterproof grease is great stuff too. 10W is a good viscosity with unmodified damper rods.
 
I continue to use 10W even with my Minton modded damper rods and it seems to work just fine. If your new springs also prove too soft, adding a 1" preload spacer could be a cheap fix. 1" is about the most you can go without risking the springs becoming coil bound under full compression, and anything less is rather pointless. An inch is about 25mm. The adjustable caps have 2 stiffer settings, each adding 10mm of preload for a total of 20mm more. A 1" spacer will start you out about a half step stiffer than what the caps alone will give you, and then you'll still have 2 stiffer steps after that if need be.
 
I started out with the vtwin springs on 77 no adjuster caps, moved up to adjustable caps was a bit of a handful getting those caps started. :rolleyes: I like them but cruiser type riders may find em too stiff. 7 oz. 15? weight with minton modded rods.
 
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I continue to use 10W even with my Minton modded damper rods and it seems to work just fine. If your new springs also prove too soft, adding a 1" preload spacer could be a cheap fix. 1" is about the most you can go without risking the springs becoming coil bound under full compression, and anything less is rather pointless. An inch is about 25mm. The adjustable caps have 2 stiffer settings, each adding 10mm of preload for a total of 20mm more. A 1" spacer will start you out about a half step stiffer than what the caps alone will give you, and then you'll still have 2 stiffer steps after that if need be.

I'm going to see what it feels like with 7oz and the adjusters on the softest setting and bump it up from there if need be. I haven't put it back together yet as I want to get some stainless screws for the drain ports. I though I had some but can't seem to locate them.

Before doing the swap the front end would drop so much just from taking it off the side stand that the commando boots would bind on themselves, I would imagine it can only get better.
 
The new springs should help but the extra oil contributes quite a bit as well. These forks just plain work better with a bit more oil in them. The resulting higher oil level means less air space above it and that gives more of an "air spring" effect, kinda like air forks. It really helps reduce the amount and severity of fork dive during braking. And the Minton mods make for a smoother ride over all the little bumps. The forks will now better respond to and soak them up rather than transmit them through to you.
 
I have a machine shop here at work that has almost every nut, bolt, screw, etc that you can imagine yet we don't have anything in M4x8. Everything is either M4x6 or M4x10.

Think I would have any luck at Lowe's or Home Depot? Checked the Ace hardware and struck out.
 
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I never even tried finding them locally, I just ordered a big bagful from McMaster-Carr. If you have no luck finding them, I have way more than I'll ever need so P.M. me and I'll send you some. It's something you can change out any time, just lean the bike way over and little, if any oil will leak out as you do the change.
 
What is caster, trail? Dif in Canada?

Hi joebgd,
Clymer's sez 27º & 115mm (presumably for US models) and don't even mention those alternative caster & trail numbers.
Canada got US models with MPH/KPH dual reading speedos, Kilometer Odometers & relaxed EPA strangulation.
BTW are you asking why the different numbers for different marketing zones or are you asking what those numbers mean?
 
I never even tried finding them locally, I just ordered a big bagful from McMaster-Carr. If you have no luck finding them, I have way more than I'll ever need so P.M. me and I'll send you some. It's something you can change out any time, just lean the bike way over and little, if any oil will leak out as you do the change.

Put it back together with the original drain plug screws. Definitely feels better already but I may use the adjusters to stiffen it up even aabit more.
 
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