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Discussion Starter #1 (Edited)
Showa front fork legs, early 916 40mm mounting holes on 900ss

Hi guys

So, before going all in on Maybe bying my first duc, i wondered, are these forks a direct swap on the 900ss carb models?

I have a set of beefy calipers With 40mm mounting holes, (i Would want to use on my duc)so I Would want to keep that on the bike.

And if so, is These forks a upgrade on the old duc 900?

Hope it makes sense :)
 

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no. all the sbk showa forks 916 (94) onward are 53mm outer diameter at both upper and lower triple clamps. well, pre pani anyway.

all the 41 and 43mm showa upside down forks used 91 - 10 (ish on later ones maybe on some) in non sbk models - ss, m, st, sc/gt are 50mm upper triple and 54mm lower.

if you got some 43mm showa forks from ssie, st, m, etc you can use those outers and put the sbk inner tubes and bits into them. the 65mm caliper spacing started with 98 sbk models (and 97 st2), so any 748/916 forks 94 - 97 will work for that. i think the sbk cartridges will have more travel than the other forks.

or you can get an upper triple with 53mm holes or bore the originals to 53mm and shim the lower with a 0.5mm shim to take up the 1mm difference.
 

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The forks will fit with modification, you need to bore the top clamp and shim the lower.

If caliper mounts are the same then they bolt right up as will a later style wheel from a injected supersport,916,st series or monster with a 25mm axle and 6 bolt rotors. You will need a new speedo drive to match. Also remember your clip ons will need to be changed.

Changing uppers to fit is another option.

Reason to make the swap?
1. tell all your friends you have "superbike forks"
2. better oem valving
3. Better low speed metering circuit
4. straight rate springs
5. 43mm tubes flex less

Reasons to not make the swap?
1. cost to swap all parts needed
2. modifying a top tree by boring it. - you used to be able to buy a aftermarket tree to fit them (speedymoto or cyclecat).
3. Showa 41mm forks can be made to work well enough for most internally and are period correct.
4. Springs will be .95-1.0 and on a light bike like the supersport you will need to be 250-275lbs to make the springs work.

Watch for the cascade of modifications and parts needed and compare that to the cost to fix what you have. Have a honest talk with yourself (done best with a mirror after a few drinks)about whether you want the look, better suspension or are you replacing bad forks now. Do you plan to race ? is it a custom? do you want to keep it close to original (best value later in life) or simply make the bike the best hot rod you can (resto-mod)?

I have compared fixing oem
superbike and gsxr 1000 fork swap and there are pluses and minuses to all of them based on both performance and cost. none of them are as cheap as we want and all cost good money but the added costs of the conversions surprise many people. I have done them all and would say the decision is mostly down to looks, your budget and desired performance when finished.
 
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