Are XS650 / SR500 Forks Interchangeable?

[RonXS]

Bouncing this question off the forum...
The forks on my XS650 are a bit pitted in the upper range of travel. Due to the leaky fork seals, the lower half is in good shape.

I have an extra set of good forks from a SR500 in the attic. Both are off 1979 bikes. I believe the SR and XS are both 35mm. Is this a simple swap or are there other differences I'm not aware of?

 

[5twins]

Yes, they are virtually the same except for different springs. But it's a simple matter to swap your 650 springs and adjustable top caps into/onto the SR forks.

 

[RonXS]

Thank you 5twins

 

[5twins]

If you compare the parts diagrams of the SR500 and late model XS650 (35mm) forks, you will find all the major components are the same. This includes the lowers, tubes, and damper rods. The only real difference is in the springs, their associated preload spacers, and the top caps, but all that stuff is easily swapped.

 

[SparkyJ]

If you shorten the tubes 2 inches, or have a set made that are 21", do you only need to cut the top of the springs?

 

[arcticXS]

If you shorten the tubes 2 inches, or have a set made that are 21", do you only need to cut the top of the springs?

Cutting springs will always increase the spring rate, i.e make the springs "stiffer". It may also result in "coil bind" (spring windings bottoming out on each other) if fork travel stays the same. The best way would be to remove the two inches from the spring spacers. But make sure you still have clearance between front tyre/ fender and exhaust pipes/ cylinder head, when fork is fully compressed, and also at fully compressed and at full steering lock. Otherwise you may have built a death trap....
If I wanted to lower XS forks, I would just add spacers to the damping rods, one, max two inches....And cut the spring spacers to achieve a suitable "laden sag"

 

[5twins]

Also, be aware that adding internal spacers on the damper rods reduces the fork travel by however long the spacers are. That means adding 2" spacers will reduce the travel by 2".

 

[gggGary]

If you shorten the tubes 2 inches, or have a set made that are 21", do you only need to cut the top of the springs?

You don't go around corners?

 

[SparkyJ]

Cutting springs will always increase the spring rate, i.e make the springs "stiffer". It may also result in "coil bind" (spring windings bottoming out on each other) if fork travel stays the same. The best way would be to remove the two inches from the spring spacers. But make sure you still have clearance between front tyre/ fender and exhaust pipes/ cylinder head, when fork is fully compressed, and also at fully compressed and at full steering lock. Otherwise you may have built a death trap....
If I wanted to lower XS forks, I would just add spacers to the damping rods, one, max two inches....And cut the spring spacers to achieve a suitable "laden sag"

Thanks for this. I have not had the forks apart yet so I will need to lay this all out and visually figure this out. I do have the forks raised in the tree 1 inch now, without issues. And I do appreciate the death trap comment. Certainly don't want any interference or geometry issues. Looking at this drawing, where would I add spacers to the "dampening rods"? https://www.cmsnl.com/yamaha-sr500-1980-oceania_model8748/partslist/D-09.html

 

[Raymond]

I'm interested in this. A few years back, I invested in a s/h SR500 top yoke. The SR500 top yoke is flat, but the XS650 one has the fork pinch bolts lower than the steering head pinch bolt. I've read that fitting the SR500 one will lower the front of the bike, giving the bike a better posture and weight distribution. Been trying to work out how that will affect the geometry of the XS650 but the thing that has given me pause, okay, my excuse for not having done anything with the SR500 yoke, is worry that the bottom yoke might be too close to the mudguard. A solution might be reducing the fork travel. Watching.

 

[arcticXS]

I'm interested in this. A few years back, I invested in a s/h SR500 top yoke. The SR500 top yoke is flat, but the XS650 one has the fork pinch bolts lower than the steering head pinch bolt. I've read that fitting the SR500 one will lower the front of the bike, giving the bike a better posture and weight distribution. Been trying to work out how that will affect the geometry of the XS650 but the thing that has given me pause, okay, my excuse for not having done anything with the SR500 yoke, is worry that the bottom yoke might be too close to the mudguard. A solution might be reducing the fork travel. Watching.

As the stock "Special" headpipes are different from the "Standard" pipes, I wonder if they are more likely to interfere with the tyre/ fender when lowering the front

 

[SparkyJ]

Wow, look-y here!

How-To: Rebuild XS650 Forks / Install Lowering Kit​