Jump to content

50mm KYB shock revalve recommendation

Recommended Posts

Need shock shim stack recommendations for 16 YZ450F. Went from stock 5.6 rear spring to a 6.6 kg/mm to achieve correct sag numbers. Thinking about adding 2 more face shims to both sides of the valve, 44mm x .20 and 40mm x .20. Not sure if that will stiffen up the valving enough for the spring rate change.  225 lb Vet Amater b/c motocross. Thanks for the assistance!

Share this post


Link to post
Share on other sites

Spring sounds too stiff.  6.3-6.4kg ought to do.

I would add 3-4 face shims on rebound and leave the comp alone until you get to ride it with the corrected rebound.

Share this post


Link to post
Share on other sites

Thanks GHILL28 for the advice. I have 4) 40mm x .20 shims I can put on the rebound base stack. Come to think of it I rode on Saturday with the rebound adjuster all the way in and noticed the rear felt like it was deflecting off a lot bumps and jump faces. Was reading up on how the rebound clicker affects the compression free bleed and stiffens up compression as well. Now I see it makes sense not to stiffen up the compression side of the valve. I tried a 6.3 rear spring first and was only able to get 95mm RS and about 30mm FS with that spring. I went to the 6.6 and was able to get 102mm RS and 35mm FS, the numbers I was shooting for.

Share this post


Link to post
Share on other sites

Those numbers don't add up , 95mm race sag if increased to 103 woukd give you perfect free sag

Share this post


Link to post
Share on other sites

Mog a friend of mine with the same bike recommended to set the sag at 95mm to get more weight on the front end to help it corner better. When I had the 6.3 spring on it, my spring preload was about 15mm,  95mm RS and about 30mm FS. I know I wanted to my FS to be 35mm - 45mm. Because of the 15mm preload on the spring and not enough FS  I went up to the 6.6. Instead of  setting the 6.6 at 95mm I went with MXA's setting of 102mm. With the 6.6 I have less than 10mm of spring preload and about 35mm FS. I might not have the exact numbers for my sag settings but based on the excessive preload on the 6.3 spring that why I went with with heavier spring. I think the 6.6 was the only next size stiffer I found.

 

Share this post


Link to post
Share on other sites

At 30/95, you'd be at 37/102 if you set the rider sag to the same point with the same 6.3 spring, which is why something isn't adding up.  Are the springs from the same manufacturer?  They do vary a bit.

This chassis like a bit of preload to the rear spring to help it unload into the front under braking.  I've been back and forth with this a lot.  32/105 I found to be a pretty nice spot for the 14/15 chassis.  The 16 has different triples so that may not apply.

  • Like 2

Share this post


Link to post
Share on other sites

My springs are from different manufacturers. I need to stiffen up the rebound valving some with either spring. I'll try the 6.3 again and see where I am at on the free sag after I set the race sag  at 102 to 105. You guys are probably correct about being able to use the lighter spring and getting in the free sag window of 35-45mm. Thanks for the assistance.

Share this post


Link to post
Share on other sites

Update
I ended going two steps stiffer on both the low and high speed rebound stacks. Came out 2 more from stock on the low speed comp. (12 out) and another 1/4 out on the high speed comp. from stock (1 1/2 out). Left the rebound on the stock setting (14 out). Set the sag at 95mm, got 25mm free sag with the 6.6 spring. Haven't ridden it yet, but hoping for an improvement with handling. I also found out upon disassembly I notice the last 1/4 to 1/2 inch of shaft extension it felt like it either had air in it or it was a little low on oil. 48 hours on it, never been apart. That could have been creating some problems with it as well?

Edited by Hutch215

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×