KDXRIDER.NET

trying to soften up the rear suspension on my kdx220 1998 model for my puny 60kg frame. got myself a spring from a yz125 which i believe to be 4.6kg,
this might still be too firm for the technical single track i ride, was thinking to lower it slightly with the klx250 dog bones,i had heard this would also make the suspension softer by changing the linkage ratio but i can't see how this would be so. wouldn't you have to change the linkage itself rather than just longer dog bones. what are your thoughts?

The most common reason to change the linkage dog bones is to lower the rear end. Longer dog bones will give a lower rear end.

The center distance for the stock dog bones is 112.5 mm. This is the number stamped on the parts. When substituting dog bones, weather from another bike, or making your own, the center distance is what matters.

Keep in mind that lowering the rear will affect the steering geometry; fork rake. Lower rear gives more fork rake.

Sorry, I can't comment on how different length dog bones affect suspension movement.

Hope this is helpful.

I run a 4.8kg spring and at 140lbs (63.5kg) and it works well for gnarly technical terrain. I think a 4.6kg spring should be spot on for your weight.

Still wondering about the change in ratio, I understand what dog bones do. Cheers

The change in ratio on the dog bone length just affects the amount of stroke you get in the suspension, in other words changing the length of the dog bones changes the amount of travel of the swingarm in relation to the amount of travel in the shock body. To soften the rear you have to change your spring weight and the associated settings (preload, PSI in the bladder). Lengthening the dog bones will lower the rear end, reduce the available amount of travel, but not affect the spring weight. If you don't need a lower seat height, leave the stock bones on there and spring it correctly for your riding weight. Do both ends as they affect the overall handling of the bike. As mentioned, if you lower the rear, you need to lower the front to keep your steering geometry balanced. Best to leave all the travel and get the right springs for your weight/ability level. Best money you can spend on your bike for performance on the trail IMO.

Thankyou that confirms what I thought. I know the linkage itself changes the ratio but not the dog bones. I already have the front set up perfectly for my weight with 0.32kg springs but I couldn't source a rear spring here in Thailand so had to wait until I went back to Australia. What Psi in the bladder should I run. When I rebuild the rear shock I will use 2.5 weight as apposed to 5 weight, most trials bikes run 2.5

Different length dog bones DO change the ratio, as it puts it earlier or later into the curve.

150 psi

2.5 or 3 weight is great.