I have just longtracked a 98 MXZ 670 and it seems way to stiff even at the lowest rear spring setting. The color of the springs is blue/blue/blue. If someone knows the specs on these springs I'd appreciate it.

I think that the diameter is 10.6mm (99% sure about that one). *As for the angle I am unsure but it may be 90 deg.

I'll get the racing manual when I get home. What is the long track suspension out of?

What I did was take summit 136" rails and layed the 121" over them and marked the holes. I drilled the 136s and transferred everything over. Now I can hardley push the rear of the sled down.
I took the rear springs loose and the suspension moves all the way to the bottom freely, so I dont have any binding problems. I'm kinda lost for what to do except find softer springs. Thats why I was looking for the specs on whats in it so I`ll know where I'm starting.
Thanks for any help, Don

According to the race manual the stock rear springs on the 670 are as follows:

LH 414 943 600 *RH 414 943 500

10.6 mm wire dia., 90* opening angle, WH colour code

The optional softer spring is:

LH 414 866 300 *RH 414 866 200

10.3 mm wire dia., 85* opening angle, YL colour code

The '98 Summit 670 came with these springs standard.

The blue springs are the stiffest you can put on an SC10. That is why they seem stiff.

actually the springs from the 99 MX6 are stiffer yet (11.1 mm in diameter). *I know as I went to the softer (* MXZ 670 springs on my sled after fitting a coupler kit. *don't mean to be a know-it-all but that is a fact. (not sure about the colour code of the opening angle, however)