Need stiffer rear springs for my MM700

[Oyvind Ryeng]

As some of you may know, I got myself a 2001 MM700 at the beginning of the previous season. Well enough maintained, 2-up, reverse, this guy here. After a full season of riding in 2008/2009 I now know what needs to be changed/modified as a first step:

-The steering bar height, it's about 2" too short for all of my 190 cm. or about 6' 3".
-The skis, which don't float worth a damn in the powder. They're awful, just awful.
-The swaybar needs to be removed and holes blocked off, it takes far too much effort to "throw it around" even when applying careful countersteering technique.
-Some kind of transfer enhancement kit for the rear suspension so I can lift the skis more than 0.01 mm., or less than four tenths of a thousand of an inch, which is highly useful for crossing small creeks and the like.

And the entire point of this post: stiffer rear springs. I'm pushing close to 100 kilograms, or 220#, the seat is a 2-up-type and the tunnel is fitted with both a hitch with reinforcement bars and a rack, all weighing it down. When I'm also carrying a passenger the stock springs will just simply collapse in anything more than the smallest bumps, and with a transfer enhancement kit fitted the suspension will be uncoupled and even more prone to bottoming out.

So I ask you guys, to "hook me up", as you say. Is there a simple solution like OEM Pro-Action Venture springs/dampers, or is aftermarket the way to go? From what I've gathered from viewing the parts catalogue over at Port Yamaha (thanks for the V-belts; you guys rock) an optional rear spring exists, but there's no data on the spring rates. If possible, a stronger center spring would also be of interest; the one on my sled now seem to be meager at best and I imagine the sled will be a little more fun to handle with a stiffer "balancing beam" at the tipping point in the middle of the sled. I realize a stiffer center spring might cause a little more trenching, but over here in Snoreway we don't get the insanely deep powder you have over there in the North American mountain ranges.

Let me hear your thoughts on this, guys.

 

[bluewho]

First thing i would do is pull the suspenshion out and look for play in the bushings.

The smallest play in them will cause the back end to sit lower leaveing a smaller gap in the top of the transfer rod.

This will cause it to bottom out and not give you any ski lift or transfer.

Play in the front bushings will keep the front end sitting lower and puts more weight on the skis.

I dont think the srings go weak they are just to massive in the rear of the sled.Shocks on the other hand do need rebuilding over the years.The centre one will go first.And you can tell when the skid is out by standing on the front w arm and trying to collapse it.

 

[Oyvind Ryeng]

OK, I'll try and inspect the suspension bushings and shock absorbers, but all things considered, it seems to me that I'm loading up the back of the sled with ~300# more than it was ever designed to carry, and therefore, the spring rates must be too low by definition. I'll be sure to check out the bushings, but I just don't see how the condition of the bushings is even measurable when compared to the strength of the springs which supports the entire weight of the rear of the sled directly... Help me understand, won't you?

The center and rear suspension springs are already at max. preload and the off-center bolt in the middle is also put to it's hardest settings. No dice, it still bottoms out without even trying when riding 2-up.

 

[norwegian]

The first thing you need is a shop manual for this sled:
I believe the stock rear shock spring is like 2,8-4,3 kg/mm? something like that.

The optional springs are 3,0-5,0 and 3,5-5,3. You will need other shocks.

Say an engans (gas) rear shock with the stiffest yamaha spring. Or you could get some viper shocks, they will bolt right on, I have this from a reliable source. You could probably get some cheap here. I bought this set up for a buddy of mine but we haven't tried it out yet.

Or, you could buy WP shocks from finland, these are expensive, but they are tough.

Hartman inc also makes shocks for this sled, I got that confirmed by Richierich here.

As for weight transfer, you could order one from MPI, or get a set of used srx rods (has to be 00-02 rods). I have maxx perf rods on mine. Dial them to 4 (out of 6) lines and you're good to go.

 

[gild]

Fra

The FRA is set to the stiffest setting?