Just installed sway-bar - now weird "tank-slapper" thing in powder

[Surestick]

I'm on a 2007 Phazer Mountain Lite that I just got this winter, it's my first sled. I'm in Eastern Alberta so no mountains and a mix of trail riding, and powder in fields and on lakes. Stock suspension on the sled that seems to be in okay shape (none of the dampers feels blown or is leaking oil).

It came without a sway-bar so I installed one as I really didn't like the unpredictable handling on off-camber trails and in turns. It made a very noticeable difference on trails and in turns but I ran into a weird problem a few times cutting across fields in ~1 foot deep powder. It would starts bouncing from one ski to the other in a way I can only describe as being like a slowed down motorcycle tank-slapper. It never did this before and was really well behaved in a straight line in powder. Letting off the throttle and hanging on would settle it down but it was disconcerting to say the least. This seemed to happen at around 40-70 km/h (25-40 mph) but might happen at higher speeds, I just didn't want to push it.

I couldn't say what the current suspension settings are but I could check. Nothing feels terribly off but it does bottom out in the back when hitting the bottom of steep hills. I'm still getting used to how it feels and reading up on how to set up snowmobile suspension before I start playing around trying to change things.

Any ideas on how to tame this bouncing ski-to-ski thing?

 

[kallholmen]

You probably got your skis set with toe-in instead of toe-out. The Phazer need pretty much toe-out.

 

[maxdlx]

Do the phaser mtx and flat land phasers have the same length a arms.

 

[Surestick]

You probably got your skis set with toe-in instead of toe-out. The Phazer need pretty much toe-out.

Skis are toed out. I think that's what keeps it from flipping when this happens. One ski hits the ground toed-out, pulls the sled to that side which brings the other ski down but then it bounces back onto the first ski and the cycle repeats.

I believe the mtx A arms are shorter.

 

[maxdlx]

Did you use a flatland sway bar on a man sled?

 

[Grimm]

You may want to soften the front ski shocks. My understanding is that when someone removes their swaybar, they crank up the stiffness on the ski shocks to compensate.

 

[Surestick]

Did you use a flatland sway bar on a man sled?

Possibly. I don't see why it would do this, the non-mountain one is a bit stiffer iirc. I was actually debating getting the Schmidt Bros. one but found a used Yamaha one on ebay.

You may want to soften the front ski shocks. My understanding is that when someone removes their swaybar, they crank up the stiffness on the ski shocks to compensate.

True... I'll try backing off on the preload.
Of course all the snow is melting here right now. +10C for the past few days.

 

[maxdlx]

Is the mtn sway bar shorter than a flatland.

 

[Surestick]

Is the mtn sway bar shorter than a flatland.

I don't believe so. Everything lines up properly with it installed. The links are in the same position and angle as they are in photos of others and there's nothing loose.

 

[blueironranger]

For some odd reason the MTN bar is the stiffest factory bar. I'm a 50/50 rider and swapped in GT arms (2" longer) and GT adjustable sway bar onto mine for better trail manners. I run the GT bar in the softest setting. I also agree that you may have a toe-in issue that's causing the side to side in the powder, I like running 1/2-3/4" tow out on mine. Also the ski mount bushings in the spindles get loose which makes for a lot of freeplay.

 

[Surestick]

I checked the skis. They are toed out as they should be.

I did notice the carbides were almost completely gone, about an inch of carbide left on one and less than half an inch on the other. They've been replaced but unless it snows I won't be able to test until next winter.