Secondary not backshifting

[NoSecondChances]

My secondary is not backshifting. As soon as the primary grabs the belt and moves the sled ahead about 2 feet, it pulls the secondary open and the belt slides down between the sheaves. I took it apart, pulled the spring, seems fine, not broken, replaced the nylon sliders just in case, cleaned all parts, re-assembled with about 15lbs preload and it still does it. Track is loose and nothing seems to be binding, I'm able to turn it by hand fairly easily. I changed the spring and the pins in the primary when it first began to do it, so I put the stock ones back in, and it still does it so I know its the secondary. Seems like it just wants to shift out as soon as it has any load on it. On the track stand, runs ok and seems to backshift OK, as soon as I stand on the running boards and get some weight, just pulls it down. Seems like it needs more preload but the spring scale says otherwise, but I am able to push the helix into the clutch sheave with my thumbs. Secondary has always been the part that I know least about, am going to pick up another one today hopefully, and try it out just to make sure that it is the 2ndary, but wanted to see if you guys had any opinions on what it could be. Maybe just worn out? Doesn't seem to have a lot of play in it (just by hand). I'm going to fully rebuild this one if I can get a working replacement so I will have a spare.

Thanks for any help.

 

[winter brew]

You have to preload the movable sheave 1/3 of a rotation before pushing the helix in.

 

[NoSecondChances]

You have to preload the movable sheave 1/3 of a rotation before pushing the helix in.

Thanks for the reply. Yep, I did preload the moveable sheave to where it was before I dissambled it (everything was marked before dissammbely just to be sure). Spring started on A4, is on B6 now, seems like it has more than enough preload and even the guys at Ghostrider in Fernie cranked the spring up from B2 to B6 when they were trying to help me out, still didn't help at all. I'm thinking the spring is shot?, seems like the only option left, just won't hold the sheaves apart. Thoughts? It has a 50 degree helix, one guy I talked to said that is way to steep, should be more like 44 or 47. Ski Doo recommends the 50 though in the High Alt settings manual. Ran great all last spring and all this year with the exact same setup, all of a sudden when unloading last weekend off the trailer, just started pulling the belt right in. has the beige spring too, 45lbs and 90lbs. Hopefully I can pick up a spare one and figure this one out in the meantime.

 

[winter brew]

I would be suspect of the spring slipping out of one of the holes, even with a super soft or sacked out spring it should work "OK" just not backshift too well. I would almost put $$ on the spring coming out or not enough twist at assembly. 50* is a bit steep for a mountain sled but nothing unusual.
With the clutch in your hands, can you rotate the sheaves and they spring back instantly and smoothly?? No binding like a spring hanging up?

 

[NoSecondChances]

With the clutch in your hands, can you rotate the sheaves and they spring back instantly and smoothly?? No binding like a spring hanging up?

No it seems OK, not binding, returns to position OK, maybe I'm overlooking something simple....

Thanks