82 trailfire 340 121" Rubber track swap

[mnjd4life]

Hello Deere Masters,
I am finally starting a project I said I was going to do years ago. I have studied what wycrumb did in his "121" Track on a Sportfire" thread and want to attempt it on mine. So far I got the skid out (snapped both back mounting bolts), and got the drive shaft out (what a joy). I have a local snowmobile guy in Erskine, MN that should have everything I need. I will be looking for a mid 90's Polaris skid and track and then find correct drive sprockets (1.105-1.125", 7" diameter). My main question is what gears should I go with. Since I believe wycrumbs was a 440 and mine is only a 340. Also I have a stock Chain case in there so no tensioner. I am not sure what the stock ones in there were but I might go check at lunch. Another question was did he take apart the new skid and reassemble using the stock 3/4" shafts from the deere, or did I read that wrong. My skid is almost total junk, but I can see if I can salvage those shafts.
That thread was pretty old so I also wanted to post this to see if anyone found anything else that worked such as the right length shaft or other drivers. Any input is appreciated!

-Casey

[mnjd4life]

Update:

My driveshaft actually measured to be 1.150 inches, but it is really rusted. Hopefully I can still squeeze drivers on there. Bottom sprocket is 35T, Top is 17T, and a 31 link chain along with 6" drivers. So I am already siting at a 35t:17t = 2.05:1 gear ratio. Now if I put 7" drivers on top of that should I be worried. Again any insight is appreciated, this is my first time doing anything like this.

[markzrt1]

Did the same swap to my 1982 trailfire 340 last winter. I used a early to mid 90's Polaris suspension and drivers from a 98 or 99 ski doo. I bought a 12 ton press from harbor freight to press the old JD drivers off and press the new ski doo drivers on.

As far as the shaft. I used the JD shaft, Had to order new from New breed parts. The JD shaft is wider than the Polaris. Slide the Polaris shaft out and put in JD shaft. I never did change the gearing and it does ok.

[markzrt1]

[mnjd4life]

Thanks Mark! I really appreciate the reply, just another confidence boost. Were you able to mount it in your original rear mount? And is that the location of the shaft we keep talking about that we keep from the original, the shaft of mine that has two broken bolts in it lol.

[markzrt1]

I believe I did use the original mount for the rear. I think it's the front shaft but maybe it was both. I don't remember. The bolt broke on mine too so that's why I ordered new ones.

[markzrt1]

You should sand the rust off the drive shaft before putting the drivers on. They go on hard but do-able.

[AirborneX4Special]

How does the 340 perform turning the thicker and heavier track?

[markzrt1]

It actually perform pretty good. I used a track from a 2002 MXZ with a .88 lug.

[AirborneX4Special]

Power was one of the supposed criterion as to why the Yokohama track was never deployed on a Trailfire. Knowing the way things operate at the corporate level, cost per unit would undoubtedly play heavily in any decision of this magnitude.

[mnjd4life]

Thanks for the help so far. I ordered a new shaft and clutch puller from new breed. I also went to the local doo dealer and we looked up some drivers and ordered a pair. They might be backordered but if they work I'll have to let you know. $25 a piece new.

[markzrt1]

I got my drivers used off ebay.

[sledhead16]

I'll look at this 84 Trailfire 440 I have, it's got a polaris skid and track in it, I can tell you new tunnel holes were drilled for all four holes. You will wanna keep the torquey 2.05 gearing because that motor will have to work harder to spin that track.