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85 Formula Plus Track to 121" HELP!

596 Views 5 Replies 5 Participants Last post by  popcorn popper
Who can help on this I want to convert formula plus to vintage grass dragger for fun and want 121 track vs. 114 I think stock. Possibly big wheels also. I will need tunnel ext for sure and probably rail too...anybody make these parts or know who I could ask or how do I doo it!

Many thanks
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Who can help on this I want to convert formula plus to vintage grass dragger for fun and want 121 track vs. 114 I think stock. Possibly big wheels also. I will need tunnel ext for sure and probably rail too...anybody make these parts or know who I could ask or how do I doo it!

Many thanks
Hello Gade
I have a 85 plus and i did this mod about 10 years ago,its quite simple as i bought a new at the time 1 inch full block with the internal drive setup.The rails and everything fit perfect,After running the track for some time now I wish Iwould have went withextrovert sprockets as the internals like to ratchet under hard exceleration.I just grass dragged this sled last weekend in vintage and placed second in a 15 sled field.Ilost to a srx in the final as I had a bad bog on holeshot,this has been fixed and am looking forward to the snow drags.Also I did not need an extension for the tunnel.
Steve
I thought that the 85 Plus has a 121 originally.
the 85 has a 114" track you would have to relocate the rear suspension or find a 90 rear. they went to 121" in 90
I put a 121" track on a '86 MX years ago. I used the rails from an '89 Mach and welded tabs on the rails to mount the rear scissors to. Also had to make a new snow flap bracket to stop the track from hitting the snow flap.
I put a 121" track on a '86 MX years ago. I used the rails from an '89 Mach and welded tabs on the rails to mount the rear scissors to. Also had to make a new snow flap bracket to stop the track from hitting the snow flap.
Yes you guys are right,I also had to add to the back of the rail.At the time i just got an old wrecked rail and cut the back end off where the axle mounts,drilled some holes and bolted it to the back of the original at the length i needed.I just hooked a small chain on the flap to keep it from flipping in as it was fairly close.If you think of square inches of track your not gaining ,the only benifit at the time was lug height,15by 121 gives 1815 and 16.5by 114 gives 1881.I guess now you could go to the 16 wide tracks.
Steve
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