Has anyone converted a Polaris Trail Boss back to a Scrambler 250 R/ES?

[Nick_R_23]

Now that it’s spring time, all the cheap projects are showing up on Marketplace and I currently have a dangerous lack of self control on buying things. :D I ran across an older 4x2 Polaris Trail Boss 250 R/ES. My understanding was these were originally Scrambler 250 R/ES frames with an extension welded to them, similar to the old Astro 4 wheeler conversion kits, and utilized a complete Yamaha 225DX front end. If I’m remembering this correctly, I should be able to purchase the Trail Boss, cut off the frame extension, source a 225DX front end, and essentially have a “factory” Scrambler? Has anyone attempted this before?

[ATC King]

That's great idea.

You could look and compare parts diagrams to get a better idea. I did quickly look for bare frame images but didn't find any old enough.

If your were to go through all that trouble, why settle on a DX fork? It's not going to be original, or factory anyway. Something better and with a disk brake would be more worth the effort. I think those come with a rear disc, may as well have some symmetry by adding one to the front.

[dirtwheels]

It's a cool idea, but looking at an image I found of a trail boss frame and the parts diagrams, it appears the head tube is different on the quad version of the frame. Looks like it could be a smaller diameter and also has a different rake, almost vertical for the steering tube. So you would need to cut off the head tube and weld on a Yamaha head tube at the correct angle to make it work. The rest of the frame, like you mentioned, it looks like you can cut off what you don't need. you may be able to run the tank from the quad (if the forks don't hit it) until you can find a scrambler tank. I believe the seat is the same.

271727

[dirtwheels]

271728271730

[Nick_R_23]

I was under the impression that the same “base” frame was used for both, and that Polaris used the steering stem tube as the handlebar post guide. This picture here looks like it’s a full size head tube. https://www.3wheelerworld.com/album.php?albumid=2717&attachmentid=245084

[dirtwheels]

It's possible that is true and that would surely be ideal for a conversion, but it's difficult to confirm without better images of the 85-87 trail boss frame. They used a steering column post in place of the steering stem and it slides into a plastic bushing where the top bearing race would normally sit, but the bushing looks a little taller than a bearing and race would be and you would think they would have bushing on the bottom side to capture it, so it's hard to confirm what is going on without seeing it in person.

[Nick_R_23]

I found a local one to potentially try to look at. It looks like the 85-87 and some 88 frames (with the “Trail Boss 2x4” designation) were based off the 3 wheeler frame. New steering bearing kits with races are available for the DX, and AllBalls makes a tapered bearing kit, so that potentially solves the problem of bearing races likely missing on the Trail Boss frame. Does anyone have a Scrambler frame they could measure the overall frame steering tube height from?