141 Pro RMK

Bushwacker1

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Nov 27, 2008
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Crazy cool build please post some video. I am so impressed. Makes me wish I weren't taking the chickens way out starting with a 550 polaris lxt 144". Super inspiring for sure!
I am glad to provide inspiration to others for their projects as well as sharing my own projects. Starting with the LTX is a great plan. You wont be bogged down designing and making parts like I have which just seems to take forever. There are lots of Pro RMK parts available that will let you build a much lighter sled than what you are starting out with, and you can also do it in stages if you want to spread out the costs over time. You will be able to upgrade that rear skid to the better Walker Evans shocks also. Other things keep pushing my project back so it will be a while before this thing gets done, tuned, and validated. I still need to get back to finishing my new motor mounts (about 75% done now) and a revised air box and the other revisions I had planned. My kids are already ready for more power than this one will provide but I still want to finish it. They rode their Indy Evo's when we went out west this year that I installed longer tracks to and they worked well. Both have the same 550 144 rails you will be using with Walker shocks. One has a 146 x 1.75" Hurricane track with an offset axle, and the other has a 141 cobra 1.6" with some minor rail mods and 7 tooth drivers so you have a lot of options on tracks for your project. The 144 with 2.52 pitch tracks work well but are heavier than the 2.86 or the 3" pitch tracks. I think the Power claw 141 x 2.25 would be the best powder track for a kids sled when you consider the weight of the track (around 46#) and their performance in the deep snow. I posted info on the 141 conversion a while back that may be of interest to you and the issues getting a 141 to work with those rails. I am already thinking about how to get an older Fuji 500 engine into one of these Pro RMK chassis to get the power up to the 80 Hp level and still be under the 400 lb mark. I am currently bogged down on some other projects but plan on posting updates when more progress is made.
 

TRS

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Dec 1, 2007
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What a great build thread.
Congrats to your perseverance. Many would have quit.
I’m planning one with a PSI 995 cut to one cylinder.
 
Feb 21, 2008
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Chanhassen MN
I was looking to make gears but as you did but realized I would come up short and bought a tki kit that had the same ratio as my stock chain case. I would like to pick your brain on how you did that still.
 

Bushwacker1

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I started with a TKI kit and Tom was able to supply a custom gear ratio as low as 2.75 : 1 from his off the shelf items for a quick drive back plate. He was very helpful to get me to a deeper ratio than the stock quick drive provided. I still wanted to get closer to 3.0: 1 but he did not have anything available on the shelf. For him to design and make only a few larger bottom sprockets was expensive. I also wanted to get to a smaller tooth count on the top sprocket than he had in stock. I then started searching and was able to find a shop that has the needed equipment to machine the sprocket teeth. I then designed my own hubs and sprockets and had the blanks machined, then had the teeth machined on. It was still more expensive than buying off the shelf but when there is nothing available you don't have many options. For your 550 engine I would think a 2.75 ratio would most likely be good for even a deeper lug 2.5 144/146 track, but if your kit is a chain case kit (opposed to a quick drive backplate) you will be limited on how big of a bottom sprocket will fit in the case. For my 250 cc engine I was concerned that 2.75: 1 would be over geared for my 141 1.6 and my clutches would never shift out. 7 tooth or even 6 tooth drivers are also an option to get lower gearing but increases rolling resistance and track attack angel will also increase. I now have options to test once I get the new sprockets mounted and determine that the take up idler will not need modifications. Just need to get back to this project before the snow flys again.
 
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