FCX Fan Cooled Xtreem CMX

Starting on a sled for my kids to ride because Polaris wont make a light weight mid size sled that goes thru powder. This wont be mid size but I hope to get it down bellow 400 Lbs. My daughter will be 10 this year and the 120 is just to small wont work in powder and she is getting to big to put in front of me when we go in the back country.
Starting with a 2006 CMX that I bought as a roller. The 151 track and M10 is out and will be replaced with a 2013 Polaris skid that will be shortened to 141 with a 141 X 1.6 Cobra track. Have a 440 Polaris fan engine from a donor sled. The Coolers are out and I have some Burant boards that I am trying to make work. Here are some picks of the mods needed to make some NOS 141 rails work.

Working on the rear skid today. The 155 skid weighs 40 Lbs without scratchers and 43 Lbs with. I am hoping that it won't gain any weight with the splice plates, and less cut outs than the 155 rails. I might have to go with the cable style as there is no place to drill the second mount hole. Does any one know how much the cable style weigh? Made a new rivet back up buck tool and finished riveting the new front arm mounts in place. Riviting process is working better now. (Hope the front arm mount is strong enough) Transferred punched the arm mount holes to a template, drilled the template, and then transferred to the new rails. Drilled them out and used my new counter bore tools to make room for the lower mount point bolts and shafts. The new placement of the bottom out snubber for the front arm was going to hit the nut for the hyfax thru bolt, so I had to shorten the bolt, and drill a hole in the rail, so the nut is in the middle of the rail instead of on top of the rail. Still need to square out the rear axle holes so I can get full track adjustment out of the newer style axle mounts. For now I will be using the smaller rear wheels that fit these rails. There is not much extra room for the rear arm to clear the larger wheels. Will have to see how much there is when it goes together.

- What can you tell us about the 440 fan motor? Is it a reed valve motor? Why did you elect that size versus going with a 550 which would have 25% more cubes?

The 440 was chosen for cost. I picked up a complete sled for $200. There are no reeds on the carbs but it may have the reed petal boost port in the case. I think the bolt up and alignment are the same as the 550 so that could be an upgrade later.

-What steered you to the 141" track?

I was thinking about a 136 but the 141 cobra weighs 41 lbs which is lighter than most 136 tracks out there. The pro skid would not be able to be shortened to 136 as the rear arm would hit on the rear wheels. The 141 also could be upgraded to a Attak or power claw and only add around 5 Lbs. The 151 I pulled out was around 56 Lbs

- Do you anticipate any issues using the "Pro" rear suspension in a shortened version? I thought Polaris opted not to use that set up in the 144" platform since it would not work as planned (as it has in the 155/163)?

I chose the Pro skid for the weight. It is 40 lbs without scratchers and 43 with. This is lighter than the 151 M10 and a 155 Holz I had available. Polaris has offered a 144 in their 550 for 2014 that looks very similar. I think the previous 144 skid offerings were coupled skids that were better suited to trail use. They may have some new calibrations to make it work in this shorter version.

- How much weight do you think you can lose by reducing the over-engineering required for the weight and power of a factory 800 versus the 440 fanner?

The 800 power and weight items that will remain will just be added durability. As far as weight loss the cooling system was around 15 Lbs, the lighter track will net around 15 and the skid will get me 1 or 2 Lbs. I might lose 1 when I shorten the tunnel. I would think I could lose a few on the engine and another 8 without any coolant. I am also working on some different options to use some pro parts on the belt drive to shave a little more weight and to get closer to a 2.8 ratio.
- What width ski center do you plan to run given a smaller/lighter rider?

I have not thought about the ski centers and will probably just try it as is for now.

Here are a few more pictures of progress. Hyfax attachment nut relocation, Rear axle slots squared out now, the assembled 141 next to a 155,and the donor sled engine.
The larger stock wheels will clear the rear arm return stop but will require an axle relocation. 8" wheels installed in the current shaft centerline will hit if the arm goes down all the way but when they get moved up may miss depending on where the radius of wheel ends up. If the return stop gets relocated inboard 8" wheels will work. I weighed the finished skid and it weighs 39.8 lbs on the bathroom scale, the stock 155 weighed in the same so I am happy it did not gain with the splice plates and less cut outs in the rails. The front and rear arms are a little narrow for the wider tunnel that it is going into so I am thinking I will have to make some wider shafts and make up some spacers to keep it centered in the tunnel. The bottom out snubbers for the rear arm ended up a little short on height as the new rails are not raised up there. I will order up some like the ones for the front arm to get the needed installed height. After all this I think a call to Ice Age for some custom built rails would have been worth it.

*I did consider ordering a set of rails but was unsure of what size rear wheels to order for. This was cheaper if you don't count the time spent.

*I am looking at the material needed to make some longer cross shafts. Does anyone know what material they are made out of ? McMaster Carr has many options available.

*I have some 2011 but think I should be using something stronger like 7075, or the more expensive 7068. Any experts on aluminum out there?

The front and rear skid arm shafts that connect the skid to the tunnel.

joshkoltes said:

I used the original cross shafts last time I just built some nylon wear block spacers to take up the difference with longer bolts

Click to expand...

I was thinking about doing that with aluminum but thought it would be better to have the shaft make direct contact with the tunnel to be sure everything stays tight. I would hate to see it loosen up and start slotting out the mount holes. Is the nylon holding up and staying tight? What was your conversion on the skid swap, (skid donor sled and sled installed into).

Here are a few pictures of recent progress. The holidays and a trip to the snowy range has slowed progress. No electric start on this one. Got the engine out and stripped other needed parts from the donor sled. Got some aluminum bar stock from McMaster Carr, and finished a set of rear axle offset blocks to use some AC 8" wheels. Had to shorten the shaft and make up some spacers. The shaft is pocketed into the blocks 1/2". I was able to notch the blocks so I did not have to relocate the adjuster bolt brackets. My concern that the bracket on the rear arm would hit the larger wheel has been put to rest as it has plenty of clearance. With the bigger wheels all the way forward the track will hit the rails so I will have to trim some off the rear of the rails to allow the track to clear. Should be able to just match the cut angle from the stock Pro rails. Weighed the skid and it is now up to 41.2 Lbs (on the bathroom scale) after the 8" wheel/rear axle upgrade. I hate to be adding more weight but the larger rear wheels should help improve efficiency.

I started install of the engine. I bought an engine plate from a gen two 550 and thought it would be a direct bolt in but found that the 440 and the 550 do not share the same bolt pattern so new holes will have to be located. I am thinking I will try to move the center to center to 11.5" so I can use the same belt as the Pro. I will also have to make some spacers to get the engine up a little for clearance of the oil pump. I will also have to swap out the steering bellcrank with the one from the engine donor sled and modify the steering post accordingly. Switched gears to the belt drive as I will need the jack shaft in place to locate the engine. The CMX drive will not allow me to get to the gear ratio that I would like so I started on the new back plate for the belt drive that will allow me to repurpose a pro jackshaft, brake, and rotor. I had some bearing holders made at a local machine shop that will allow me to use a .250" thick back plate for the belt drive. There is also a Wahl Brothers one in the picture that I was considering using but decided to have some made that would allow me to install a grease seal and zirk to the keep the bearing in fresh grease. The pro tunnel is a not as wide as the gen two so the bearings needs to be mounted inboard as far as possible to use a Pro jackshaft. I sourced a set screw type long collar bearing to provide better support on the clutch side of the jackshaft as the normal press on bearing will now have a new location due to the tunnel width difference. I think I will be able to use the 2013 pro jack shaft but have one from a 2012 if needed. I purchased the belt drive parts from TKI. Tom was very helpful and sold me the parts I needed from his inventory of available parts. I will have to make some mods to the smaller tooth count sprocket as it is made for the chain case conversion, but the other two will work as is. We are talking about some smaller tooth count top sprockets that will get me down to 2.74 or 2.86 if needed. I will need to make a spacer to attach the belt tension arm for proper positioning also. I am drawing out the plate on cardboard to be sure it will work before it goes to metal. The other drawing is an offset mount bracket to attach the brake caliper to.

I am not sure if I will port the track. Ski doo quit porting their tracks and said their research indicated the floatation was better without porting. I think I will wait and see what the finished sled weighs when it is done.

I made some progress on the belt drive parts. The jackshaft will be moving up from its present location to use the narrower Pro jackshaft. The bearing needs to be placed inboard as far as possible, I considered notching the tunnel but chose to move it up instead. This created an issue with the shaft centerlines and the available belt lengths. The track shaft position will also move forward a little to keep an 8.5" center to center on the shafts. I will still have the same clearance to the front of the tunnel / bulk head as there is no longer a front heat exchanger in the sled. There are not a lot of options on belt lengths unless you are moving your center to centers an inch or more. Had to build a bracket to hold the Pro brake caliper to the back plate before I can finalize the size of the back plate. The design has changed from the one laid out on the card board to allow the brake to roll forward a little more and to have the brake bleeder above the brake line. If I roll it forward like the 13/14 Pro I will need to put a pull start rope diverter on to keep it away from the brake. I may be able to roll it back if it will clear the stuff back there but I would need to source a caliper from a 2012 Pro or assault that are rolled back. Does anyone know if the ones from the 12 pro with a chain case are the same with the exception of the location of the bleeder?

Here is some progress.
1 Made a template that has common locating holes in it from both the right and the left side of the chassis. This allowed me to lay out the shaft placement for both sides on one plate. Transfer punched the holes to the pto side, the belt drive side, and the shaft bearing holder plates that will attach to the sled.
2 Cut out new hole for drive shaft to slide thru when installing track.
3 Drive shaft installed. I could not believe the fixed bearing placement was only .055" from being in the right place. I found some Polaris bottom sprocket chain case shim washers that were the right thickness and shimmed the bearing to prevent side loading it. The drive shaft is from a fusion trail sled but I believe it is also the same as a 08-10 RMK. I was going to use a hex shaft and shorten it but this one is lighter and the only mod will be the shim to move bearing placement. I also have a 13 PRO shaft that I am thinking about using because it is even lighter than the hydro formed one but it will require a custom spacer be made, as it is not as wide.
4 Driven side bearing plate installed. I am also working on some ideas to get grease into this bearing, and make a new pick up for the drive shaft to send a spedo signal to the gage that came with the sled. I think it just needs a single magnet on the shaft and a pick up mounted to count the shaft revolutions.
5 Belt drive side with brake caliper in place. Still have more to do on the belt drive plate. Some of the bolt holes will need to get counter sunk for rotor clearance.
6 Still working on the new plate for the driven clutch side jack shaft bearing.