RXPro

Kachess1 · Jan 10, 2018

We've been throwing around lightened RX-1's (~530lbs) in the Cascades since 03. Still have 9 running strong. Well, I'm ready for a new sled. I love my motor: feels like high 140's hp with our mods, super reliable, still out runs new 800's on the road. I have no interest in going back to a 2-stroke or spending $13K on a new sled. I have yet to see a new naturally aspirated 4-stroke that can touch our sleds in the mountains. My opinion. the low hp nytro motor was a bad move for Yami. So I decided to mate my favorite motor with what looks to be the lightest, most similar handling chassis out there. Plus, with lots of blown pro motors there's lots of cheap Pro chassis's. Mine was $2.5k. (My son just picked up a 2014 Pro 155 chassis to mod for $1300). I yanked my ole trusty sled's engine this past summer (over 12k miles on it but still running strong), and stuffed it in a 2016 RMK 155. The install was amazingly simple, even for a low-tech guy like me. A little grinding, some simple engine mounts from 3/8 6061 plate, basic wire feed welding on the stock under-tunnel exhaust. Engine looks more at home in the Pro chassis than in the one ton. Lots of space for crap. I'm at 469lbs, no gas. The stock RMK was 461lbs w/oil, no gas. A true Pro chassis will be lighter. I have it on the snow. It's running strong. Had to tighten the track ridiculous tight to not ratchet. Very happy so far. Feels like a Pro with great motor. Just need some real snow in the Cascades!!

Kachess1 · Jan 10, 2018

Couple more pics.

BeartoothBaron · Jan 10, 2018

That's quite a combo! I'm surprised it fit without too much trouble: I'd have thought the RX motor would be quite a bit wider (never seen one in person though), and every new sled I peek under the hood of looks super cramped. You could swap about anything under the hood of my EDGE RMK – and I love the fact that they're generally indestructible – but the weight and dynamics of a Pro coupled with the number of low-mile examples just needing an engine makes them a great frankensled candidate. I've seen a couple around here, but in the $4-5k range; if I found one for <$2k, I'd be very tempted to snap it up for a motor swap or rebuild.

XCaSSAULT · Jan 10, 2018

WOW!!! That’s sweet! Nice work! Any YouTube vids yet?

pus1100 · Jan 11, 2018

Have you thought of fittings the Apex motor in there? Wonder if the throttle bodies will have room enough?

Kachess1 · Jan 11, 2018

One of our group's riders on a lightened Apex just picked up a 2012 Assault with a blown motor last week for around $2.5k. We'll see how she fits. One SW member put a Nytro motor in a pro in 03 and turned the throttle bodies down using boots. Nytro motor's taller than one ton/Apex motor.

Dumping in the Mountains today so may have some decent riding this weekend!

Kachess1 · Jan 15, 2018

In typical Cascade fashion we received 3 feet of snow followed by 3 inches of rain. Finally poked up the hill behind our place today and my 115lb son messed around on the sled for about 20 minutes on a very crappy hill. Ran strong. Way more nimble than our one tons. Going to take some getting used to. Track still ratcheting. Cant believe how tight we'll have to run this thing. Looking forward to some better snow.

https://youtu.be/Ssk50cAhgVk

https://youtu.be/kubrayev9MI

Kachess1 · Feb 20, 2018

Wasn't getting full power for a few rides. Even fouled plugs which is something our fourstrokes never do. After trying everything finally messed with the inlet of the airbox and she started to run normal. I had had to cut the normal air box down to fit in the chassis and it seem to affect air flow. I ended up having to restrict the intake to get the CV slides to retract fully. Handles like a dream. Seems to be producing full power now. Now we think it needs little more track for the deep stuff. Thinking a 159 might be a happy medium.

Watch "Sidehilling the RXPro" on YouTube
https://youtu.be/o8pyUberePo

XCaSSAULT · Feb 20, 2018

Love the vid! The thought of running my poo 800 like that (to the boards for that long) gives me a pain in my wallet! Lol

Octanee · Feb 20, 2018

This is a cool project! I loved my yamaha apex, mind you it was on boost! But they are a boat, that thing on 19# (with the head shim) went like no other and the sound of the in line 4 on boost is just an ear gasm haha, but alas she was still a tank and I eventually had enough.

I do miss the sled. I bought a turbo pro to replace it, the power sure lacks in comparison, but it does get up and go good still. but I sure do appreciate the light weight though, I feel like I can enjoy riding more with out the worry of getting the anchor stuck.

One thing to keep an eye on since you mentioned the ratcheting g issues.. is your jack shaft and drive shaft! I've snapped both! They are weak in the pro's, a hollowed out shaft with solid end shaft pieces put together with a poor welding job where it'll fracture. The drive shaft is made super light as well, the weld is a joke, I sheared mine off, I got a replacement and welded it up to reinforce it. If your having issues ratcheting and the track is tight, I'd bet you will also come to have a broken drive shaft soon. And that really sucks! A jack shaft is tow home, a drive shaft and your tracks locked up.

Get some avid drivers for the sled, that should fix the ratcheting and you can run the track loose again. Beef up the drive shaft as well.

Kachess1 · Feb 21, 2018

I found this company that manufactures hex shafts with Wahl drivers pressed on. Are there any other sources for an aftermarket drive shaft with drivers that won't ratchet and I don't have to worry about breaking?

Octanee · Feb 21, 2018

Kachess1 said:
I found this company that manufactures hex shafts with Wahl drivers pressed on. Are there any other sources for an aftermarket drive shaft with drivers that won't ratchet and I don't have to worry about breaking?

I don't know of any, if there was I'm sure my sled would of had it in it already. If you get the avid, or Wahl drivers, you shouldn't have any issues with it ratcheting anymore. And a looser run track is not going to stress that driver as much and bearings. I'm sure after welding up the stock driveshaft, one shouldn't have any more issues.

Kachess1 · Feb 21, 2018

Forgot to post the link:

http://ftxmotorsports.com/parts.html

Anyone have experience with these Pro shafts?

Octanee · Feb 22, 2018

Kachess1 said:
Forgot to post the link:

http://ftxmotorsports.com/parts.html

Anyone have experience with these Pro shafts?

I should of better read your first post, you said a 2016 chassis. I had looked at the photo and assumed it was the older model of pro, so what I had said is irrelevant lol! :yuck:

They list that shaft for a 2013-2015? Not sure if it'll fit, maybe the 2016 pro they fixed their driveshaft issue, 2013 had a horrible design of one, worse than the 11-12's.

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