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So I picked up yet another project, this time a 2012 Switchback Assault 800. The engine is blown, one piston dropped a skirt and broke off the cylinder skirt, which the crankshaft used to punch a very large hole in the crankcases. Usually I’ll have these welded up, but this one suffered some pretty severe damage and I want to upgrade anyway.

I’ve had many different Pro Ride sleds, but I’ve always wanted to build a special Switchback Assault with a few custom touches, basically the machine I thought Polaris should’ve built. This machine is pretty much stock with the exception of Ice Age tails and a 146” Series 5.1 2.4” track. It also came with Sly Dog skis, which promptly got thrown in the trash and a set of new take off Gripper skis mounted up.

Since the original engine is not worth saving, I’m starting off fresh with a better setup - 2013 crankcases and cylinder, for better strength in the skirt area. The heart of this build will also be an Axys 800 porkchop crankshaft to give it more punch and quicker revs. SPI pistons with the oil grooves for better lubrication. I’ll be replacing the injectors and everything else will remain stock.

The chassis is in pretty good shape and the track setup is perfect for the type of riding I do and the wide range of conditions in my area, and was one of the big attractions for me purchasing this particular sled, as I wanted a little more than a 2” paddle. I have a wrecked 2015 Terrain Dominator chassis I have been saving, which has a good Quickdrive backing plate that will be transferred over to this sled, as well as all the necessary parts to complete the Quickdrive conversion, some of which actually showed up today. Conversion parts include Pro RMK aluminum driveshaft (machine already has standard RMK driveshaft due to the 2.86 pitch on the 146” track), Quickdrive specific jackshaft, upper and lower sprockets, new Quickdrive belt, all new hardware for sprockets, and the correct brake caliper and brake line.

This will be somewhat of a slow process since the person I have weld my crankcases is out of state until the end of the month, but I’ll be hopefully working on the chassis in the meantime. I may just strip it down and pressure wash it because it was sitting outside for a few years and is pretty dirty.

Also, the stock side panels and hood are beat up badly. Long cracks and large chunks of plastic missing, so I’m experimenting with the leftover Terrain Dominator side panels and hood on here as a replacement set. So far reception has been good, the colors match very well and are less headache inducing than the stock 2012 graphics. I think the red and white on the seat, ski hoops, springs, and A-arms really work well to bring the package together. I think I’ll stick with these panels and hood even though I know I’ll get a ton of grief because it still says PRO RMK on the side. Oh well, at least the price is right! I’ve also changed out the rear bumper to an all black unit to match the SBA style front bumper.



 

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Finally making some progress on this project. Traded out the 2012 crankcases and cylinder for a nicer 2013 pair I had stashed away with less damage down below. Got the 2013 cases back from having the cracks and hole welded up.



Also installed a new oil pop off valve





Upgraded to the porkchop Axys 800 crankshaft



Polished the center drive gear to help counter wear on the crankshaft driver. Also installed new seals for the water pump.



Crankcases mated and oil pump installed and lines primed.



Water pump impeller installed too. I forgot to grab the crankcase dowels before I left the shop for the holiday, otherwise I would’ve finished the top end tonight.

 

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Grabbed the dowels from work and hung the pistons. Went with some SPI pistons for the 2016+ Axys sled that have the grooves on both sides for longevity. Installed the cylinder as well.



I also sent the head and head cover out to get cleaned because it had some oxidation, and had them strip the paint to mimic the look of the bare head covers on the 2018 engines. Looks pretty sweet! I’m holding off on bolting it on for the moment, as the bolts had major corrosion on them too. I ordered a full set of stainless bolts for the head, water pump, and reed valves.





I’m trying an experiment with some reed valves. The original stock reed cages were damaged with the piston failure. I’m not a fan of the aftermarket reed cages due to the short petal life, but I got a set given to me that fit the older 700/900s. The stuffers needed some minor trimming but otherwise fit the 800 case and intake boot perfectly. I’m changing out the reed petals to the new Axys style petals, which have the Polaris blended material and seem to have great service life. Should help wake up this engine just a hair more.





I also pulled the Quickdrive backing plate from the wrecked parts chassis I had, but it turns out once it was removed that it had been bent in the accident. The ones on eBay weren’t cheap enough to be worth the effort so I just ordered a brand new one through work.

Will update as more parts come in!
 

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Discussion Starter #5
The stainless head bolts came in! Pro Bolt Stainless M8x1.25x55 in case anyone else is interested in using them too.



New O-rings installed:



The head domes were media blasted as well and came out looking nearly new.



Knock sensor torqued and head installed and all stainless bolts in place! Really liking the look here. The water pump and intake boot bolts will possibly be delivered to the shop tomorrow, if not I’ll be picking them up sometime during the week.

 

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My belt drive backer came in! After overlaying it on the one I removed from the parts chassis, it was even more obvious that it was bent.



I thought I had a good Quickdrive jackshaft, but after closer inspection it turns out that the bearing race where it goes through the backer plate was bad.



New ones are close to $400 (and even still spendy at cost), so I scrounged up a chaincase one for free and decided to turn it down into a Quickdrive one. Made a quicky marker with a hose clamp to see how doable this will be.



Chucked it up in the lathe. Already did a rough cut on the tip with a death wheel to get it close to where it needs to be. Faced the end of it to the correct length.



Turned in the factory taper on the splines. Made the angle slightly higher than what the factory did to make it a little easier to slide the sprocket on during belt changes.



Drilled a pilot hole and stepped up to the first bit to thread the end.



Final size



Tapped the end to M10x1.25, added a slight bevel to help guide the bolt.



Side by side to the factory Quickdrive shaft.





Just had to assemble it on the floor!



All there!

 

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great job! I'd love to do a project like this, but the kids and wife take up soooo much time!

Love the job on the head cover. May consider doing that over the summer.
 

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Thank you! I know how that goes too, normally I’d have something like this done in less than a week, but there’s just so many things I have going on. It’s:nuts:

I remodeled my garage over the summer and the last step right now is getting the heater set up, so I can strip the chassis down and make sure the bonding glue cures properly for the chaincase. Should have a stripped down sled here pretty quick once that gets done!
 

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Discussion Starter #10
I will be using the factory Lord 406. The best way to remove it (especially to separate parts) is a propane torch. A scraper tool or wire brush will take it off pretty easily too once heat is applied. There isn’t really much prep other than a clean surface, and scrub it down with soap and water once the old glue is removed.
 

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I get it direct through Polaris since I work at a dealership. Buying just the adhesive itself isn’t that bad, I want to say around $50 over the counter, it’s when they want to sell you the adapter kit along with it that it jumps to a couple hundred bucks. There is a Lord part number in the service manual to order it through online or local places.
 

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The stainless bolts for the waterpump cover and the intake boot finally came in! These ones were from Fastenal, M6x1.0x20 and M6x1.0x25.



Installed the waterpump cover on the short block.



Reed valves all prepped for installation along with new gaskets.



Reed valves and intake boot installed. Came out to be a very nice fit!

 

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Finally making some more progress on this project! I moved a few things out of the garage to make room to tear the sled down.

Getting started





A few minutes later. I had to fight off a few of the fuel tank and seat bolts, so those will all be upgraded to the new square base bolts from the Axys sleds.



A few more things that will need to be addressed. The throttle block is damaged and will be upgraded to the 2013+.



The steering stop area on the overstructure is broken out and will need to be repaired.



Also removed the hardware from the old, damaged side panels and hood.

 

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Track and suspension is off. I’m going to replace the billet wheels with stock ones in the rear and rebuild the shocks while it’s apart.



Front suspension and overstructure coming off next.



Chaincase removed and the area for the new belt drive backer cleaned up. Unfortunately the chassis has a few places that need some welding repair as well as the overstructure, so it will be a little while since they both got sent out for welding.

 

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We are back in business! The chassis now has all the small cracks and issues fixed, the overstructure was repaired also but they missed two places I wanted touched as well, so I won’t have that back until later on.

I brought the chassis inside to keep the bonding glue at a stable temp to cure properly, much to the wifeys displeasure, but spent some time cleaning it beforehand. I’m just about ready to drop on the belt drive backing plate!



 

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i want to see a video of the first start up... and once you're out and about, been interesting seeing all your work on this.
 
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