High Compression Polaris RZR XP 900 Race Build

August 1, 2018 / by Kevin Bailey

Keith Reid is a dedicated racer in the modern world of UTV racing. He currently races a RZR XP 900, that was recently rebuilt to add more power and reliability. Read on as we take a look inside Keith's engine, powered by JE pistons.

It’s no secret that UTVs have taken four-wheel off-road racing by storm over the last decade. People started building Yamaha Rhinos more for performance than for utility, then Polaris released the RZR 800, then 900, then 1000, creating a legacy of success in the UTV market while simultaneously fueling a growing form of off-road racing.

Keith got hooked on UTV racing. But with racing, comes a lot of work!

Keith Reid of Team Johnson Racing is one person who found himself hooked on the behind-the-wheel thrill of UTV racing. He started racing in 2016 in a bone-stock RZR XP900. His first race was the GBC Motorsports Heartland Challenge in Carlisle, LA, which is a 4-hour, night-time endurance race. He placed 4th in his class and 15th overall with no official racing experience and no aftermarket equipment, fueling his passion to continue racing UTVs.

He continued racing in 2017 in everything from local events to GNCC XC3 class, but did not have as much luck, experiencing mechanical failures in more than one instance. His most recent failure was testing at a local track, where a valve dropped, damaging his piston, cylinder, and cylinder head.

So, the rebuild process began, but this time with some upgrades. Keith recruited help from one of his sponsors, Power Sports Nation, to get set up with the components he needed to keep him stay competitive. We got a chance to chat with Keith about the specifics of this side-by-side build.

After the failure Keith had, he knew it would be best to tear down the top and bottom end and perform a complete rebuild.

What were the most common problems you encountered when racing the stock car? Were there any engine issues or power complaints?

Reid: A lot of the common problems were just getting the machine set up the way I wanted and just getting everything fixed up.  The motor that was in the RZR was what we called “the junkyard dog.”  That motor had parts and pieces from about 3 or 4 different motors from years past, but for the most part the machine ran great!  When you’re in a 900, you always have some complaints about power since you’re racing 1000cc RZRs and turbo machines, and you just don’t have enough power to run them down in a straight away. But when it comes down to driving in the woods, the 900 holds its own very well.

How did the stock pistons look when you pulled them out? And the cylinders before they were replated?

Reid: The mag side piston was completely destroyed because that was the side that the valve dropped. That, in turn, scarred up the cylinders very badly.  Unfortunately, I did not get any pictures of the pistons or cylinders when I pulled everything apart.  The blunt of the damage was in the head, which I had to send off because of major, major damage.

Keith bumped up the compression with a 12.5:1 JE piston to get some extra power out of the 900.

Keith’s rebuild included an all-new crank, counter balance shaft, rod bearings, and high compression JE pistons. According to Reid, he’s always trusted JE for his dirt bike pistons, so he wanted to run them in his RZR as well. The piston set he chose bumped the compression up to 12.5:1.

In the head, Keith chose stage 2 Hotcams for a little extra grunt, complemented with Weller Racing head studs to make sure everything stays where it needs to be. Keith is estimating over 90 horsepower all said and done with this build.

How does the power difference feel when driving it after the rebuild?

Reid: The power difference is pretty noticeable!  With the higher compression (JE) pistons and the cams I installed, you can feel a lot more of the low-end grunt that machine has.  I’m still working on some clutching, but this machine runs amazing right now!

High compression pistons and more aggressive camshafts gave the RZR a noticeable power increase and bottom end hit.

What kind of fuel do you run with the new, higher compression pistons?

Reid: As of right now I am just running 91 octane pump gas.  I have a Power Commander Auto Tuner on the machine right now to make sure my tuning is spot on, then I plan on making the switch to VP fuels 110 octane 50/50 mixture with the 91 octane.

Keith made sure he'd keep building compression without any issues by checking and set his ring end gap. Ring gap is a critical aspect of piston operation, so be sure it's at the recommended spec.

What kind of tuning changes have you made with the rebuild?

Reid: We have had to make a lot of changes to the tune.  After we fired it up and drove it around, we found out that the car was way too rich and we had to make some timing changes.  We’re still tinkering with the tune, trying to get her dialed in perfect.

Are there any other key modifications you’ve made outside of the engine?

Reid: Definitely!  I was running a stock set of Exit Shocks, and they were just sprung and valved way too soft for how I like the car to handle.  I ended up sending my shocks to one of the #1 guys that does suspension for GNCC racers like Cody Miller, Hunter Miller, Tim Farr, and a lot of other professional racers.  George White at E2R hooked me up with a great set-up and I couldn’t be any happier.  I’ve made a sway bar change, clutching changes, wheel and tire changes, and exhaust to help the machine out as well!

je_pistons_rzr_900-8Keith started his 2018 race season with the Iowa ATV and SxS Hare Scramble Series (IATVHSS), racing the open/1000 in his freshly built RZR XP 900. Keith would like to give a special thanks to everyone helping him out this race season: JE Pistons, Power Sports Nation, The Farm MX, Team Johnson Racing, E2R ( Double E Racing ) , GBC Motorsports, Nutz Graphics, Hotcams, Weller Racing, Firecoat Custom Powder Coating, Hite Trucking LLC, and Guy Ware with Mac Tools.

Topics: ENGINE BUILDS, featured, Powersports

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