Since Polaris has suspended the big-block 755 and 900 engines for this season, your choices to build a rockin’ 2007 Polaris mountain sled are based on the potent small-block motors; the 600 H.O. and the all-new Dragon. Problem is, the Dragon 700 was only offered in the spring and was very limited in quantities.
Solution? Turn a 600 H.O. into a fire-breathing Dragon-kicking 727cc. The Polaris engine gurus at Starting Line Products have developed a very reliable and well-mannered big bore kit for the little six, and we’ve spent some time on it carving up the snow in Idaho.
The kit utilizes SLP cylinders to provide enough room for big transfer ports and adequate cooling for no-compromise performance. Basically, the complete kit includes cylinders, head, pistons and rings, wrist pins, power valves and all gaskets. You’ll also need an SLP single pipe exhaust system, SLP Airhorn Intake Kit, Flow-Rite Intake Pre-filters, V-Force reeds and clutching changes to make this thing freakin’ scream.
The result is far more than just Dragon-like power; the 727 Big Bore Kit will bring the output up to 150 HP. Considering the lightweight nature of the RMK and Switchback 600 H.O. models, this much power with this little weight makes the 727 a force to reckon with. It is agile and flickable, with instant and explosive throttle response for a pure-Polaris screamer. We found it to easily be a good match for a Summit 800; not quite as stout down low but with more power than the Rotax on the big end. The large volume ceramic-coated single pipe exhaust provides broad torque and a wide powerband. The large volume canister silencer helps keep noise levels in check, and the ceramic coating stabilizes exhaust temps quickly and reduces underhood heat.
For those who don’t want to spend the bucks for the all-out 727 with new cylinders, we also tested the SLP 660 Big Bore Kit for the Polaris 600 H.O. This kit uses OE cylinders, modified to make room for the larger pistons, with the appropriate porting performed by the SLP wizards whose work is often copied but rarely (if ever) duplicated. While not as wicked as the 727, it provides a very effective performance gain as well for less $$$, making it a great value. Like the 727, the 660 Kit is best matched to an SLP single pipe exhaust system, SLP Airhorn Intake Kit, Flow-Rite Intake Pre-filters, V-Force reeds and clutching changes. Power? 136 HP. Just what you need to run with the bigger cc sleds but with less weight. More importantly the package has stock-like mannerisms in that it has a broad tolerance band – it isn’t peaky or in need of constant tuning to run great.
With either of these kits, SLP provides OE-like specifications for clutching and carburetion requirements for various elevations and temperatures – and they work.
For 2007, Polaris also offers the 600 H.O. with Clean Fire Injection (CFI). SLP is currently working with these new CFI models and they expect to have similar products available for them in the near future. Right now, the kits are fully calibrated for the carbed 2006 & 2007 RMK & Switchback models. The 727 is only offered for high elevation applications, where the 660 can be run anywhere.
And since the 600 H.O. engine packages are in the IQ chassis for the short track models, most all of the RMK mods will now cross over and bolt right into the short track sleds as well. Calibrations for these models are also being finalized, so check on availability for your specific model.
The 727 Big Bore Kit goes for $2612 with new SLP cylinders. The 660 Big Bore Kit (modified OE cylinders, exchange or yours sent in) goes for $1350; the SLP exhaust system, SLP High Flow Intake and V-Force reeds are not required, but highly recommended with this package. Calibration details are provided for both options. For details or to order now so you’re ready when the snow flies contact: Starting Line Products at 208-529-0244, or visit startinglineproducts.com