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Millennium Big Bore Cylinder Kit

(2 reviews)

Item: 386566

$380.97 – $1243.98

Select Your Vehicle - Fitment Guaranteed

Millennium Big Bore Cylinder Kit


  • Just about everything you need to turn your machine into a dirt-eating monster
  • No machining required to complete installation
  • Nickel silicon carbide (NSC) plated cylinders
  • Aluminum cylinder construction
  • 4-stroke pistons are made using a double-bridged forging design
  • Lightweight pistons with the tightest piston-wall clearances in the industry give you a quieter running engine
  • Engineered for maximum performance on big-bore cylinder equipped machines
  • Maximum strength, durability, and power
  • Made in the USA
Specification Details
Bore Varies (make selection above)
Compression Ratio Varies (make selection above)
Country of Origin USA
Displacement Varies (make selection above)
Material Aluminum
Number of Pistons Included Varies (make selection above)
Size Over Standard Varies (make selection above)

Vehicle Fitment


Fitment is guaranteed or your money back plus free return shipping.
Don’t waste time installing a product that doesn't fit. We worked hard ensuring that this product is an exact fit on the vehicles listed below.

Polaris
  • ACE 570 2015-2018
  • ACE 900 SP 2016
  • General 1000 2016
  • RZR 4 800 2011-2014
  • RZR 4 900 2015-2016
  • RZR 570 2012-2021
  • RZR 800 2009-2014
  • RZR 900 2015-2016
  • RZR S 800 2009-2014
  • RZR XP 1000 2014-2016
  • RZR XP 4 1000 2014-2016
  • RZR XP 900 2011-2013
  • Ranger 570 2014-2021
  • Ranger 800 2010-2011, 2013-2014
  • Ranger Crew 570 2014-2018, 2021
  • Ranger Crew 900 2014-2016
  • Ranger XP 900 2013-2016
  • Sportsman 570 2014-2021
  • Sportsman 700 2002-2006
  • Sportsman 800 EFI 2005-2014
  • Sportsman Touring 570 2015-2021
  • Sportsman Touring 570 EFI 2015
  • Sportsman X2 570 2015-2021
Yamaha
  • Grizzly 700 4x4 2007-2017
  • Raptor 700 2013-2017
  • Raptor 700R 2006-2017
  • Rhino 700 FI 4x4 2008-2009, 2011-2013
  • Viking 700 VI 2015-2018

Customer Reviews

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Millennium Big Bore Cylinder

By   on  Verified Purchaser

Good looking product. Haven't installed yet waiting for new head bolts.


Pretty good, not much info available.

By   on 

Ordered this kit winter of 2020/2021 for my 2014 Polaris RZR S 800. Hard to tell difference it has made but it probably makes a little more power by adding 100ccs. I could not find much information or test results. The 85mm pistons are Wossner that are meant for other Polaris quads. The kit will require a fuel controller despite what anyone says. Mine would idle then when warmed up would starve and die. Installed the PC5 and it’s been reliable since. This cylinder is probably overkill for NA applications therefore I intend to turbo it soon. In the meantime nobody has PC5 maps for it, I started with a Bikeman Performance map and since then it’s added a ton of fuel via Autotuner.


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Questions & Answers

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I have a 09 rzr 800 intrested in the 85 mm kit will I need a fuel programmer and what do u recommend d that's plug and plat

Yes, you most likely will need a fuel programmer to make up for the larger displacement. One of the plug and play options we have for that 2009 RZR 800 would be from Wiseco. You can find it by searching for Wiseco Fuel Management Controller.

By Andy
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Any tuning required? I have a 2015 sportsman 570 sp touring and I'm running a big gun fuel programmer and mbrp exhaust will installing the 625cc kit give me issues with my mods?

I have a 2015 sportsman 570 sp touring and I'm running a big gun fuel programmer and mbrp exhaust will installing the 625cc kit give me issues with my mods? Will I have to get the ecu tuned?

I do not believe you would have any problems with installation of that kit with your other mods. You may just want to get a different tune uploaded to your programmer to add some more fuel overall.

By Andy
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