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Big Bore Cylinder Kit versus Standard Cylinder Kits

Big Bore Cylinder Kit versus Standard Cylinder Kits
August 17, 2015 14392 Views 4 comments

Standard Bore Cylinder Kits

Standard bore kits are OEM replacements for your machine when your cylinder has worn out. Standard bore kits follow the specifications set out by the manufacturer and are exact replacements for the OEM parts, with the exception of aftermarket replacement parts that may use a stronger material for more durability. Also, standard bore kits do not offer any performance upgrades such as more speed or more torque.

Big Bore Cylinder Kits

In contrast, a big bore cylinder kit gives enhanced performance through power. More specifically, “when you increase the cylinder’s bore you increase the surface area on top of the piston…” which “… spreads the fuel/air mixtures workload and produces more power…” (Motocross Action Magazine). This means that increasing the bore size can increase the horsepower by increasing the engine displacement (Motocross Action Magazine). This is because cubic capacity is determined by the bore and stroke (Dickson). It’s easy to see the appeal of a big bore kit for both the racer and the casual ATV enthusiast.

How do they compare?

Let’s compare two parts to explore the difference between standard bore and big bore kits. For instance, the Honda 400EX cylinder below has the factory bore and stroke of 85.00 mm x 70.00 mm with a cylinder displacement 397cc. This is a standard OEM replacement for the Honda 400 EX with no performance upgrade.

Niche Industries Honda 400EX CylinderNiche Industries Honda 400EX Cylinder ~ MSRP $340.52 USD. Save up to 33% at Partdiscounter.com. Click on the picture to see more.

In contrast, the Niche Industries 440cc Big Bore Cylinder Kit below has a cylinder bore and stroke of 89.00 mm x 70.00 mm. This is an increase of 4 mm on the bore which creates a cylinder displacement of 440cc, increasing the displacement by 43cc more than the standard bore, without increasing the stroke. This modification would give the quad enhanced performance and more horsepower.

Niche Industries 440cc Big Bore Cylinder Kit for the Honda 400EXNiche Industries 440cc Big Bore Cylinder Kit for the Honda 400EX ~ MSRP $397.22 USD. Save up to 23% at Partdiscounter.com. Click on the picture to see more.

Curious to know more about the Niche Industries 440cc Big Bore Cylinder Kit for the Honda 400EX? Watch the video above for more information.


While big bore kits are an attractive upgrade, it should be noted that not all big bore kits are the same, so results can vary (Cassandra). Be sure to do your research to find the right kit for your quad. Also, there is a “tipping point…” where “… the bore gets too big for the length of the stroke…” and loses rpms. (Motocross Action Magazine).

However, a big bore kit can give significant “increase in torque”, making it a worthwhile modification despite the cost and time (Cassandra). Which do you prefer: big bore kits or standard cylinder kits? Let us know in the comments!

Looking for big bore kits, standard cylinder kits, and other parts? See more at Partdiscounter.com


“MXA Wrench Tech: The Ins and Outs of Big Bore Engines.” Motocross Action Magazine. Hi-Torque Publications, Inc., 21 November, 2013. Web. 10 August, 2015.

Dickson, Tim. “Understanding Bore and Stroke”. Visordown. Immediate Media Company Ltd., 5 November, 2010. Web. 10, August, 2015.

Cassandra. “Power Up Your 4x4.” Outdoor Life. Bonnier Corporation, n.d. Web. 11 August, 2015.

Steve. Likar December 20, 2015 at 8:43 PM
I need a top end for a TTR 90. Please help
The kit for pw 80 was great
PartDiscounter.com December 21, 2015 at 11:22 AM
Hi Steve,
We're happy to hear that you liked the PW80 top end kit. Unfortunately, we do not carry a top end kit for the TTR 90 at the moment.
Dan S June 17, 2018 at 3:00 PM
Why does the Raptor 660R 686cc Big Bore Cylinder & Piston Kit cost less than the Standard Bore Cylinder & Piston Kit?
Jenn June 18, 2018 at 11:18 AM
Hi Dan S,
Thank-you for your comment. Our prices are updated regularly to stay competitive in the current market.