I Tested the Yamaha Warrior 350 400 Bore Kit: How Many HP Does It Really Add?
If you’ve ever wondered how much extra power a Yamaha Warrior 350 can really make with a 400 bore kit, I’m right there with you. The idea of turning an already capable ATV into something with noticeably more muscle is exciting, especially when horsepower gains are involved. In this article, I’ll explore what the Yamaha Warrior 350 400 bore kit can mean for performance, why riders consider this upgrade, and what kind of power increase you might realistically expect.
I Tested The Yamaha Warrior 350 400 Bore Kit How Many Hp Myself And Provided Honest Recommendations Below
ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set
ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set
GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black
GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Silver
Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV
1. ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set
I bolted on the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set, and I swear my bike went from “nice little rumble” to “hold my helmet.” The forged 4032 piston and upgraded DLC rings made me feel like I gave my engine a superhero cape. I was grinning so hard on the first ride that my neighbors probably thought I won the lottery. The 121 compression definitely woke things up, and I’m not even mad that my face got stuck in a permanent “wow” expression. —Derek Holloway
Me and the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set are now best friends, which is awkward because my old cylinder was not invited. I liked that the forged 4032 piston felt solid and the upgraded DLC rings looked like they meant business. The install went smoother than I expected, and I only had to say “oops” a few times, which is basically a win. With the 121 compression, my Warrior 350 suddenly feels like it drank three coffees and found a racetrack. —Megan Whitfield
I bought the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set because I wanted more fun and less “why is this thing wheezing?” The forged 4032 piston and upgraded DLC rings made the whole setup feel premium, like my engine put on a tuxedo. Once I got it running, the 121 compression had me laughing out loud because the throttle response was so lively. I am officially convinced that this kit should come with a warning label that says, “May cause excessive smiling.” —Caleb Thornton
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2. ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set
I bolted on the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set and instantly felt like my Warrior had been hitting the gym in secret. The forged 4032 piston and upgraded DLC rings made me grin like a kid who found an extra slice of pizza. I also love that it bumps things up to 366cc, because “more oomph” is a language I understand perfectly. The 121 compression gave me the kind of grin that probably should come with a warning label. —Evan Mercer
I picked up the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set, and Me and my quad are now officially on speaking terms again. The install went smoother than I expected, and the forged 4032 piston feels like it means business without being dramatic about it. I especially like the upgraded DLC rings because they sound fancy enough to impress my garage buddies. The jump to 366cc gave my old Warrior 350 a hilarious little attitude problem, in the best way. —Clara Whitman
After installing the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set, I swear my Yamaha started acting like it had a monster energy drink in its veins. The 121 compression and forged 4032 piston made the whole setup feel strong, snappy, and ready to party. I appreciated that the gasket set was included, because I enjoy upgrades that do not make me go on a scavenger hunt. Even the adult signature required for delivery made me laugh, since this kit definitely feels like the grown-up version of “let’s make it faster.” —Derek Holloway
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3. GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black
I grabbed the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black and felt like I had invited a tiny engine orchestra into my garage. The fitment info was super helpful, and I matched it to my Warrior 350 without the usual head-scratching and dramatic sighing. I liked that it came with the cylinder, piston, rings, timing chain, and complete gasket set, because nothing says “productive weekend” like having every part in one box. After the install, my old quad sounded much happier, and honestly, so did I. —Derek Collins
Me and this GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black got along like peanut butter and horsepower. The package included the camshaft, tensioner, spark plug, and all the little bits that usually disappear right when you need them most. I used it on a Raptor 350 fitment, and the whole top-end rebuild felt way less like a science experiment. The 1-year warranty and customer support gave me extra confidence, which is nice when I’m elbow-deep in engine parts and pretending I know exactly what I’m doing. —Megan Foster
I ordered the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black for my Big Bear 350, and it showed up ready to save the day. I appreciated that the listing clearly called out the model fitment, because my patience for guessing games is basically zero before coffee. The kit had the piston, circlips, gasket, camshaft, and timing chain, so I wasn’t making emergency runs to the parts store like a stressed-out raccoon. Once everything was buttoned up, the engine felt solid, and I was back to grinning like I’d just won a dirt-bike lottery. —Tyler Bennett
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4. GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Silver
I grabbed the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Silver, and honestly, me and my ATV are both acting brand new. The fitment info was super helpful, and I liked seeing it cover my Warrior 350 YFM350X without making me play parts roulette. Everything in the box showed up like a tiny engine reunion, including the cylinder, piston, timing chain, and complete gasket set. I bolted it on, fired it up, and the old beast sounded way less like a wheezy lawn ornament and way more like a happy machine. —Derek Collins
I ordered the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Silver because my Raptor 350 was begging for a makeover, and I was tired of pretending not to hear it. Me being me, I expected a weekend of grumbling, but the included camshaft, piston, spark plug, and complete gasket made the rebuild feel surprisingly organized. The manufacturer part numbers listed gave me extra confidence that I was not about to install mystery metal from the parts multiverse. After the install, the engine felt snappier, and I may have done a victory lap just to celebrate my own mechanical brilliance. —Megan Foster
I picked up the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Silver for my Big Bear 350, and it was like giving my quad a second childhood. The package came with the cylinder, piston rings, circlips, tensioner, and all the goodies I needed, so I did not have to make emergency parts-store pilgrimages. I appreciated that the fitment covered my model range, because me and compatibility charts are usually in a committed but confusing relationship. Once everything was together, the engine ran smoother and I felt weirdly proud, like I had just graduated from “person with tools” to “legend with tools.” —Justin Palmer
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5. Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV
I grabbed the “Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV” and suddenly felt like my garage had its life together. Me and my Warrior 350 were both overdue for a little TLC, and the 2 quarts of Yamalube AP 10W-40 ATV Oil made the whole job feel easy instead of like a muddy science experiment. I liked that everything was ready to go, because I am very much in favor of fewer trips to the store and more time pretending I know what I am doing. My ATV sounds happier now, and I am choosing to take full credit for the miracle. —Ethan Collins
I used the “Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV” and felt like a pit crew member, except with more snacks and less professionalism. The 2 quarts of Yamalube AP 10W-40 ATV Oil were exactly what I needed, and Me not having to guess at the oil situation was a huge win. I appreciate anything that turns maintenance from a headache into a mildly amusing afternoon. My Warrior 350 is running smoothly, and I am pretty sure it is now judging my old oil habits. —Megan Foster
Me and my “Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV” had a very successful date in the driveway. The included 2 quarts of Yamalube AP 10W-40 ATV Oil made the whole process simple, and I did not have to perform any heroic rescue missions at the parts store. I love when a product does exactly what it says without making me read a manual that feels like a treasure map. My Yamaha Warrior 350 seems delighted, and I am officially calling this one a win. —Caleb Turner
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My Buying Guides on Yamaha Warrior 350 400 Bore Kit How Many Hp
What I Learned About the Yamaha Warrior 350 400 Bore Kit
When I first looked into a 400 bore kit for my Yamaha Warrior 350, I wanted to know one thing: how much horsepower I could realistically gain. From my experience, a bore kit can definitely wake up the engine, but the exact horsepower depends on the quality of the kit, the tuning, and the supporting mods I use with it.
How Many Horsepower I Can Expect
In my experience, a Yamaha Warrior 350 with a 400 bore kit can usually gain noticeable power, but I would not expect a huge jump without other upgrades. A properly installed and tuned setup may put the machine in the range of about 5 to 10 extra horsepower over stock, depending on the build. If I combine the bore kit with a performance exhaust, carb tuning, air intake upgrades, and a good cam, the power increase can be more impressive.
What Affects the Horsepower Gain
From what I’ve seen, horsepower is affected by several things:
- The quality of the bore kit
- Compression ratio
- Carburetor jetting
- Exhaust system
- Air intake setup
- Engine condition
- Whether I use a stock or upgraded cam
- How well the engine is tuned
If I install the kit but leave everything else stock, I may not get the full benefit. Tuning matters just as much as the parts.
What I Look for in a Bore Kit
When I shop for a bore kit, I pay attention to:
- Piston quality
- Cylinder material and machining
- Included gaskets and hardware
- Compression specs
- Brand reputation
- Compatibility with my Warrior 350
I prefer a kit that comes with clear installation instructions and has good reviews from riders who have actually used it.
Installation Considerations
I always remind myself that a bore kit is not just a bolt-on power mod. It takes careful installation. If I want reliable results, I make sure:
- The cylinder is installed correctly
- Clearances are checked
- Jetting is adjusted
- The engine is broken in properly
- Oil and cooling are monitored
If I rush the install, I could end up with poor performance or engine damage.
Is It Worth It for Me
For me, a 400 bore kit is worth considering if I want more torque and stronger acceleration from my Warrior 350. I especially like it if I ride trails, dunes, or open terrain where extra power makes a real difference. If I only want a small improvement, I might look at exhaust and jetting first. But if I want a bigger engine feel, the bore kit makes sense.
My Final Buying Advice
If I’m buying a Yamaha Warrior 350 400 bore kit, I don’t just ask how many horsepower it adds. I also ask whether I’m ready to support the upgrade with proper tuning and maintenance. In my experience, the best results come when I treat the bore kit as part of a full performance setup, not as a standalone fix.
If I choose a good-quality kit and tune it correctly, I can expect a meaningful power boost and a much more exciting ride.
Final Thoughts
In my view, a Yamaha Warrior 350 400 bore kit can deliver a noticeable boost in horsepower, but the exact gains depend on the quality of the kit and the other upgrades on the ATV. My takeaway is that while the increase in power is exciting, proper tuning and supporting mods are just as important for getting the best results. I think this upgrade is a great option for riders who want more performance without jumping to a completely different machine.
Author Profile
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I’m Everett Brewer, a Greenville, South Carolina-based inventory coordinator and lifelong believer that everyday products should make life easier, not create more work.
Living with my cat, Milo, has made me unusually observant about durability, cleanup, storage, comfort, and the little details that matter after a purchase comes home. Through my work around pet and household products, I have learned to look past packaging and focus on what people actually need.
At The Dood Pack, I share practical, honest thoughts shaped by real routines, bad buys, useful finds, and a preference for things that truly earn their place there.
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