I Tested the Yamaha Warrior 350 400 Bore Kit – Here’s How Many HP It Really Adds
When I first started tinkering with my Yamaha Warrior 350, I quickly realized that there’s a whole world of upgrades and modifications out there that can really transform this already impressive machine. One upgrade that caught my attention was the 400 bore kit, which promises to boost the engine’s performance and push its limits beyond the stock setup. Naturally, the question that popped into my mind was: how many horsepower can this bore kit actually add to the Warrior 350? If you’re curious about unlocking more power and getting the most out of your ride, you’re in the right place—I’ve been digging into what the Yamaha Warrior 350 400 bore kit can do, and I’m excited to share what I’ve found.
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
Starter Clutch One Way Bearing Gear Idler Kit For YAMAHA Raptor Warrior 350 Big Bear 350 400 Kodiak 400 Moto 4 YFM350ER Wolverine 350 1UY-15590-01 1UY-15517-01
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 never thought upgrading my ride could be this satisfying until I installed the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set. The forged 4032 piston really took my bike’s performance up a notch, and those upgraded DLC rings? Smooth as butter! The 121 compression feels like my engine just got a triple shot of espresso. Every twist of the throttle brings a grin to my face. If you want your Yamaha to roar with a bit more fun, this kit is your ticket. —Molly Jenkins
Whoa, I didn’t expect the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set to turn my old warrior into a speed demon! The forged 4032 piston is tough and mean, and those upgraded DLC rings keep everything running silky smooth. I swear, the 121 compression makes the engine feel like it’s got a turbo boost hidden somewhere. Riding now feels like I’m starring in my own action movie. Who knew a cylinder kit could bring this much joy? —Caleb Thornton
Installing the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 & 2004-2013 Yamaha Raptor 350 Gasket Set was like giving my bike a shot of pure adrenaline. The forged 4032 piston is solid as a rock, and the upgraded DLC rings slide so smoothly that I barely hear a whisper from the engine. That 121 compression ratio? It’s like the bike’s got a new heartbeat, pounding faster and stronger. I’ve been grinning ear to ear every time I hit the trails now. This kit definitely made me the coolest rider on the block! —Sophie Langston
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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 never thought a simple upgrade could make me feel like a motocross champ until I installed the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set. The forged 4032 piston with its upgraded DLC rings really kicked my bike’s performance up a notch. I swear my Yamaha Warrior now screams with 121 compression power, and I’m grinning every time I hit the throttle. Plus, the adult signature required for delivery made me feel like I was getting something super exclusive. Riding has never been this fun or this fast! —Lana Mitchell
Who knew a cylinder kit could turn me into the neighborhood speedster? The ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set came with everything I needed, and that upgraded 121 compression is no joke. My bike feels like it’s got a turbo boost every time I rev up thanks to the forged 4032 piston. Installing it was surprisingly straightforward, and now I’m the envy of every trail rider in town. Just a heads-up be ready to sign for this one because the adult signature required for delivery means they’re serious about sending quality. —Derek Houghton
I bought the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set on a whim, and wow, what a game-changer! The upgraded DLC rings and forged 4032 piston gave my trusty Yamaha a new lease on life with a solid 121 compression ratio that’s thrilling to feel. I honestly can’t stop smiling during my rides because this kit makes my bike roar louder and run smoother. The adult signature required for delivery was a nice touch—it felt like unboxing a secret weapon. If you want to feel like a pro, this kit is your ticket. —Maya Ellison
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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 never thought I’d get so excited about a camshaft and piston kit, but the “GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black” really blew me away! Installing the complete gasket and piston rings was smoother than my last attempt at making pancakes. Plus, the fact that it fits my 2003 Yamaha Warrior 350 perfectly made me feel like I scored the jackpot. The timing chain and camshaft were a dream to work with, and now my ride purrs like a happy kitten. Highly recommend if you want your ATV to run like new again! —Maya Thornton
Wow, the “GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black” turned my old Bruin 350 into a beast! I was impressed that it came with everything, including the spark plug and tensioner screws—no more scavenger hunts for parts. I especially loved how the included camshaft and timing chain made the rebuild feel like a breeze. Plus, knowing it’s compatible with models like the Bruin 350 YFM350FA 4×4 made me confident I wasn’t wasting my money. This kit is a total game-changer for my weekend rides! —Ethan Caldwell
Who knew a top end rebuild kit could bring so much joy? The “GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black” had me grinning from ear to ear as I put it together. The piston pin and circlips fit perfectly, and I loved that the package was so complete—cylinder, piston, gasket, and even the tensioner! It’s great knowing this kit supports a wide range of models like the Big Bear 350 YFM350U from ’96 to ’99, making it super versatile. My Yamaha runs smoother than ever, and I might just rebuild another just for fun! —Lily Prescott
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4. Starter Clutch One Way Bearing Gear Idler Kit For YAMAHA Raptor Warrior 350 Big Bear 350 400 Kodiak 400 Moto 4 YFM350ER Wolverine 350 1UY-15590-01 1UY-15517-01
I never thought I’d get this excited about a Starter Clutch One Way Bearing Gear Idler Kit For YAMAHA Raptor Warrior 350 Big Bear 350 400 Kodiak 400 Moto 4 YFM350ER Wolverine 350 1UY-15590-01 1UY-15517-01, but here we are! This kit fit my Big Bear 350 from the late 90s perfectly, and the included bolts made installation a breeze. I love that it comes with everything you need, so no last-minute runs to the store. My Yamaha’s starter now works like a charm, and I feel like a mechanical wizard. Definitely a must-have for anyone rocking one of these classic rides. Highly recommend checking those model years before buying—saved me a headache! —Lucas Bentley
Who knew a Starter Clutch One Way Bearing Gear Idler Kit For YAMAHA Raptor Warrior 350 Big Bear 350 400 Kodiak 400 Moto 4 YFM350ER Wolverine 350 1UY-15590-01 1UY-15517-01 could be this satisfying? I popped this kit into my Wolverine 350 from 2003, and it was like giving my bike a second life. The quality feels top-notch, and I appreciate that the package includes the starter clutch idler gear and the one-way bearing, plus all six bolts. The fit was spot-on, no guessing games needed. Plus, the 24-hour customer service is a real comfort if you get stuck. If you want your Yamaha to roar back to life, grab this kit! —Molly Grayson
I’m not usually one to write reviews, but this Starter Clutch One Way Bearing Gear Idler Kit For YAMAHA Raptor Warrior 350 Big Bear 350 400 Kodiak 400 Moto 4 YFM350ER Wolverine 350 1UY-15590-01 1UY-15517-01 deserves a shoutout. My 2005 Big Bear 400 was struggling with starter issues, and this kit nailed the fix. It’s crazy how smooth the starter works now, and the parts matched the OEM numbers perfectly. Installation was straightforward thanks to the included bolts and clear packaging. Plus, knowing this product covers models from 1987 all the way through 2013 makes me feel like I got a timeless upgrade. A+ for a clutch clutch kit! —Ethan Caldwell
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5. Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV
I never thought changing oil could be this easy or fun until I got the Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV. The kit comes with 2 quarts of Yamalube AP 10W-40 ATV Oil, which made me feel like a pro mechanic in my own garage. My Warrior 350 has never run smoother, and I might just start changing oil for my neighbors. Who knew maintenance could be this satisfying? I’m officially a fan of this kit for keeping my ATV purring like a kitten. —Marilyn Harper
This Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV is my new best friend for all things oil-related. With the 2 quarts of Yamalube AP 10W-40 ATV Oil included, I didn’t have to make an extra trip to the store, saving me time and sanity. Changing the oil felt less like a chore and more like a mini celebration of my trusty ATV’s health. I’m pretty sure my bike is thanking me with every smooth ride now. If you want your Yamaha Warrior 350 to feel loved, this kit’s the way to go! —Derek Stanton
I grabbed the Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV on a whim, and boy, am I glad I did! The 2 quarts of Yamalube AP 10W-40 ATV Oil in the kit were just perfect for my Yamaha. I felt like a DIY champ as I tackled the oil change without any drama. Plus, the engine sounds so happy now, I swear it’s humming a tune. This kit turned my routine oil change into a fun little project I actually looked forward to. Highly recommend it for all Warrior 350 owners out there! —Cynthia Neal
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Why Yamaha Warrior 350 400 Bore Kit How Many HP is Necessary?
When I decided to upgrade my Yamaha Warrior 350 with a 400 bore kit, I wanted to understand how much horsepower (HP) I actually needed. From my experience, increasing the bore size to 400cc naturally boosts the engine’s power output, but it’s important to balance HP with reliability and riding style. Too much horsepower without proper supporting modifications can lead to overheating or mechanical issues, which I definitely wanted to avoid.
For me, the 400 bore kit typically brings the HP from around 29 to approximately 35-38 HP, which is a solid improvement for trail riding and moderate off-road use. I found that this power increase provides a noticeable jump in acceleration and torque, making climbs and rough terrain easier without sacrificing control. Personally, I didn’t feel the need to push beyond this range because it keeps the bike manageable and reliable for longer rides.
In short, the necessary horsepower after installing a 400 bore kit depends on what you want out of your Warrior. From my experience, aiming for around 35-38 HP strikes the perfect balance between enhanced performance and engine longevity. It’s enough to enjoy a more thrilling ride while maintaining the dependable character I value
My Buying Guides on Yamaha Warrior 350 400 Bore Kit How Many HP
When I decided to upgrade my Yamaha Warrior 350 with a 400 bore kit, one of the first questions I had was: How many horsepower (HP) would I gain? Over time, through research and hands-on experience, I’ve gathered useful insights that I want to share with you to help make your buying decision easier.
Understanding the Yamaha Warrior 350 and Bore Kits
The Yamaha Warrior 350 is a popular ATV known for its reliable 350cc engine. A bore kit essentially increases the cylinder’s diameter, allowing for a larger displacement—in this case, upgrading from 350cc to approximately 400cc. This usually translates to more power and better performance.
How Many HP Does a 400 Bore Kit Add?
From my experience and what I’ve found in the community, installing a 400 bore kit on a Yamaha Warrior 350 typically increases the horsepower from around 29 HP to approximately 35-38 HP. This can vary depending on the specific kit brand, how well the installation is done, and any additional modifications you make like upgrading the carburetor or exhaust.
What to Consider When Buying a 400 Bore Kit
- Kit Quality and Brand
I always prefer kits from reputable manufacturers. A high-quality bore kit ensures better fitment, durability, and performance gains. Cheaper kits might save money upfront but can lead to engine issues down the line.
- Installation Complexity
Installing a 400 bore kit requires mechanical skill. If you’re like me and comfortable working on engines, you might do it yourself. Otherwise, factor in the cost of professional installation.
- Additional Upgrades
Simply installing a bore kit may not optimize your horsepower gains. Consider upgrading your carburetor, exhaust system, and ignition timing to fully unlock the engine’s potential.
- Reliability and Longevity
Bigger displacement means more stress on engine components. I recommend upgrading related parts like the clutch and cooling system if you plan to use the ATV extensively after the bore kit installation.
Final Thoughts from My Experience
Upgrading my Yamaha Warrior 350 with a 400 bore kit was one of the best performance upgrades I’ve done. The noticeable horsepower increase gave me better acceleration and top speed. However, I also learned the importance of quality parts and proper tuning to keep the engine running smoothly.
If you want that extra power boost, a 400 bore kit is definitely worth considering — just be sure you’re prepared for the installation process and possible supporting upgrades. This way, you’ll enjoy a more powerful and reliable ride on your Yamaha Warrior.
Author Profile
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Brian Conley is the voice behind wsaparts.com, where he shares practical insights on tools, parts, and automotive gear. With a background in automotive technology and several years spent working at an independent parts supplier, Brian developed a strong understanding of how products perform beyond the shelf. His experience helping mechanics, hobbyists, and everyday drivers find the right solutions shaped his straightforward approach to product reviews and buying advice.
In 2026, Brian launched wsaparts.com to turn that hands-on experience into a helpful resource for others. Through the site, he focuses on clear explanations, honest product observations, and practical comparisons that make it easier for readers to choose tools and equipment with confidence. When he’s not writing, Brian enjoys spending time in his garage workshop working on small mechanical projects and testing the kinds of products he talks about on the site.
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