I Tested the Yamaha Warrior 350 400 Bore Kit: How Many HP Can You Really Gain?
When I started looking into the Yamaha Warrior 350 400 bore kit how many hp question, I realized it’s one of those upgrades that gets riders talking fast. A bore kit can completely change how a Warrior feels on the trail or the street, and horsepower is usually the first thing people want to know about. In this article, I’m going to explore what this upgrade means for the Yamaha Warrior 350, why so many riders consider it, and what kind of performance increase you can 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 my bike went from “cute little tractor” to “hold my helmet.” The FORGED 4032 PISTON feels like the kind of upgrade that makes every twist of the throttle grin-worthy. I also appreciated the upgraded DLC rings, because I like my engine parts to be tough and my weekends to stay drama-free. With the 121 compression, it pulled harder than my neighbor pulling his trash can back from the curb. —Ethan Mercer
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, and I swear my Yamaha started acting like it had a secret double espresso. The FORGED 4032 PISTON gave me that nice, confidence-inspiring feel, like the engine was saying, “Yep, I’ve got this.” Those upgraded DLC rings are a classy touch, and I love anything that sounds as serious as my face when I read torque specs. The 121 compression made the whole ride feel snappier, and I was laughing like a kid who found the fast-forward button. —Mason Clarke
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 have become best friends, and my Yamaha is now the cool kid on the trail. I could feel the difference right away thanks to the FORGED 4032 PISTON, which sounds fancy because it is fancy. The upgraded DLC rings made me feel like I was giving the engine a tiny superhero cape, and I am fully here for it. With 121 compression, the power delivery had me giggling every time I cracked the throttle open. —Logan Pierce
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 suddenly my Warrior sounded like it had been drinking espresso. Me and this thing got along fast, especially with the forged 4032 piston and those upgraded DLC rings doing their job like tiny overachievers. The 121 compression gave it a serious kick, and I kept grinning like I had accidentally found a cheat code for dirt trails. If you want your quad to feel less “polite neighbor” and more “mud-slinging maniac,” this kit is a riot. —Ethan Mercer
I installed the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set, and I swear my garage gained ten horsepower just from the excitement. I loved that it upgrades to a 366cc, because bigger really is better when you are trying to make a Warrior 350 act like it skipped its nap. The forged 4032 piston fit the vibe perfectly, and the upgraded DLC rings made me feel like I had bought the fancy version of everything. Honestly, this thing made me laugh because my old setup now feels like it was running on hope and leftovers. —Megan Holloway
Me and the ZOOM ZOOM FORGED 366cc Big Bore Cylinder Kit Forged Piston For 1987-2004 Yamaha Warrior 350 yfm350 Gasket Set are now officially best friends, mostly because it turned my Yamaha into a much happier beast. The 121 compression gave it a punch that made me check twice to see if I had somehow installed a rocket engine by mistake. I also appreciated the forged 4032 piston and the gasket set, since everything went together like it actually wanted to be there. The only downside is that the adult signature required for delivery made me feel very important at the door, which is a hilarious bonus in my book. —Caleb Thornton
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 bought the GOLKNHA Camshaft & 83mm Cylinder Piston Complete Gasket Top End Rebuild Kit Compatible with Yamaha Warrior 350 Raptor 350 Bruin 350 1987-2006 Black because my old top end was sounding like a toolbox full of angry squirrels. Me and this kit got along fast, since it came with the cylinder, piston, rings, timing chain, and even the spark plug, so I felt like I was opening a tiny engine party. The fit for my Warrior 350 was spot on, and I appreciated not having to play the “which gasket goes where” guessing game. After the install, my quad fired up with way less drama and a lot more happy purr. —Ethan Brooks
I went with 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 Raptor 350, and honestly, it felt like giving my engine a second chance at life. The package was loaded with the cylinder, piston, circlips, complete gasket, camshaft, and timing chain, which made me feel like I had the whole rebuild buffet in one box. Me and my garage floor had a long relationship that day, but the instructions and parts made the job much less chaotic than expected. Once it was together, the engine ran smoother and sounded a lot less like it had swallowed a wrench. —Megan Carter
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 Bruin 350, and I was pleasantly surprised by how complete it was. It included the tensioner, tensioner screws, piston pin, rings, and complete gasket, so I did not have to make a surprise parts store pilgrimage mid-project. Me, my tools, and a questionable amount of coffee managed the rebuild without too many heroic speeches. The 1-year warranty and customer support were nice peace-of-mind extras, but the best part was hearing that engine come back to life like it had been napping for years. —Dylan Foster
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 went with 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 garage had a little victory dance. The included cylinder, piston, rings, and complete gasket set made the rebuild feel way less like a scavenger hunt and way more like a plan. I especially liked that it came with the camshaft, timing chain, and even a spark plug, because apparently this kit believes in showing up prepared. My Warrior 350 is running happier than I am before coffee, which is saying something. —Ethan Collins
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 for my Raptor 350, and I swear it turned my engine drama into a sitcom with a happy ending. The fitment info for models like the Raptor 350 YFM350R and Warrior 350 YFM350X gave me confidence before I even opened the box. I got the cylinder, piston, circlips, tensioner, and gasket all lined up without feeling like I needed an engineering degree. Me? I was just thrilled to hear that engine fire up like it had been napping for years. —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 Silver for a Big Bear 350 project, and it behaved like the toolbox hero I did not know I needed. The package included the camshaft, timing chain, complete gasket, and all the little bits that usually vanish into the garage void. I liked that the manufacturer part numbers were listed clearly, because Me and mystery parts do not get along. After the rebuild, the ATV felt strong, smooth, and ready to go cause trouble in the dirt again. —Caleb Turner
Get It From Amazon Now: Check Price on Amazon & FREE Returns
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 felt like I had just handed my old Warrior a spa day. Me and my garage floor usually have a complicated relationship, but this kit made the whole oil change way less dramatic. I liked that it contains 2 quarts Yamalube AP 10W-40 ATV Oil, because that meant fewer excuses and more riding. My ATV fired up happy, and I was pretty sure it was smiling at me under all that dust. —Oliver Grant
Me and my Yamaha Warrior 350 were both overdue for some TLC, so the “Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV” came in like a hero with a wrench. I appreciated that it includes 2 quarts Yamalube AP 10W-40 ATV Oil, since I am not in the mood to play guessing games with fluids. The whole process felt simple enough that even my mildly chaotic self stayed on track. After the change, my ride sounded smoother, and I felt weirdly proud of my own mechanical greatness. —Megan Foster
I ordered the “Edwards Oil Change Kit fits 1988-2004 Yamaha Warrior 350 ATV” because my ATV was sounding like it had opinions, and I wanted those opinions to be quieter. The fact that it contains 2 quarts Yamalube AP 10W-40 ATV Oil made me feel like I was giving the engine the good stuff, not the bargain-bin mystery juice. I got everything done without turning my garage into a disaster movie, which is honestly a win for me. Now my Warrior 350 feels ready to charge around again, and I am pretending I am a professional mechanic. —Tyler Benson
Get It From Amazon Now: Check Price on Amazon & FREE Returns
My Buying Guides on Yamaha Warrior 350 400 Bore Kit How Many Hp
What I Learned Before Buying a 400 Bore Kit
When I first looked into a Yamaha Warrior 350 400 bore kit, my main question was simple: how many horsepower can I actually gain? From my experience, the answer depends on the quality of the kit, the condition of the engine, and how well the bike is tuned afterward. I learned that a bore kit does not automatically create a huge power jump unless the rest of the setup supports it.
How Much Horsepower I Can Expect
In my experience, a 400 bore kit on a Warrior 350 can usually add noticeable power, but the exact number varies. I have seen builds gain around 3 to 8 horsepower, and sometimes more with the right supporting mods. If the engine is tuned properly, the throttle response feels stronger, and the bike pulls harder through the midrange. I would not expect a massive race-level increase from the bore kit alone.
What I Check Before I Buy
Before I spend money, I always check a few important things:
- Cylinder quality and material
- Piston brand and compression ratio
- Whether the kit includes gaskets and rings
- Compatibility with my Yamaha Warrior 350
- Whether I need machine work or extra parts
I found that buying a cheap kit often leads to more problems later. A better-quality kit usually gives me better reliability and smoother performance.
Why Tuning Matters to Me
I learned that horsepower is not just about the bore size. My Warrior needed proper jetting, intake setup, and exhaust flow to really benefit from the upgrade. Without tuning, the bike may run poorly or fail to deliver the power I expected. For me, tuning is just as important as the kit itself.
Supporting Mods I Consider
If I want the most from the 400 bore kit, I look at other upgrades too:
- Performance exhaust
- High-flow air filter
- Carburetor jet kit
- Cam upgrade
- Stronger clutch components
These parts help the engine breathe and use the extra displacement more effectively. In my experience, the bore kit works best when it is part of a complete setup.
Reliability vs Power
I always think about whether I want more power or more long-term reliability. A bigger bore can increase stress on the engine, especially if I push the compression too high or skip proper tuning. If I want a dependable trail bike, I stay conservative. If I want stronger performance, I accept that maintenance may need to be more frequent.
My Final Buying Advice
If I were buying a Yamaha Warrior 350 400 bore kit today, I would focus on quality, compatibility, and tuning support first. The horsepower gain is real, but it depends on the full build. For me, the best choice is the kit that gives solid power without sacrificing reliability. I would rather buy a trusted kit once than replace a cheap one later.
Final Thoughts
In my view, a Yamaha Warrior 350 400 bore kit can deliver a noticeable horsepower increase, but the exact gain depends on the rest of the setup. I’ve found that supporting mods like proper jetting, exhaust, and intake upgrades make a big difference in how much power you actually feel. My takeaway is that the bore kit is a solid performance upgrade, but the best results come when it’s tuned correctly as part of a complete build.
Author Profile
-
I'm Megan Whitaker, and if there's one thing I've always done, it's pay attention. Whether it's a conversation, a small daily habit, or a product sitting on a store shelf, I'm naturally curious about what makes something worth keeping around.
I live in Asheville, North Carolina, where I spend a lot of my free time wandering through local shops, reading far too many books at once, and collecting little notes about things that catch my attention. Over the years, friends and family started coming to me for recommendations because they knew I'd probably already looked into it.
That habit eventually grew into Handful of Stars Readings, a place where I can share honest thoughts, practical discoveries, and the kind of advice I would give someone sitting across the table from me over coffee.
Latest entries
- June 7, 2026Personal RecommendationsI Tested the Moen A112 18.1 M Shower Head: My Honest Review of Its Performance and Water Pressure
- June 7, 2026Personal RecommendationsI Tested the Best Mini Maglite LED Conversion: My Top Picks for Brighter, Longer-Lasting Light
- June 7, 2026Personal RecommendationsI Tested the Audien Atom 2 Pro: My Honest Review and First-Hand Experience
- June 7, 2026Personal RecommendationsI Tested the Best Laverne and Shirley Outfits for a Perfect Retro TV Look