What $20K in a Yamaha Raptor 700 Big Bore Build Actually Looks Like

The Raptor was originally built by Trinity Racing — so it was already not a stock machine when Steve got his hands on it. That didn't stop someone from showing up in the comments to point out that it wouldn't need rebuilding if it were a Honda. Classic. Steve's response was more or less that Trinity built the thing, and that as he's gotten heavier over the years, his horsepower requirements have gone up proportionally. Losing weight would technically be cheaper. That was never the plan.

Steve's Yamaha Raptor 700 big bore build didn't happen overnight. This is one of those machines where every major system got touched — bottom end, top end, head, clutch, ignition, brakes, wheels. The kind of build where you stop adding up receipts somewhere around the $15K mark and just keep going.

The Raptor 700 is already a solid sport quad out of the box. Yamaha's 686cc single thumper makes decent power for trail riding and light dunes. But "decent" wasn't the plan here. Steve wanted something closer to a race-prepped machine that could still be ridden on weekends without a support truck following behind.

Warming an aluminum engine case to around 250°F before pressing in bearings isn't a hack — it's the right way to do it. The aluminum expands just enough that the bearings seat cleanly without having to beat them in. The tool of choice for this operation was Steve's kitchen oven. He did have two proper powder coat ovens in the garage, but they still needed to be welded together and wired up, so they weren't exactly an option. The kitchen oven worked. It was only in there about ten minutes. Steve cleaned the oven after. His wife found out anyway.

Here's everything Steve rattled off when Scott asked what's in it. This isn't a bolt-on intake and call it a day — this is a ground-up engine build with supporting mods everywhere it matters.

• Brand new engine — not a rebuild, a fresh case-up assembly
• 4mm stroker crankshaft — adds stroke length for more displacement and low-end torque
• 2mm big bore JE piston — bumps total displacement to 720cc
• Megacycle stage 4 cams — aggressive cam profile for top-end power
• Coal Shed Racing high velocity full ported head — hand-ported for maximum airflow
• 1mm oversized stainless steel valves — bigger valves to match the ported head
• Heavy duty valve springs — required for the aggressive cam profile
• Titanium retainers — lighter retainers let the valves follow the cam at higher RPM
• Decomp billet bolts — because a 720cc thumper needs all the decompression help it can get

When Steve posted the open engine cases with a caption about waiting on his +4mm stroker crank, not everyone in his orbit knew what they were looking at. Some thought "stroker" was funny for reasons that had nothing to do with engine displacement. Steve clarified it was the inside of an ATV engine. Nobody was confused after that. Nobody's sense of humor was any worse for wear either.

• billet clutch basket — stock baskets notch and cause grabby engagement under hard use
• Heavy duty clutch — handles the extra torque without slipping

• Custom ECU — tuned for the bigger displacement, cam timing, and airflow
• High current coil — hotter spark for more complete combustion
• 10mm spark plug wire — low-resistance wire to deliver the coil's output cleanly

• Brand new black beadlock wheels — beadlocks keep the tire seated under hard cornering and low PSI
• YFZ450 calipers — a common Raptor upgrade for better stopping power

A stock Raptor 700 puts down somewhere around 45-48 horsepower at the wheel. Steve's build is estimated at 72-74hp — that's roughly a 55% increase over stock. For a sport quad that weighs around 420 pounds dry, that power-to-weight ratio puts it in serious territory.

For context, a stock YFZ450R — Yamaha's dedicated race quad — makes about 40hp. This Raptor makes nearly double that, in a chassis designed for a much milder engine. The heavy duty clutch, billet basket, and upgraded brakes aren't just nice-to-haves at this power level. They're mandatory.

This is the reality of building anything past the bolt-on stage. A stroker crank alone runs $400-600. A JE piston kit is another $250-350. Head porting from a shop like Coal Shed Racing can easily be $800-1,200. Megacycle stage 4 cams are around $300-400. Custom ECU tuning is another $500-800. And that's just the engine — add the clutch work, ignition upgrades, beadlocks, and YFZ calipers and you see how $20K adds up fast.

The asking price of ~$8,500 for the complete machine means someone's getting a built Raptor for less than half what went into it. That's how it always goes with builds — you never get your money back, but the next owner gets a machine they could never afford to build from scratch.

Steve's not selling because anything's wrong with the Raptor. He's selling because he's got a BMW that needs a Ford 8.8 rear end swap, and machines cost money. That's how it works in a garage full of projects — something's always funding the next thing.

Scott's half-joking deposit request tells you everything about the machine — when someone in the crew who's seen it run in person wants first dibs, that's a better endorsement than any dyno sheet.

Steve's Yamaha Raptor 700 big bore build is what happens when you stop modifying a quad and start building one. A 720cc stroker with a ported head, stage 4 cams, and a custom ECU pushing 72-74hp is serious hardware. At $8,500 for a machine with $20K in documented parts, someone's getting a deal that doesn't come around often. If you're in the market for a built Raptor and you're not afraid of what 74 horsepower feels like on 420 pounds, this is the one.