Nibbi PWK24 vs Mikuni VM26
Engine output on a stand — there is no drivetrain and no chassis in these numbers, which is the same basis Harbor Freight rates the engine on. Simulated at 800 ft and 75°F; thinner air makes less power and wants less fuel, so both the horsepower and the jet move with them. Governor removed. Compression 9.06:1.
Where each one wins
| RPM | Nibbi PWK24 | Mikuni VM26 | diff |
|---|---|---|---|
| 1500 | 2.83 | 3.00 | +0.18 |
| 2000 | 3.88 | 4.13 | +0.24 |
| 2500 | 4.99 | 5.30 | +0.31 |
| 3000 | 6.13 | 6.51 | +0.38 |
| 3500 | 7.36 | 7.82 | +0.46 |
| 4000 | 8.73 | 9.28 | +0.54 |
| 4500 | 10.19 | 10.81 | +0.62 |
| 5000 | 11.72 | 12.29 | +0.57 |
| 5500 | 13.29 | 13.72 | +0.44 |
| 6000 | 14.17 | 14.80 | +0.63 |
Horsepower at each rpm. Everything except the part named is identical between the two runs.
Two flat slides at the top of the range, four millimetres apart, on an engine built to use them.
The larger carb wins on peak, which is what a larger carb usually does. What it does not do is come on any earlier, and on a smaller build a 26mm can be more carburettor than the engine can fill.
Match the carb to the cam and the pipe. A race carb on a mild engine is a tuning problem you paid extra for.
The build
| Engine | Predator 212 Hemi (Gen 2) — 27/25mm valves · 5.5mm stems |
|---|---|
| Governor | Governor removed (full rev range) |
| Piston | Stock flat top — Hemi OEM (ARC DJ-1285PH · .550" CH) |
| Head | Stock Hemi head — as-cast factory |
| Head gasket | Stock HEMI — fiber .045" (ARC DJ-1310TP) |
| Camshaft | DynoCams 335 — .334" · 259.8/264.7 @.050 · 36 lb · 8,500-9,000 rpm |
| Valve springs | 34-36 lb open/race |
| Retainers | Billet w/ keepers, 36 lb — ARC DJ-1046 ($11.00) |
| Valves | Stainless kit, Hemi 27/25mm — GPS KDVALKIT27-25 · ARC DJ-SSVALVE HKT |
| Rocker arms | Stock rocker arm — 1:1 ratio |
| Connecting rod | ARC 6256 Billet — Hemi (+.020" raises CR) |
| Flywheel | ARC 6696 Billet — Hemi Speedway (32° BTDC) |
| Ignition coil | ARC rev limiter coil — 9,000 rpm |
| Carburetor | Nibbi PWK24 — 24mm flat slide |
| Air filter | Pod / cone filter — GPS / OMB angled filter kit |
| Exhaust | DynoCams race exhaust pipe |
| Fuel | Pump 87 octane |
The other one
| Engine | Predator 212 Hemi (Gen 2) — 27/25mm valves · 5.5mm stems |
|---|---|
| Governor | Governor removed (full rev range) |
| Piston | Stock flat top — Hemi OEM (ARC DJ-1285PH · .550" CH) |
| Head | Stock Hemi head — as-cast factory |
| Head gasket | Stock HEMI — fiber .045" (ARC DJ-1310TP) |
| Camshaft | DynoCams 335 — .334" · 259.8/264.7 @.050 · 36 lb · 8,500-9,000 rpm |
| Valve springs | 34-36 lb open/race |
| Retainers | Billet w/ keepers, 36 lb — ARC DJ-1046 ($11.00) |
| Valves | Stainless kit, Hemi 27/25mm — GPS KDVALKIT27-25 · ARC DJ-SSVALVE HKT |
| Rocker arms | Stock rocker arm — 1:1 ratio |
| Connecting rod | ARC 6256 Billet — Hemi (+.020" raises CR) |
| Flywheel | ARC 6696 Billet — Hemi Speedway (32° BTDC) |
| Ignition coil | ARC rev limiter coil — 9,000 rpm |
| Carburetor | Mikuni VM26 flat slide — race engines |
| Air filter | Pod / cone filter — GPS / OMB angled filter kit |
| Exhaust | DynoCams race exhaust pipe |
| Fuel | Pump 87 octane |