21XZ-R Speed Engine
The 21XZ-R advantage: more time from every tank!
In the pits, time is the enemy and O.S. 21XZ-R can defeat it. They can run a full 10-minute heat on just one tank of fuel, while most other engines require two. That puts you a pit stop ahead of the pack and in sole possession of the lead to the checkered flag.
Construction Features
- A 1-piece crankcase and 21M slide-valve carb for smoother transitions and higher top-end speeds.
- Redesigned 21M carburetor for improved fuel economy.
- Silicone-filled crankshaft is balanced with tungsten weights for optimum balance and minimum vibration.
- Crankshaft also features a DLC (Diamond-Like Carbon) coating for reduced friction and enhanced performance.
- ABC cylinder liner with 7 scavenger ports and three exhaust ports for maximum combustion and timing efficiency.
- Lightened, machined piston to reduce rotating mass, with a balanced knife-edge conrod and DLC-coated piston pin to further reduce wear.
The 21XZ-R's outer head has been lightened, and moved down on the crankcase. It's a design refinement that lowers CG to improve stability, while maintaining the cooling power of higher CG heads.
- Specifications
- Parts Listing
- Accessories
Stock Number: OSMG2041
Displacement: 0.212 cu in (3.49 cc)
Bore: 0.640 in (16.27 mm)
Stroke: 0.661 (16.8 mm)
Practical rpm: 4,000-45,000
Output: 2.76 hp @ 33,000
Weight: 12.1 oz (343 g)
Includes: RP7 Turbo glow plug, exhaust seal ring, 0.01 & 0.02 mm cylinder head gaskets, 9 mm (red) carb restrictor, flywheel collet & exhaust, carb and fuel nipple dust caps
Displacement: 0.212 cu in (3.49 cc)
Bore: 0.640 in (16.27 mm)
Stroke: 0.661 (16.8 mm)
Practical rpm: 4,000-45,000
Output: 2.76 hp @ 33,000
Weight: 12.1 oz (343 g)
Includes: RP7 Turbo glow plug, exhaust seal ring, 0.01 & 0.02 mm cylinder head gaskets, 9 mm (red) carb restrictor, flywheel collet & exhaust, carb and fuel nipple dust caps
Primary Accessories
| Stock Number | Mfr Number | Product Description | Quantity Needed |
| ODOP3320 | ODOP3320 | O'Donnell 20% Racing Quart | 1 |
Field Equipment
| Stock Number | Mfr Number | Product Description | Quantity Needed |
| DTXP0310 | DTXP0310 | Duratrax Ultimate Glo-Starter C | 1 |
| HCAP2550 | HCAP2550 | Hobbico 4-Way Wrench w/Plug Storage | 1 |
| OSMG2360 | 72413000 | O.S. Super 203 Air Cleaner Assembly | 1 |
Optional Accessories
| Stock Number | Mfr Number | Product Description | Quantity Needed |
| DTXP0315 | DTXP0315 | Duratrax Ultimate Glo-Starter D | 1 |
| DTXP0320 | DTXP0320 | Duratrax Ultra Slim AA Glow Starter | 1 |
| DTXP3000 | DTXP3000 | Duratrax Rapid Heat Glo-Starter w/Charger | 1 |
| DTXP5701 | DTXP5701 | Duratrax 1/10 & 1/8 Universal Starter Box | 1 |
| DTXR0185 | DTXR0185 | Duratrax Engine Tuning Screwdriver | 1 |
| DTXR0187 | DTXR0187 | Duratrax Engine Tuning Tool | 1 |
| HCAP3001 | HCAP3001 | Hobbico After Run Engine Oil 2 Fl Oz | 1 |
| OSMG2393 | 72413200 | O.S. 203 Filter Elements (4) | 1 |
| OSMG2702 | 72106440 | O.S. M2000SC Exhaust Manifold | 1 |
| OSMG2939 | 72106130 | O.S. T-2060SC WN Tuned Pipe | 1 |
| OSMG2961 | 72106042 | O.S. Joint Spring T-2040 | 1 |
| OSMG5673 | 22826140 | O.S. Exhaust Gasket 21RZ | 1 |
| OSMR2976 | 71521000 | O.S. Long Socket Wrench With Plug Grip | 1 |
| OSMR2977 | 71520100 | O.S. Speed Plug Wrench | 1 |
| OSMR4000 | 71415300 | O.S. Speed Clutch Wrench & Adjuster | 1 |
| OSMR4001 | 71415200 | O.S. Speed Flywheel Key | 1 |
