Between 2-stroke and 4-stroke dirt bikes, the 2-stroke is the lighter and cheaper full-size motocross bike in both Yamaha's and KTM's 2027 lineups, and its engine breathes through a reed valve instead of a camshaft and poppet valves. The 4-stroke costs $1,000 or more extra and weighs a little more, but Yamaha's 4-strokes add fuel injection and smartphone engine tuning.
| 2027 Yamaha model | Engine | Wet weight | Starting MSRP |
|---|
| YZ125 | 125cc 2-stroke | 212 lb | $7,199 |
| YZ250 | 249cc 2-stroke | 227 lb | $8,099 |
| YZ250F | 250cc 4-stroke | 236 lb | $9,099 |
| YZ450F | 450cc 4-stroke | 243 lb | $10,299 |
Figures were read from Yamaha's website on 12 October 2026. Yamaha's wet weight includes all fluids and a full tank of fuel. Starting MSRP is the Team Yamaha Blue edition and excludes tax, title, license, registration, prep, dealer-installed options and the $675 destination charge.
Published manufacturer data and Searchshop dealer listings are the basis of this comparison, not test rides. Yamaha and KTM were chosen because both sell a 250cc-class 2-stroke and a 250cc 4-stroke motocross bike in the same model year, so the engine type is the main difference between each pair.
Specifications and prices come from Yamaha's and KTM's own websites, read on 12 October 2026. Yamaha quotes weight with a full tank and KTM quotes weight without fuel, so weights are compared within each brand, never across brands. Dealer asking prices come from new listings on Searchshop on the same day.
A 2-stroke dirt bike engine in these lineups draws in its mixture through a reed valve, while the 4-stroke uses overhead camshafts and four valves. Yamaha's specification pages show the difference plainly:
- The 2027 YZ250 is a "249cc liquid-cooled 2-stroke; reed-valve inducted" engine fed by a Keihin PWK38S carburetor, with a compression ratio of 8.9 to 10.6:1.
- The 2027 YZ250F is a "250cc liquid-cooled DOHC 4-stroke; 4 valves" engine with 44mm Mikuni fuel injection and a 14.1:1 compression ratio.
- Both have a five-speed gearbox. The YZ125 has six speeds.
Carburetors are not a rule for 2-strokes. KTM's 2027 250 SX 2-stroke uses Keihin electronic fuel injection with a 39mm throttle body, and KTM's model page says you "press the starter button" to start it.
Lubrication is the other big difference. KTM's 2022 SX technical data lists "mixture oil lubrication" for its 2-strokes, at 1:40 for the 125 SX and 1:60 for the 250 SX, meaning oil is mixed into the fuel. Its 4-strokes use pressure lubrication with two oil pumps. Check the owner's manual for the exact model year you buy.
The 2-stroke is lighter than the 4-stroke of the same class in both brands' 2027 lineups. Yamaha lists the YZ250 at 227 lb wet and the YZ250F at 236 lb wet, a 9 lb difference. The YZ125 is lighter still at 212 lb.
KTM lists the 250 SX at 99.4 kg without fuel and the 250 SX-F at 101.5 kg without fuel, a 2.1 kg (about 4.6 lb) difference. Tank capacity is about 7.2 liters on both.
The 2-stroke has the lower list price in both brands. Yamaha's 2027 YZ250 starts at $8,099 and the YZ250F at $9,099, a $1,000 gap. KTM's 2027 250 SX has a base MSRP of $9,649 and the 250 SX-F $10,699, a $1,050 gap, plus $690 freight on each.
Dealer asking prices on Searchshop follow the same order. The table below covers new 2026 model-year Yamaha listings on 12 October 2026, all editions combined. Counts are listings whose title matched the model name.
| New 2026 Yamaha | Engine | Listings (dealers) | Median asking price |
|---|
| YZ125 | 2-stroke | 15 (6) | $7,399 |
| YZ250 | 2-stroke | 12 (3) | $8,099 |
| YZ250F | 4-stroke | 29 (6) | $8,899 |
| YZ450F | 4-stroke | 38 (7) | $10,299 |
The samples come from a small number of dealers, so treat the medians as a guide to what dealers are asking, not a market average. Asking prices exclude taxes and fees. Compare 2-stroke and 4-stroke dirt bikes for sale on Searchshop to see current dealer prices near you.
Yamaha's 4-stroke motocross bikes add smartphone engine tuning that its 2-strokes do not list. Yamaha says its Power Tuner app lets YZ250F owners "adjust air/fuel mixture and ignition timing." On the YZ450F, the app also covers traction and launch control tuning and a lap timer.
Yamaha's 2-strokes stay with a carburetor, but not every 2-stroke does. KTM's 2027 250 SX has fuel injection and a starter button, so compare the exact models rather than assuming every 2-stroke lacks electronics.
The right choice depends on whether a lower price and weight, or fuel injection and tuning, matter more to you. Compare the specific models before you decide.
- Lowest price and lowest weight: a 2-stroke such as the Yamaha YZ250 or KTM 250 SX costs at least $1,000 less new than the matching 4-stroke and is lighter on each brand's scale.
- No fuel mixing and app tuning: a 4-stroke such as the Yamaha YZ250F or KTM 250 SX-F; KTM's technical data lists pressure lubrication for its 4-strokes and premix for its 2-strokes, and Yamaha's 4-strokes add smartphone tuning.
- Fuel injection and push-button starting on a 2-stroke: look at KTM's 2027 250 SX.
- A lighter, smaller race bike: the YZ125 is the lightest full-size bike in Yamaha's table above.
Before you buy a used bike of either type, work through the used motorcycle buying guide, and plan upkeep with the motorcycle maintenance guide. New riders can start with the motorcycle buying guide. When you are ready to shop, browse dirt bikes and motorcycles for sale on Searchshop and ask each dealer for an out-the-door price.
Shoppers comparing the two engine types often ask these questions.
Yes, a 2-stroke dirt bike has the lower list price in both Yamaha's and KTM's 2027 motocross lineups. The Yamaha YZ250 starts at $8,099 against $9,099 for the YZ250F, and the KTM 250 SX is $9,649 against $10,699 for the 250 SX-F. Destination or freight charges are extra on all four.
Yes, KTM's 2-stroke motocross bikes have used fuel premixed with oil. KTM's 2022 SX technical data lists a 1:40 mixture for the 125 SX and 1:60 for the 250 SX, while its 4-strokes use pressure lubrication with two oil pumps. Ratios can change by model year, so follow the owner's manual for your bike.
Yes, Yamaha's 2027 YZ125 2-stroke is lighter than its 2027 YZ250F 4-stroke. Yamaha lists the YZ125 at 212 lb and the YZ250F at 236 lb, both wet with a full tank of fuel. The YZ125 also has the lower starting MSRP, $7,199 against $9,099.
No, motocross bikes such as KTM's SX models are built for the track. KTM's price notes for the 2027 250 SX and 250 SX-F say "closed-course competition use only." If you need to ride on public roads, look for a model the manufacturer sells as street legal or dual-sport.
Manufacturer pages were read on 12 October 2026.
