2024 KTM SX65
The updated 2024 SX65 features a new crankshaft, ignition, clutch, and other parts. On the dyno, power is slightly lower than the 2023 model, though it revs a little higher with re-jetting. The 2023 engine remains stronger overall, with known cylinder, power valve, and vibration issues.
The 2024 has increased rotating mass in the crankshaft and clutch, slowing acceleration. In some cases, the 2023 model may still produce more power.
For the longer spark plug required in 2024, you can either modify the head, use a VHM 2023 head with a standard plug, or purchase the long NGK plug in Australia.
2024 Sand Track – Bunbury National Junior MX
Bunbury Sand MX Track in Western Australia is a legendary venue with deep, loose, and fast sandy whoops. It requires sand tyres, long swing arms, and plenty of horsepower. Riders heading to the World Juniors in the Netherlands will be in peak form after racing here.
KTM SX250 2023–24
KTM’s 250 two-stroke continues to be a versatile bike for trail or racing. Performance upgrades include a pipe and head for longer revs, plus an ECU reflash.
⚠️ Engine note: Piston-to-conrod clearance is tight - over-revving or incorrect assembly can cause damage.
How to Race/Ride Cheap
- Prevent dirt or water from entering the engine.
- Change transmission oil regularly.
- Recheck bolts and parts that loosen due to vibration.
- Maintain your chain properly (WD-40 then chain lube).
- Ensure clutch freeplay to avoid burnout.
- Avoid unnecessary engine mods until the rider is skilled.
- Buy consumables in bulk.
2023 KTM SX125 Electronic Fuel Injection
The first EFI 125 from KTM reduces top-end power compared to the 2022 carb model but adds midrange. Performance can be improved with a better pipe, cylinder head, ignition mapping, and fueling calibration. Expect refinements in 2024–25.
Synthetic, Caster Oils & Ratios
- Synthetic oils: Best for modern engines. Clean-burning options like Penrite Ester Synthetic and Silkolene Comp 2 work well for learners.
- Ratios: Smaller engines now use 60:1 successfully.
- Caster oils: Smell great but leave sticky deposits and can separate in fuel. Only use if you clean regularly and refresh fuel often.
Porting of Modern Cylinders
Modern port designs favor airflow speed over size. Grinding without dyno testing often worsens performance. Correct porting of windows and exhausts can yield gains but requires expertise and lubrication methods to preserve chrome plating.
Spark Plugs
High-performance engines need stronger plugs to handle vibration and detonation. Recommended:
NGK BR9ECM or BR9ECMIX (Iridium).
NGK R6918B-9 for most 85cc+ two-strokes ($60 each).
⚠️ Always use the specified plug type—cheaper alternatives can damage the engine.
Summer vs Winter Jetting
Summer vs Winter Jetting
Crankshaft Balance
Different engine sizes require different balance factors, which directly affect power delivery.
Fuels
VP Roo Fuel lowers combustion temps and works well in 2-strokes (requires 6% richer jetting and higher compression). Fuels above 100 octane provide no benefit.
Mazzocchi Forks
Some SX65 pistons lack a wear band-ring - fit one from the rebound side for smoother performance. Use only Mazzocchi seals for minimal drag.
Engine Cryogenic Treatment
Wear resistance
Heat dissipation
Consistent compression
Overall performance (HP, torque, revs)
Reduced warping/cracking
SX150 Setup
HGS exhaust
VHM cylinder head
185–190 main jet
Ignition timing: 1.1mm BTDC
Exhaust Choices
Scalvini: Strong top-end but fragile and easily damaged.
Van Hasselt: Best midrange and durable.
HGS: Strongest top-end but requires tuning.
USA Pipes: Crack often; Euro pipes are stronger but rust.
SX150 Setup
HGS exhaust
VHM cylinder head
185–190 main jet
Ignition timing: 1.1mm BTDC
Mazzocchi Forks
Some SX65 pistons lack a wear band-ring—fit one from the rebound side for smoother performance. Use only Mazzocchi seals for minimal drag.
Scalvini Exhausts
High-end Italian pipes that add significant power but are fragile and expensive.
EHR HGS Exhausts
Consistent build quality and strong performance across production runs.
EHR Products
Dyno-tested race parts that widen the powerband, making bikes easier to ride and race.
High Performance Super Finishing (Gearbox Gear Tumbling)
Gear treatment for lower friction and smoother shifting. Provided by H.P.S.F, Victoria.
Pistons: Types, Changes & Replacement
OEM and aftermarket pistons differ in weight/height.
VHM billet pistons feature a run-in coating.
Replace pistons at 10–20 hours (dyno tests show power drops after 12 hours).
Never fit a new silencer before a race—power may drop temporarily.
Always replace cylinder head O-rings and exhaust O-rings with piston changes.
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