EPA engine family

Engine family LJAJC.049S4B

If this code is printed on your emission label, this is your machine's federal record: sold under Jiajue U.S.A. LLC, with an engine built by Zhejiang Jiajue, certified as street-legal scooters and motorcycles.

Displacement: 49cc
Model years: 2020
Models certified: 15
Certificates: 1

What this record says

Sold in the US by: Jiajue U.S.A. LLC
Engine built by: Zhejiang Jiajue
Vehicle category: Highway Motorcycle - Ia (<50cc)
Certificate numbers: LJAJC.049S4B-001

What the number itself says

Reading LJAJC.049S4B left to right: L is the model-year letter for 2020, JAJ is the three-character code the EPA assigned to Jiajue U.S.A. as certificate holder, C marks a highway (street-legal) certification, .049 is the displacement in litres, so 49cc and S4B is Jiajue U.S.A.'s own sequence for that year. Nothing in the number names the factory — that comes from the certificate itself.

The engine, as described on the certificate

The test vehicle Jiajue U.S.A. submitted for this family (model JJ50QT-21) carried engine code JJ1P39QMB. In the Chinese engine-model convention that reads as one cylinder, horizontal (flat) cylinder, with a nominal 39 mm bore, QMB series. Against the certified 49cc that implies a stroke of roughly 41 mm — a sanity check for a piston or cylinder listing, not a published figure.

The certificate describes a four-stroke, single-cylinder engine with 2 valves per cylinder fed by carburettor. There is a catalytic converter in the exhaust, recorded as "TWC, single bed, open loop". The head carries a pulse secondary-air (PAIR) valve.

Rated power on the record is 1.9 kW (about 3 hp) at 7,500 rpm, driving through a CVT (belt and variator).

Engine code on test vehicle: JJ1P39QMB
Nominal bore (from the code): 39 mm · implied stroke ≈ 41 mm
Cylinders / valves: 1 · 2 per cylinder
Cycle: four-stroke
Fuel delivery: carburettor
Oxygen sensor: no
Engine control: other
Catalytic converter: TWC, single bed, open loop
Air injection: PAIR
Rated power: 1.9 kW (≈3 hp)
Rated speed: 7,500 rpm
Transmission: CVT (belt and variator)
Sales area: 49S
Vehicle built by: Zhejiang Jiajue Motorcycle Manufacturing Co.,Ltd
Test vehicle model: JJ50QT-21

Filing history and where it was sold

Jiajue U.S.A. filed one certificate under this family, for model year 2020, sold as 49-state (not certified for sale in California).

The vehicle itself is recorded as built by the same company, Zhejiang Jiajue Motorcycle Manufacturing Co.,Ltd in China — engine and chassis from one source.

Certified emission levels: CO 5.3, HC 0.4 g/km.

What this configuration means when you shop for parts

Jiajue U.S.A. certified the JJ1P39QMB with a carburettor at 49cc, so the fuel-side wear items are the carburettor, its jets and float needle, the intake boot and the choke. The 39 mm bore in the code gives the engine size, not the carburettor size — measure the intake bore and the mounting on the JJ1P39QMB before ordering.

The CVT behind the JJ1P39QMB makes its drive belt, variator rollers and clutch shoes the consumables; belt length and width vary between 49cc machines, so measure the old belt on the JJ50QT-21 rather than ordering by displacement.

The PAIR valve Jiajue U.S.A. lists on the JJ1P39QMB is an emissions part; its hoses perish and are the usual cause of popping on the overrun.

The exhaust on Jiajue U.S.A.'s LJAJC.049S4B carries a catalyst, so a replacement silencer without one changes what the JJ1P39QMB was certified with.

Other records carrying the same engine code

Jiajue U.S.A. certified an engine with this code under 11 other family numbers — the same engine filed again in another year, or in an off-road and a street version:

FJAJC.049S4A (2015)
GJAJC.049S4A (2016)
HJAJC.049S4A (2017)
JJAJC.049S4A (2018)
KJAJC.049S4B (2019)
MJAJC.049S4B (2021)
NJAJC.049S4B (2022)
PJAJC.049S4B (2023)
RJAJC.049S4B (2024)
SJAJC.049S4B (2025)
TJAJC.049S4B (2026)

Other certificate holders whose test vehicle carried the same engine code:

Flywing Motor American Co.,LtdTFMAC.049MCA2026 · different engine factory
Flywing Motor American Co.,LtdSFMAC.049MCA2025 · different engine factory

A shared code from the same factory is a strong search lead. From a different factory it is as often a naming coincidence. Either way it narrows the search; it does not settle it — measure before you buy.

Models certified under LJAJC.049S4B

Every model designation the importer listed on this certificate. If your machine's model name appears here, this is the right record — even if the name on the bodywork is slightly different.

BOLT · Beast · Breeze · Havoc · JJ50QT-13 · JJ50QT-17 · JJ50QT-21 · JJ50QT-22 · JJ50QT-23 · JJ50QT-32 · JJ50QT-40 · JJ50QT-6 · Prime · Scorch · Sprint

Other American badges on engines from the same factory

Related in the registry

Source. US EPA annual certification data — EPA Certified Highway Motorcycle Test Results, MY2006-present; EPA Certified Off-Road Motorcycle / ATV / UTV / Rec Vehicle, MY2006-present. Retrieved 2026-09-07. Full provenance and method.