Index
Overview
Tuning
Tuning Overview
Lighter Roller Weights
Remove Variator Restrictor
Stiffer Clutch Springs
Move Needle Jet Washer
Increase Fuel Jet Size
Carb De-restriction
Un-Restricted CDI Unit
Un-Restricted Air Inlet
Trouble Shooting
Compression Test
Fuel Enricher Test
Seized Brake Caliper
General Maintenance
Replace Air Filter
Check & Change Oil
Spark Plug Change
Idle Speed Adjust
Change Brake Pads
Adjust Valve Lash
Electrical
Testing the Battery & Charging System
Battery Change
Coil Change
HT Lead Change
Transmission
Remove Starter Motor
Refurb Bendix Gear
Engine
Camshaft Removal
Valve Removal
Replace Valve Guides
Engine Removal
Return to Transport Listings
Models Covered
Lexmoto, Pulse, Sukida, Baotion, Lifan, Direct Bikes, Huatian, JMStar, QT50, LF50QT, YH50QT,
BT49qt, 139 QMB, Honda, GY6, Motorbike, Taishan, Jonway, Peugeot V-Clic, QT-4, QT-7, QT-9, qt-11, QT-50
Kymco, Tank, Quinqzi, PGO, Roketa, Strada, Vento, Yamati, QMB139, SunL, SYM, QingQi, Volano Plus Many More Chinese Motorcycles, mopeds and
scooters!
Needle Jet Circlip
The needle jet can be found inside the carburetor of your chinese importer 50cc 4 stroke scooter. It looks a little like a
thick needle (hence the name Needle Jet) and it slides up and down inside the motorbikes carburetor as you open and close the throttle, controlling how much fuel is delivered to the engine.
Tuning, Moving the Needle Jet Washer, Imported Chinese Scooter
Applies to: Baotian, Sukida, Hoatian, Lifan, JMStar, Jinlun, Kymco, Tank, Quinqzi, PGO, Roketa, Strada and Taishan QingQi and many more...
To Improve Performance, Move the needle jet circlip
In some cases there is a small circlip at the top of the needle jet that can be moved
up or down. Some manufacturers locate this circlip too low as a way of restricting the performance of the scooters engine. This guide shows you how to check whether your GY6 style 139QMB Import Scooter
is limited in performance by the needle jet circlip.
To gain access to the carburetor of your chinese scooter, you will have to remove the panel under the seat. This will reveal the top of the carburetor. In these pics I have completly removed the carburetor from the bike for clarity,but you do not have to do this:
- Remove the panel under the seat to access the carburetor, you will then see the carburetor. Undo the 2 cross head screws on the top of the carburetor.
- Carefully lift the top off the scooters carburetor (there is a spring under the cover!), take care to note the location of all parts as you remove them.
This will reveal the diaphram and the top of the needle jet. Pull the diaphram, spring, jet and all other parts out carefully.
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Look carefully at the needle jet pin, it should have a washer or circlip at the top, in many cases this washer can be moved up or down. If the circlip is on the lowest setting, as in this pic, then move it up a couple of notches.
- You may have to adjust the idle settings after moving the Needle Jet Pin.
- Reassemble the carburetor on your scooter moped, taking particular care not to damage the diaphram, then test the motorbike to see if it improves top end speed and acceleration.
Notes
Setting the fuel mixtures on any motorbike or moped usually involves a number of factors, if you adjust one, you may well have to adjust the others to balance it out and achieve good running.
If your chinese or taiwanese imported scooter runs badly after you have made tuning changes, return everything to the original OEM settings, then change ONE THING AT A TIME and get it running right, before changing anything else.