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!
50cc Valves Overview
As with any 4 stroke engine, your 50cc chinese honda clone scooter has valves and valve springs which open and close to allow fuel/air
mix into the cylinder and exhaust gases out. Over time, wear and heat can reduce the valves ability to seal properly giving your engine lower compression and possible running problems.
This page tells you how to remove, inspect and replace the valves and springs on your chinese import motorcycle or scooter.
Steps to Remove and Inspect Valves, QMB139 Clone 50cc
Applies to: Baotian, Sukida, Hoatian, Lifan, JMStar, Jinlun, Kymco, Tank, Quinqzi, PGO, Roketa, Strada and Taishan QingQi and many more...
Valve Removal
As always, this page can only give an overview of how to remove the valves and springs from your chinese scooter clone, some import scooters may differ from these instructions. These instuctions assume that you have already removed
the camshaft and cam gear from your scooter. If you have not already done so, see Camshaft Removal for a step by step guide.
- Remove the camshaft from your clone chinese scooter. (refer to Camshaft Removal.)
- Pull the cylinder head upwards and off the cylinder head bolts to remove. This may take some effort as you will have to break the gasket seal.
- Use a Valve Spring Compressor to remove the collet and release the spring and components. Take care to note in which order you take the spring components off.
- Check each valve to see if it is bent, burnt or broken. Measure the outer diameter of the valve stem, change the valve if the stem measures less than 4.9mm.
- Check the springs for breaks or weakness, replace if necessary.
- Whilst you have the valves out it is a good idea to inspect and measure the valve guides, ream any debree from the valve guide and measure the internal diameter. If the internal diameter is greater than 5.3mm, replace the valve guide.
- If the valves look burnt or worn, either replace or use grinding paste to re-seat the valves correctly. If you do this you will need to adjust the valve clearances.
- Refitting is the reverse procedure. Clean any old head gasket material from the cylinder head mating surfaces and use a new cylinder head gasket.
Notes
Poor running, particularily at idle and burning oil (blue smoke) are symtoms of valve and valve guide wear. If you find grinding and replacing valves daunting, you can always remove the cylinder head and take it to a specialist engineering firm to do the work for you.
Imported scooters, mopeds and motorcycles, particularily those from china (chinese) are often constructed from inferior materials and metal parts wear out much quicker.