Chung Yang / Zenoah -
General information

Chung Yang engines
Engine instruction
Cleaning jobs/problem shooting
Mix ratio

Which differences have Chung Yang engines?
Model  CY 225 R 230 R 260 R 260 W R 260PTD R 270 R 290 L 290 GP420 GP460
Cooling Air Water Air
Engine cc 22,5 22,5 25,4 25,4 25,4 26,9 28,5 28,5 41,5 45,7
Bore mm 32 32 34 34 34 35 36 36 40 42
Stroke mm 28 28 28 28 28 28 28 28 33 33
Power HP / RPM 0,9 / 7500 2,2 / 11500 2,6 / 11500 4,0 / 13500 2,2 / 12000 2,7 / 11000 2,9 / 11000 2,3 / 10000 4,0 / 11000 4,3 / 11000
Torque Nm / RPM/min 0,95 / 5500 1,45 / 9500 1,51 / 9500 1,91 / 10500 1,35 / 9000 1,57 / 9250 1,63 / 9250 1,75 / 7500 3,3 / 8000 3,22 / 9000
max. RPM RPM/min 11000 19500 19000 21000 12000 18000 18000 16000 18000 18000
Application   6,2 9,2 9,5 9,5 9,5 9,5 9,5 9,5 8,8 9,2
Oil / Gasoline Mix     1/25
Carburetor   WYJ Walbro WT Walbro HDA
Spark Plug    NGK BMP6A NGK CMR7H
Clutch Start to open at RPM 4000 5900 5700
Open at RPM 5500 8000 7300
Engine Size L in mm 159 168 168 175   168 168 168 277 186
B in mm 232 150 150 155   150 150 150 244,5 277
H in mm 218 197 197 203   197 197 197 228 228
Weight Kg 2,5 2,56 2,56 1,7   2,56 2,56 2,56 3,76 3,76

Engine instruction 23cc, 26cc, 29cc Zenoah and Chung Yung engines

On the Chung Yang und Zenoahn Engines with standard air filter including factory oiled filter insert. This filter is sufficient for the use on tracks with low formation of dust. To be on the safe side we recommend to change or rather clean the foam filter inserts and oil them with the filter oil 040507

1. Fuel
For the correct fuel mixture we recommend to use Super Plus fuel together with a high-quality 2stroke oil Castrol Power 1 Racing Oil 010429 The mix ratio of the fuel ought to be around 1:25.
See the mix ratio
Do not store fuel mixtures longer than 4-6 weeks as afterwards certain components of the mixture may decompose. This could cause a reduction of the lubricating effect which results in higher wear and less power. First fill the oil into the canister, then the fuel.

2. Initial operation of the engine
Before each starting up of the engine check the air filter on dirt and correct and firm seating. Test the engine for leaks at manifold, cylinder foot and carburetor-insulator area. Should the engine be slightly greasy or damp we recommend to replace the gasket. The basic adjustment of the engine is preset by the factory. You can adjustment the Walbro Carb when you tuned your Chung Yung ore Zenoah Engine.
Hier Link zur Walbro Einstellung Seite

3. Starting the cold engine
Close the carburetor throttle valve and bring it into neutral position. Now shut the choke flap at the Walbro carburetor or air filter (Zenoah G230/G260RC and Chung Yang). Press the primer pump at the carburetor until it is filled with fuel. Pull the rope starter slowly until you feel the first resistance, then pull strongly until the engine ignites audible. Normally the engine will die down again after the initial start. Now open the choke flap and pull the rope starter once again until the engine runs.

4. Starting the warm engine
Keep the choke flap open, press the primer pump until it is filled with fuel and actuate the rope starter. To turn the engine off, press the stop button until the engine stops.

5. Carburetor adjustment
The carburetor adjustment is preset by the factory according to the local conditions. Depending on air filter, exhaust silencer and usage site a correction may be necessary. Operate the engine until it has reached its working temperature. If the engine decelerates a little during the acceleration, then it runs too lean. In this case turn the no-load adjusting screw L (1/8 rotation) anticlockwise. If the engine revs up only slowly stammering and under clouds of smoke, then the engine probably runs with an overrich mixture. In that case turn the no-load adjusting screw L (1/8 rotation) clockwise. In order to adjust the maximum range of speed, lift the rear wheels and operate the engine under hot running conditions shortly at full speed. Now you can turn the full-load adjusting screw H to the left (if the mixture is too lean) or to the right (overrich mixture).
ATTENTION! Operate the engine under no-load conditions only shortly at the maximum speed range. In most cases the no-load adjusting screw has to be readjusted if the adjustments of the engine were modified.


6. Basic adjustment of the carburetor
The declared values are reference values. In some cases a re-adjusting may be necessary. If you have the feeling that the adjusting screws L or H are completely misadjusted, then close both adjusting screws carefully in clockwise direction. Afterwards open both adjusting screws L and H around 1,25 – 1,5 rotations anticlockwise.
Avoid maximum speed ranges under no-load conditions during the first two tank fillings and with a cold engine, also longer full-speed drives.
Never operate the engine in closed rooms without sufficient ventilation. Further safety instructions are enclosed with the engines.

Starting of an overriched engine
If you realize already when starting that the engine or the piston blocks, then the spark plug has to be taken out. Dry the wet spark plug with the flame of a lighter or of a small gas burner. Bring the engine in neutral position (carburetor closed) and pull the rope repeatedly without mounted spark plug. Screw in the hot spark plug, plug on the socket and pull the rope without the choke. If the spark plug appears wet again, remove the fuel pipe from the carburetor and seal it. Then repeat the above described procedure. After the engine has started, let it run shortly, then switch it off and attach the fuel pipe at the carburetor again. Then start the engine as usual.

Cleaning jobs at the Zenoah and Chung Yang Engines
If you drive the models mostly off-road we recommend to control the air filter after each fill-up. If you still can see the oiled foam surface all-over the complete outline, the air filter foam can be used furthermore.
If the surface is covered with a dirt film the foam filter has to be exchanged. Rinse the foam filter with washing-up liquid (always from inside to outside), let it dry, check it on fissures and lubricate it with oil again. The most simple way to lubricate the foam filter is to seal the boring of the foam filter with your thumb and fill it completely with air filter oil 040507. Then press the foam carefully together until the whole foam is completely drenched in oil. Remove surplus oil through kneading with a tissue or a cloth.
After rides on grass it’s imperative to demount the engine housing of the cylinder in order to remove the grass between the cylinder cooling fins. If you don’t follow this instruction there may be the risk that not enough cooling air can circulate around the cylinder. This can lead to a significant loss of power or even to a jamming of the piston. In order to make the cleaning procedure easier without dismounting the engine the guiding rails at the engine housing can be removed. To take the engine housing off just remove the 2 fixing screws.
Control the starter housing too if in-coming grass surrounds the starter housing. The ventilation openings of the starter housing have to be completely cleansed to make sure that enough cooling air can be ingested again.
After rides under wet conditions f. e. rain or after cleaning the model with water we recommend to detach the clutch and free the fixing screws as well as the clutch blocks from water. Otherwise it could be possible that fretting corrosion occurs which affects the correct function of the clutch. It has turned out as helpful to lubricate the fixing screws slightly with copper paste (do not use too much paste, otherwise grease may get on the clutch blocks).

Sooting of the spark plug:
If you drive your model over a longer period only very slow this may result in a sooting of the spark plug. The consequences are spark failures, as the case may be the engine can not be started anymore. Combustion residues occur at the bottom of the insulator. The ignition voltage is now transmitted over the conductive soot film to the ground at the plug thread, but without the desired ignition spark (therefore very small or weak ignition spark). In this case we recommend to lift the rear wheels of the model and speed up to full throttle repeatedly for a few moments. This secures that the soot residues are combusted again according to the arising higher temperature. Possibly the spark plug has to be unscrewed and cleaned (see picture). In that case proceed as follows: Unscrew the spark plug and press the spark plug socket on the spark plug. Hold the outside thread of the spark plug with a bared flat pliers against the cylinder and activate the engine with the rope. Now you should be able to see an ignition spark clearly at the spark plug. If no ignition spark is visible and the annular passage is still highly sooted we recommend to remove the sedimented oil carbon (sooting) between insulator and housing with a steel needle. Then rinse the annular passage with FG Cleaning Spray and let it air. Mount the spark plug back in the engine and start it.
Afterwards operate the engine a few seconds at full throttle so that the spark plug is cleaned. For the further use of the engine please see to a correct carburetor adjustment. Don’t adjust the engine too rich as then the same problem may occur again (see instruction 5. carburetor adjustments). If you operate your model often at low throttle we also recommend to use the FG spark plug 07343/06. This spark plug has a higher heat range and therefore it reduces the sooting.

Engine has spark failures or no ignition spark:
Checking connection between spark plug and spark plug Cab. The candle plug must tightly sit on the spark plug. If this should not be the case, spark plug plug NGK CR7HIX Iridium exchanging for a new one.010511

Increased and irregular idle speed:
The engine has an irregular increased idle speed. Furthermore it’s very difficult or rather impossible to adjust the carburetor. In that case we recommend to check the condition of insulator and carburetor gasket, exchange defective parts if necessary.

Mix ratio
Motor Type Producer Engine Power Octane Mix ratio
G23LH Zenoah 22.5cc 1,2 PS 95 Octan or more 40:1
G2D Zenoah 22.5cc 2.0 PS 95 Octan or more 40:1
G230RC Zenoah 22.5 cc 2,8 PS 95 Octan or more 25:1
G260RC Zenoah 25.4cc 3.0 PS 95 Octan or more 25:1
GZ25N14 Zenoah 25.4cc 1,4 PS 95 Octan or more 40:1
GZ25N23 Zenoah 25.4cc 1,5 PS 95 Octan or more 40:1
G43L Zenoah 41.5cc 2,5 PS 95 Octan or more 40:1
Tuned G43L Zenoah 41.5cc 3,5 PS 95 Octan or more 30:1
G62PU Zenoah 61.5cc 5,0 PS 95 Octan or more 25:1
CY23RC Chung Yang 22.5cc 2,5 PS 95 Octan or more 25:1
CY26RC Chung Yang 25.4cc 3,0 PS 95 Octan or more 25:1
CY27RC Chung Yang 26.9cc 3,25 PS 95 Octan or more 25:1
CY29RC Chung Yang 28.9cc 3,5 PS 95 Octan or more 25:1
GP290 Chung Yang 28.5cc 3,25 PS 95 Octan or more 25:1
GP420 Chung Yang 41.5cc 4,2 - 5,2 PS* 95 Octan or more 25:1
GP460 Chung Yang 45,8cc 4,5 - 5,5 PS* 95 Octan or more 25:1
GPL290 Chung Yang 28.9cc 2,5 PS 95 Octan or more 25:1

mixture 1:20 1:25 1:30 1:35 1:40 1:45 1:50
Gasoline Oil in ml Oil in ml Oil in ml Oil in ml Oil in ml Oil in ml Oil in ml
1,0 litres 50 40 33 29 25 22 20
1,5 litres 76 60 50 43 38 33 30
2,0 litres 100 80 67 57 50 44 40
2,5 litres 126 100 83 71 63 56 50
3,0 litres 150 120 100 86 75 67 60
3,5 litres 176 140 117 100 88 78 70
4,0 litres 200 160 133 114 100 89 80
4,5 litres 226 180 150 129 113 100 90
5,0 litres 250 200 167 143 125 111 100
5,5 litres 276 220 183 157 138 122 110
6,0 litres 300 240 200 171 150 133 120
6,5 litres 326 260 217 186 163 144 130
7,0 litres 350 280 233 200 175 156 140
7,5 litres 376 300 250 214 188 167 150
8,0 litres 400 320 267 229 200 178 160
8,5 litres 426 340 283 243 213 189 170
9,0 litres 450 360 300 257 225 200 180
9,5 litres 476 380 317 271 238 211 190
10,0 litres 500 400 333 286 250 222 200