misc tech Information

chinese engine info

chinese and trail bike kits

Besides performance kits the small Honda’s and Kawasaki KLX110s, we also sell some kits for the Chinese pitbikes and trail bikes.  Most of the Chinese engines are based on or are copies of the small Honda OHC single type engines.  There are a few, namely the YX150/160 and Zongchen 155, that use a Honda type bottom end and a Kawasaki KLX110 type top end.  With a picture of the engine, we can tell you which type your engine is based on (Honda or Honda/KLX) but that’s about all we will be able to tell you.  There are and have been so many variations and brands of Chinese engines made over the years and unlike Honda engines, the serial numbers are meaningless.  So, we can’t provide specs of your engine like the bore and stroke etc.  If you are unfamiliar with what you have, you basically have two options.  One is to contact the dealer who sold you the engine and/or two, disassemble and determine the specifications yourself.   Our recommendation is to not buy a used Chinese engine unless you are very familiar with them.   It’s worth it to pay a bit more for new Chinese engine from a reputable vendor with a long history of selling them.

Regardless of which type of Chinese engine you have, TBparts.com highly recommends a professional technician or local shop install the performance parts for you.   However, if you decide to install a kit yourself, virtually all the performance parts install exactly like the stock OEM parts.  So, if you can get shop or service manual from the company you purchased the bike from it would be extremely helpful.

If you can’t get a service manual for your particular Honda type Chinese engine, then we would recommend getting the Clymer Z50 XR50 Manual (visit www.clymer.com or see our online store in the Z50 XR50 Engine section). While the specifications of your engine may be different, all the principles of installing a new top end and/or other parts will be the same.  Additionally, this manual will instruct the novice mechanic on how to rebuild an engine and maintain it properly.

If you can’t get a service manual for your Chinese engine that has a Honda type bottom end and Kawasaki type top end, then we would recommend getting the above Clymer Z50 XR50 Manual and also a Kawasaki KLX110 service manual. You can purchase the KLX110 Service Manual at any Kawasaki dealer.  There is also a free download at this site:

web resources

Please check out this site for all kinds of technical, historical, and other model info on your bike: www.planetminis.com  It covers almost all pitbikes as well as vintage Honda mini models. Simply use the search function once on the site to find the info you are looking for.

Also check out facebook.com and join several of the groups covering your model mini. 

Planetminis.com and Facebook groups provide a wealth of information and are full of fellow enthusiasts willing to share their knowledge and experiences.

Online Manuals

We have provided some information below that will be helpful. However, please don’t consider it a substitute for having a professional install your kit or the manuals we recommend above.  Additionally, these instructions are for Honda’s and your Chinese engine may have different specifications.

Note:  For all kits that include stroker cranks, they are installed exactly like a stock crank so you will need either a Clymer or Honda shop manual for instructions. The following are common installation errors when installing bore kits and the clutch kits: – Installing the cam incorrectly which results in loud knocking. Make sure when you line up the 0 on the cam sprocket with the mark on the head, the cam lobes are facing down towards the piston. – Clutch nut not torqued on (after installing oil pump) which will result in knocking, spline damage etc. Please do not try to tighten the clutch nut with a hammer and screwdriver – use a clutch nut socket. – Putting the piston rings on incorrectly – All TBparts.com rings should be installed this way and in this order:

Make sure the end gaps of the piston ring are not aligned with one another -evenly space apart

Carburetor Kit Info

Its impossible to really provide jetting help via phone or email as every bike is different and we just don’t have the time to compile all the scenarios (location, temp, other performance parts etc.) and especially, the exhaust info – there so many different types available.  We have listed below some things that may help if your bike is not running properly:

This problem happens quite often. – Try a plug chop – run it at high rpms and then kill it and check the color of the plug. Based on your plug reading, you may need to move the needle clip or go with a different main jet depending on if it is running rich or lean. When running properly, it should have a nice light brown plug color. If not familiar with how to read a spark plug or make basic carburetor adjustments such as moving the clip or changing the main jet, we highly suggest picking up a Clymers Manual as it covers these routine procedures.

For bogging, try adjusting the airscrew – back the air screw out 1-3/4 turns as a baseline to begin. Make 1/4 turn increments in with the air screw to get it right – usually ½ to ¾ is where you will end up on the 20mm carburetor. – Make sure you did not over lube the air filter. – Use fresh clean high-octane gas (race gas not needed). – Check for air leaks. – Check your petcock and fuel line to make sure you have good fuel flow. – If you experience backfiring, make sure you reinstalled exhaust gasket and that the exhaust is tightened down and there are no air leaks. – Double check valve adjustment after you have ridden it with a new bore kit installed.

For the Mikuni VM26 carb, here is a link to the Mikuni manual:

Valve Lash Settings For All TBparts performance

Cylinder Heads and Camshafts

0.003” for both the intake and exhaust valves. Some valve tick is normal due to this gap that is needed for clearance when the engine heats up to normal operating temperature. 

Camshafts and Timing an Engine

In all applications regarding the use of TBparts – Install the camshaft with the lobes down or toward the piston. This first step combined with aligning the camshaft timing marks and crankshaft timing marks will ensure your engine is timed properly.

Piston Ring End Gap

Four thousandths of an inch (0.004”), per inch of bore is the standard measurement we use for all TBparts piston ring kits. You can use the chart below to make sure your new TBparts piston ring kit falls in the safe clearance range. Running too tight of a clearance can cause seizure of the ring in the bore causing catastrophic piston failure. Running too loose of a clearance and you will lose compression there for horsepower and burn excess engine oil.

Ring Gap Chart



Ring Gap   (0.004″ per inch)






0.0055″ – 0.0065″




0.007″ – 0.008″




0.0075″ – 0.0085″




0.007″ – 0.009″




0.007″ – 0.009″




0.007″ – 0.009″




0.008″ – 0.01″




0.008″ – 0.0115″




0.009″ – 0.012″




0.009″ – 0.012″




0.009″ – 0.012″




0.009″ – 0.012″

Spark Plugs & Heat Ranges

Spark plugs are available in various heat ranges, hotter or colder than the factory installed plug. In general, use a plug one range cooler in high performance or high-speed applications. This combats hotter running temps to avoid overheating. When you have a stock engine running constant at low speeds or in cold weather applications use a plug one range hotter for smooth engine operation.

Note – Spark plug ranges with a higher number are cooler. A lower number will be a hotter plug. For example, the next range cooler for a commonly used CR6HSA or CPR6EA-9 is CR7HSA and CPR7EA-9 which would be used in a performance application like adding a big bore kit.

Import/Chinese Engine Spark Plug Info

Model OEM Plug (NGK) Plug Gap
Daytona 190 4 valve ER9EH or ER9EHIX 0.6 – 0.7mm
Lifan 125cc 54x54mm bore/stroke CR6HSA 0.6 – 0.7mm
Lifan 50,70,110cc CR6HSA 0.6 – 0.7mm
YX125 & YX140 CR6HSA 0.6 – 0.7mm

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