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:
Please also check out these two sites as they provide a wealth of information and are full of fellow enthusiasts willing to share their knowledge and experiences:
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:
1 – expander ring – (wavy one) – lower groove
2 – lower oil ring – below above ring in lower groove
3 – upper oil ring – above expander ring in lower groove
4 – install the black one in the center groove
5 – Install the silver one in the top groove (markings on ring should face up)
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:
– Make sure the 20mm carburetor kits are put on like this: Cylinder head > gasket > plastic heat stop > gasket > intake > carb
– Make sure your ground wire is not loose and connected to bare (not painted) metal as this may cause issues similar to carb issues. 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 kits with the Mikuni VM26 carb, here is a link to the Mikuni manual: