Honda Tech

Resources and tech articles

tbparts recommends only using

Professional Tech's highly recommends a professional technician or your local Honda dealer install the performance parts for you. If you are planning on installing the kits yourself, there are helpful “must have” manuals, such as Clymer’s (visit or see our online store), that will instruct the novice mechanic on how to rebuild an engine and maintain it properly. Honda also has shop manuals for the more advanced mechanics. In most cases, both can be ordered through any local Honda dealer (we also stock the Z50/CT70, XR50, and XR80/100 Clymer manuals and the Honda XR50 shop manual). Both manuals also provide many important specifications. Virtually all the performance parts install exactly like the stock OEM parts and that’s why these manuals are extremely useful.  

web resources

Please check out this site for all kinds of technical, historical, and other model info on your bike:  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 and join several of the groups covering your model mini. 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 manual we recommend above.

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 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

It’s impossible to provide accurate 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.

Honda Spark Plug Info

Model OEM Plug (NGK) Plug Gap
Z50A K0-K6 and or 1968-1978 C6HSA 0.6 – 0.7mm
Z50R 1979-1981 C6HSA 0.6 – 0.7mm
Z50R 1982-1999 CR6HSA 0.6 – 0.7mm
XR50 & CRF50 2000+ CR6HSA 0.6 – 0.7mm
CT70 & CT70H K0-K6 or 1969-1982 & 91-94 C7HSA 0.6 – 0.7mm
TRX90 1993+ CR7HSA 0.6 – 0.7mm
ATC, TRX70, SL70, XL70 C6HSA 0.6 – 0.7mm
CRF110 CPR6EA-9S 0.6 – 0.7mm
Grom 125/MASX125 2014-2020 CPR6EA-9 0.6 – 0.7mm
Grom 125/MASX125 2022+ CPR7EA-9S 0.6 – 0.7mm
Honda Monkey 2018-2021 CPR6EA-9 0.6 – 0.7mm
Honda Monkey 2022+ CPR7EA-9S 0.6 – 0.7mm
CRF125 CPR6EA-9 0.6 – 0.7mm
XR100 & CRF100 CR7HSA 0.6 – 0.7mm
CRF150F 2003-2005 DPR8EA-9 0.6 – 0.7mm
CRF150F 2006-2017 CPR8EA-9 0.6 – 0.7mm

Get exclusive offers!