Honda

TBparts.com highly recommends a professional technician or your local Honda dealer install the performance parts for you. If planning on installing the kits yourself, there are helpful “must have” manuals, such as Clymer’s (visit www.clymer.com 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.

Please also check out these two sites for all kinds of technical, historical, and other model info on your bike:

www.planetminis.com

www.lilhonda.com

These sites 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.

Honda 50/70 Engine Tear Down Instructions

Honda 50/70 Bore Kit Installation Instructions

Honda 50/70 High Volume Oil Pump Installation Instructions

Honda 50/70 Manual Clutch Installation Instructions

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

http://www.mikuni.com/pdf/vmmanual.pdf