Stage 2 Cylinder Head w/Compression Release 66/80cc:
This is our Stage 2 cylinder head for the 66/80cc GT-5 or PK-80 motorized bicycle engine with 8mm studs. This newly designed angle fire cylinder head is designed to be used with stock single spark ignition and comes pre-fitted with a nice NOS compression release mechanism. Available in 6.0cc or 7.0cc combustion chamber volumes. Takes the miniature 10mm spark plug: NGK C7HSA, included.
NEW!!! Pick the thread pitch of the head nuts!! Choose either fine pitch (1.00) or coarse pitch (1.25)
Coarse thread cylinder head nut torque spec: 60 inch pounds
Fine thread cylinder head nut torque spec: 48 inch pounds
When setting up or making adjustments to the compression release valve, make sure it doesn't open too far, as the piston could hit the valve poppet.
Please be aware that in order gain the maximum benefit from this cylinder head, you will need to bring the outer edge of the piston to (or close to) the top of the cylinder. A close "squish" clearance has better combustion efficiency. If you have a GT-5 engine, using a shortened cylinder body will produce optimal results. Check out our cylinder bodies and complete top end kits for the GT-5 engine.
The increased cooling capacity of this head will not only extend the life of your piston and cylinder, but it will also allow increased output.
WARNING: If you plan to use this head with a compression release, your bike must not be equipped with a shift kit or other type of spring loaded tensioning device!
Add a top gasket for an additional $4.