Stage 2 PK-80 Top End Kit 80cc:
This Stage 2 Engine Kit provides turnkey performance for your PK-80, GT-5A, or GT-5SR engines that use a 40mm stroke crankshaft. This is not for the GT-5 Skyhawk. The cylinder body features additional widening of intake and exhaust ports. Transfer ports are smoothed to reduce turbulence. The newly redesigned intake plenum features a lengthened intake spigot which greatly enhances low engine speed performance. This kit also features a PHBG 21 mm racing carburetor which is connected to the intake manifold with a rubber hose coupler. Maximum power is achieved when the engine is connected to a good expansion chamber style exhaust system. The ample cooling capacity of CR Machine’s cylinder head will not only allow greatly increased output, but will also extend overall engine life by reducing the chances of detonation.
- Your choice of 5.3cc, 6.0cc, or 7.0cc chamber billet Stage 2 center fire cylinder head w/extra-tall nuts and flat washers *see note below
- 1 Stage 2 hand ported cylinder body
- 1 Billet special intake plenum with spigot mount
- 1 Rubber hose coupling with hose clamps
- 1 High quality Dellorto clone PHBG 21 racing carburetor prefitted with correct slide, needle and jets
- 2 extra main jets
- 1 High quality air filter
- 1 Modified PK-80 (Type-A) piston with rings
- 1 Wrist pin set
- 1 Aluminum head gasket
- 1 High quality base gasket
- 1 High quality exhaust port gasket
- 1 NGK B8HS spark plug
*For engines using race fuel, use either the 5.3cc or 6.0cc chambered head. For engines using normal pump fuel, use either the 6.0cc or 7.0cc chambered head. This is only a rough guide; optimal results are usually gained through your own experimentation. Other factors, like efficiency of exhaust system, rider weight, and road course layout will also affect which combustion chamber size is optimal. For example: Short courses that envolve short periods of full throttle can tolerate smaller combustion chamber volumes, whereas courses that envolve long periods of full throttle will require larger combustion chamber volumes in order to prevent detonation from occuring.
Squish clearance should be between .010 - .030"
- Before fitting the spark plug, gently rotate the engine to verify that the piston does not hit the cylinder head.
- Torque head nuts to 80 inch pounds; do not over tighten.