Stage 4 Hop Up Kit for GX390The Stage 4 kit starts with a package similar to that of the
Stage 3, but adds a ported and milled head with stainless valves, a stud kit, and heavy duty valve train components. Allows up to 35+ HP out of a GX390.
*Note: This kit only fits 389cc (88mm) engines. Kit is intended for experienced engine builders. Some clearancing, fitment, or other engine building "tricks" may be needed. Picture is for reference only. See above description for actual content. Filter should be sprayed with K&N type oil, especially in dirt applications. Oil not included -
click here. Billet aluminum flywheel required.
UT2 series Hondas (2012 & up) or later have a built-in rev limiter in the coil and will require a new coil to exceed 4000rpm. The UT2 coils (4 wire) can only be used with stock flywheels. If using a billet flywheel, you must run a UT1 style coil (single wire).
13/15 Chinese engines (414, 420, 460) usually have UT1 style coils already. However, some Lifans and 420s have a digital ignition and will need a Honda UT1 coil to run the billet flywheel. 
