Quote Originally Posted by MJH View Post
Honda still uses the RFVC in the XR line...

that engine was in the XR400 from 1996 to 2004
Ive got a dual carbed '85 250R, '87 600R and have been looking for a 350R


the dual carbs RULE when they are right but all of them were heat sensitive, they would crack the heads between the exhaust port and spark plug holes, still ran but smoked blue.

never run them lean, never block the tank vent tube, never let them get caked with mud. run a cooler spark plug and get a temprature guage/ dipstick. spare heads are hard to find these days.

is the 3rd xr250 i've built and the one iv'e got in the garage stripped down is now calling me, had the frame shot blast ready for coating, pulled the engine apart ready to put a nice 277 in there and the bloody head is cracked,

Nov 2011 ... I have a chance to pick up a 4 valve rvfc xr 200 engine cheap. The head is
cracked

in my life as a tig welder i have welded up dozens of these heads

the design is flawed