I have a new Kazuma Falcon 250. I've got it tuned up pretty good. Only a couple of problems. The engine vent tube has a lot of air coming out of it. Sounds like a small muffler. In my opinion it is most likely blowby from the rings. The next problem is at 3/4 to full throttle the engine spitters and sputters, sounds like detonation or misfire. I have a new NGK plug installed and tried a second to eliminate this as the problem. The next problem is with the temp warning light. When I have the headlights on and give the engine gas the red light comes on. I checked the temps with an infared pyrometer and they are 190F coming out of the engine/into the radiator and 140F coming out of the radiator and into the engine. The fan never comes on either. I drained and bled the cooling system several times refilling it with 50/50 coolant water mix, fresh each time since it came out a little hazy. When the horn worked the red temp light would come on while the button was pressed as well. I checked all the grounds I could find and unplugged/replugged all the electrical connectors to try to get rid of some of these problems as well. If anyone has any input or suggestions on these issues I'd appreciate any feedback.

Thanks

i8amm
Yamaha Warrior 350
Yamaha YT 175
Yamaha YZ 80
Yamaha GT 80
Honda QA 50
Honda 200sx
Yamaha YZ 400
Falcon 250

 

Your temps seems ok. the fan on my suzuki rarely comes on, just as long as your water is flowing you should be good. Your sputter problem could be incorrect jetting . that vent tube you describe sounds like your biggest problem , i'd check the compression I've never even noticed anything like that comming from any of my bikes. I've got a couple redcat quads vx and dpx 200 they have less than 5 hours on them and I see problems already ,sorry I ever bought - them lesson learned