i recorded this earlier and posted it on you tube to get some opinions on what might be wrong with my 2002 yamaha warrior.its makeing a weird knocking sound around the engine section and when i started it up it there was white smoke coming out the muffler for about 5minutes untill it cleared up.
check it out heres my youtube link

YouTube - 2002 yamaha warrior 350 knocking sound

 

once again warriors arent a quiet motor and its an old 4 stroke, the valve seals are gonna leak a little bit of oil on start up

 

iv built countless trail race atvs, as these are my speicalty, and ill tell u now the warrior/raptor 350 are one of if not the best platform to start with.... why...simple, small wheel base, good sized engine, masssive aftermarket and used parts support, and probly the most cost effective bike in the world to build. look at it like this, the warrior was around for almost 15 years UNCHANGED except for mild electrical and suspention parts. which gives it a HUGE advantage for building a used machine from the ground up. granted its not the most technalogicly advanced machine, but with a few basic mods ( oil cooler and greasable swing arm/carrier baering) this bike WILLLLLL NOT DIE. over heating, whats that, alll day rev limiter bounces, ehhh, lack of oil changes, who cares, iv personaly seen these bikes run with MASSIVE crank and rod bearings clearances and serious piston skirt damage and other than some noise and smoke run alll day. the biggest thing that killls these bike is ppl who put aftermarket cdi boxes on them with higher rev limiters. which will killl almost any motor. there is a lack of factory performance from the engine but with mild work and minamal money these bike WILLL power stronge and although it wont be a 400ex, ( WHICH PLS REALIZE THE 400EX HAS 4 VALVES, A BETTER CARB, AND OTHER SERIOUS DESIGN GAINS) it will cost u way less to build if done rite, plus ALLLL warriors have reverse unlike 400s plus the 6 speed tranny provides exceptional trail rideing capability and sproket choses due to the gearing. and again u can buy parts bike alll day for 500 or less unlike any other quad in its class. the suspention it fine unless ur over 160 lbs which is max weight for this bike which many ppl forget, most new bikes are designed for fat *** 200 lbs "racers". - donny

 

Its hard to tell in the video, but it almost sounds normal - maybe an exhaust leak? I had problems with my Warriors splitting the headpipe right up by the head but you couldnt see it until the pipe was clean.

 

I also thought it sounded like a leak especially from the left side.