1980 yz 125 mosquito killer HELP - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 05-12-2003, 12:00 AM
**DONOTDELETE**
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1980 yz 125 mosquito killer HELP

my son and i just bought a bike for fifty bucks. cleaned carb and tank replaced spark plug started right up blew smoke out from under the head. replaced head gasket started up blew massive clouds of smoke and oil out the pipe. my son says bad seal between the crankshaft and the rest of the motor points to gas mixed into the oil in the crankcase. i say there is no seal between the crank and the rest of the lower end, must be wasted rings. any help?
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post #2 of (permalink) Old 05-17-2003, 12:57 PM
sunnyboy
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Re: 1980 yz 125 mosquito killer HELP

SOUNDS LIKE YOU AND YOUR SON ARE STARTING A FUN AND EDUCATIONAL PROJECT.YOUR SON IS CORRECT.THE BIKE IS A 2-STROKE MOTOR AND HAS NO RESIVOR OF OIL IN THE CRANK CASE LIKE YOUR CAR,OR IS NOT SUPOSED TO.ALL OF THE OIL FOR THE MOTOR IS CARRIED IN THE GAS, THIS IS WHY YOU MIX OIL WITH THE GAS IN YOUR TANK.THE OIL YOU DRAIN FROM THE BOTTOM OFF THE MOTOR IS NOT CRANK-CASE OIL IT IS TRANSMISSION OIL AND SHOULD NOT BE CONTAMINATED WITH FUEL.THE RIGHT CRANK SEAL IS LEAKING.BOTH SEALS SHOULD BE REPLACED,RIGHT AND LEFT.YOU NEED TO GET A SHOP MANUAL FOR THE BIKE IF POSSIBLE,ANY YAMAHA TWO STROKE MANUAL WILL BE OF GREAT HELP.ALL OF THE SEALS SHOULD BE REPLACED, THE BEARINGS SHOULD ALL BE INSPECTED ETC.IF YOU DO YOUR JOB RITE, YOU WILL END UP WITH A MOTOR THAT WILL LAST A LONG TIME, AND GIVE YOU LOTS OF FUN.---------SEEYA ON THE MOUNTAIN--SUNNYBOY
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