Some bad news

January 5, 2010

About a week ago I went to change my YFZ 450’s oil for the first time since I bought it used. First issue was the previous owner had stripped out the oil tank drain bolt, and after removing the tank (to re-tap the drain hole) I discovered a lot of steel metal flakes in the crud on the bottom of the tank. Great, metal flakes in my oil!

After taking some advice from people on the Yamaha quad forums and a shop I decided metal shavings were a bad sign and it was time to brake the engine/transmission open to see what the problem is before there was a catastrophic failure. the shop guy said stel shavings could be a number of things, including the transmission. The previous owner was an idiot, so I’m wondering what all I’m going to find in there.

Assuming there isn’t horrible permanent damage I’m planning on rebuilding the engine for more reliability and a bit more power. Right now the idea is:

-Yamaha WR450 dirt bike OEM crank and rod, and piston. Fits in the YFZ motor and has a smaller wrist pin that allows the piston to have more metal around it (18mm vs the 20mm on the yfz). Is also lighter.

-CP 12.5:1 piston, or Venom 12.25:1 piston – very nice 3-ringed pistons, add a bit of compression, but still allows for pump gas. Possibly just go with OEM piston if I cannot find the right compression ratios in the aftermarket pistons.

-J&T oil upgrade – on the ’04-’06 models Yamaha used a ‘splash design’ to lubricate the wrist pin and piston rod bearing which obviously has cause many people problems (possibly me). The upgrade updates the engines to the ’07+ models with a better pump and oil squirters.

Metal and other fragments on the oil sump pickup

magnetic metal bits found in the oil tank

My work area

Getting stripped

Engine out of the quad

Is something missing?


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