Mechanical problems discussed for Dirt Bikes and Dual Sport Bikes
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Joined: Thu Jun 07, 2012 3:50 pm
Location: Eugene, OR


Post by Sandblaster » Tue Sep 25, 2012 4:36 am

A customer brought in a 2004 YZ450F Yamaha that has severe overheating issues.
His pipe got so hot he melted his air box.
After idling for just a few minutes his header was cherry red it's entire length :shock:
So, what is the problem?
Our affiliate at Dirt Bros. Racing took the bike and checked all the obvious things.
Here is what he found.
The valves were out of adjustment.
The carburetor insulator boot was loose and potentially leaking air.
The air box filter had holes in it.
The air box had a bunch of debris that had got past the filter.
The oil screen was clogged.
The fuel/air mixture screw was leaking air.
The hot start was leaking air.
The pilot jet was too small.
The oil was a heavier viscosity then recommended.
All of those things could contribute to the engine running too hot.
In the end, the oil filter was installed backward :(
This was made possible because a aftermarket oil cover was used that did not have the bar sticking out that would prevent this from happening.
Once the filter was replaced and installed correctly the heating issue disappeared.
There was also some fine aluminum particles in the oil when it was drained.
Unfortunately this doesn't bode well for this engine.
So, please learn from this guys mistake, INSTALL YOUR OIL FILTER IN THE CORRECT DIRECTION!!!!
If bikes are for kids I'll never grow up.

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