03 YZ450F Crank Problems

[03yz450f-43]

I have been advised that the crank in the 03 YZ450F is a potential failure mode. I was told that to make the bike lighter, the crank was not as substantial as it should be and that the cranks on the 2004 were beefed up. Any feedback on this?

Thanks,

[grayracer513]

The only difference in the two cranks is the connecting rod. But whatever the improvement was, the "danger" of an '03 blowing apart is somewhat exaggerated. I personally have never heard of a con rod failure in that engine. Maybe in a supermoto or 1/2 mile engine? Still, if you were ever rebuilding, it would make sense to use the upgraded assembly.

[03yz450f-43]

Thanks,

The motor is apart so I think I'll go ahead with the upgrade.

[boyonblue52]

My friend threw his rod bearing in his o3 yz450f one day while riding. Kept up on all his check ups and one day she just went. Maybe this helps you with an idea?!?!?!

[FFRacing79]

The only difference in the two cranks is the connecting rod. But whatever the improvement was, the "danger" of an '03 blowing apart is somewhat exaggerated. I personally have never heard of a con rod failure in that engine. Maybe in a supermoto or 1/2 mile engine? Still, if you were ever rebuilding, it would make sense to use the upgraded assembly.

There were severaL lower end failures on the '03s that I am aware of. But there is nothing harder on these motors than 1/2 mile and Mile racing. On the Miles, they are actually wide open for the entire race! Tdub

[Ga426owner]

What are the performance differences between the 03 and 04 crank? That motor was a little softer than the 03....

[grayracer513]

The "softer" performance you speak of is, to the best of my knowledge, entirely due to a different ignition map. Almost everything else is nearly identical.

[FFRacing79]

The intake tract is also different. The '03 head is no longer available. Tdub

[grayracer513]

The intake tract is also different. The '03 head is no longer available. Tdub

Was that the smaller port diameters and the reconfiguration of the diversion into 3 individual ports? The piston is also a different part, which I had thought was to match the reshaped chamber, but I don't think either of those things softened the character of the engine any.

Thoughts on that Tryce? Which head do you think makes more power?

[rasta]

My friend threw his rod bearing in his o3 yz450f one day while riding. Kept up on all his check ups and one day she just went. Maybe this helps you with an idea?!?!?!

same here, my rod bearing went out about 6 months after owning bike. i worked at a shop at the time so it was well maintained but anyways cost me $1,600.00 for dealer rebuild. it did blow up the following ride in the first 10-15 minutes but thats another story.

[FFRacing79]

Was that the smaller port diameters and the reconfiguration of the diversion into 3 individual ports? The piston is also a different part, which I had thought was to match the reshaped chamber, but I don't think either of those things softened the character of the engine any.

Thoughts on that Tryce? Which head do you think makes more power?

The '03 head was by far the easiest head to get power out of. Intake roof got lower every year( the YZF got "mellower" each consecutive year), depending on which tuner you talk to, made it more difficult to work with.