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skin290

Rebuilding my 03 engine

4 posts in this topic

I posted this on my local BBS, thought I would get some of your positions/thoughts on it also.

Rebuild on my 03 YZ450F

Getting ready to rebuild my 450, last fall I went to practice and the oil drain plug in the frame fell out, ran it out of oil, and the only thing that seems to be bad is the intake cam spun in the head (screwed up the aluminum bearing surfaces). Well, I am sending that to Engine Dynamics in Cali, who specializes in weld build-up and repair of cam bearing surfaces for motorcycle engines, I got a used cam w/ 2 hours on it (almost brand new), and I am sending the head out today. I took all the valves out and need to check them for being bent and in spec, but they visually looked OK. Had one broken valve spring, that needs to be replaced as well (exhaust side, if I remember correctly). If anyone else has been in this situation, let me know what else you felt like needs to be done, I plan on cleaning out all the lines and the cases where the oil goes thru. I think a new oil pump was recommended, so let me know if anything else like that may need to be replaced.

Also, opinion on the piston, the bike has about 30 hours on it total, I haven't checked the ring and piston specs yet, but it is in OK condition (visual inspection) and I may or may not replace it depending on what the general consensus is on when to replace one.

I would like to know if anyone has suggestions for cleaning out the bottom end, lots of thin oil pumped thru, clean kerosene, or anything else I can do without splitting the cases?

Thanks in advance

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Piston will be shot if you ran her out of oil even for a few hundred feet. :thumbsup: You can probably save your crank and transmission but everything above the connecting rod should be replaced or inspected in detail. :thumbsup:

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I posted this on my local BBS, thought I would get some of your positions/thoughts on it also.

Rebuild on my 03 YZ450F

Getting ready to rebuild my 450, last fall I went to practice and the oil drain plug in the frame fell out, ran it out of oil, and the only thing that seems to be bad is the intake cam spun in the head (screwed up the aluminum bearing surfaces). Well, I am sending that to Engine Dynamics in Cali, who specializes in weld build-up and repair of cam bearing surfaces for motorcycle engines, I got a used cam w/ 2 hours on it (almost brand new), and I am sending the head out today. I took all the valves out and need to check them for being bent and in spec, but they visually looked OK. Had one broken valve spring, that needs to be replaced as well (exhaust side, if I remember correctly). If anyone else has been in this situation, let me know what else you felt like needs to be done, I plan on cleaning out all the lines and the cases where the oil goes thru. I think a new oil pump was recommended, so let me know if anything else like that may need to be replaced.

Also, opinion on the piston, the bike has about 30 hours on it total, I haven't checked the ring and piston specs yet, but it is in OK condition (visual inspection) and I may or may not replace it depending on what the general consensus is on when to replace one.

I would like to know if anyone has suggestions for cleaning out the bottom end, lots of thin oil pumped thru, clean kerosene, or anything else I can do without splitting the cases?

Thanks in advance

If you started to hear a high pitch sound that was also the bottom end. My friend did the exact same thing to his 2003. We put new cams, head, all new valve train, tensioner, piston & rings, cylinder, and clutch kit. Fired her up sounded fine, when put under load had a knock noise that we couldn't really hear on the stand. From that point on the noise just got louder. We should have completely split the cases and inspected everything. He said that the noise could really be heard good when short shifting into 4th gear, that really puts the engine under heavy load. I would take the extra time and split the cases inspect everything, don't half a$$ it. You will be much happier if you do. The extra parts won't be that much more if nothing is wrong (gaskets, o-rings, seals, some washers, yamabond).

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