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tzracer46

Blown up 450 engine.

16 posts in this topic

Hey guys. I just picked up an 03 450 with a blown up engine. I got it for a good price so I don't feel too terrible about the damage, but it's got alot of it. The small end of the rod broke and basicly turned the engine into scrap. It took out the head, cylinder, cases and balancer shaft. Anyone seen this happen before? Any idea what could have caused it? The wrist pin is still intact and in the piston and really doesn't look too bad considering that the rod is now sticking through the front of the case.

Thanks,

Mark

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The most likely things that I can think of for a broken rod are seized piston (check the cylinder and piston for seizure marks), or overrev induced by either a bad rev limiter or more likely by someone down shifting when they should not have.

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the same thing happened to the local shop mechanic's 450. he figured out that the rod wasnt forged all the way and it just snapped after a lil bit of riding. it grenaded his pretty bad but hes got it goin again and runs like a beast!

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My brothers 03 wr450 did that on Sunday. Shifting into 4th doing about 90kmh the rear locked and it was all over. The only thing we found was a radiator hose was half off. Probably caused by an earlier stack. Put it down to overheating. Stuffed the bore, an intake valve, piston is nearly sideways in the bore, conrod broke through the cases below the starter motor. Made a huge mess.

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I just did a little checking on Yamaha 's web site. The part number for the rod is not the same on the 04 as it is on the 03. the 03 is a 5TA-11651, and the 04 is a 5XD-11651. All the other numbers are the same. Does this mean Yamaha knows there was a problem with the 03 rod and changed the part number to fix the problem? Is there something they aren't telling us? Anyone see this problem on an 04 yet or is it just limited to the 03's? Maybe someone who works for a dealer can check the 03 part number and see if it updates to the 04 part. I don't want to put another 03 rod in and have the same thing happen to it.

Mark

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i hope its not a problem with the 04-ive been riding the wheels off mine since the end of 03 and have had no problems. :thumbsup:

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I read here almost daily and I have seen relatively very few people complain about broken rods. I don't think it is a major problem. Take a look at the parts and see if you can determine exactly why it broke. I would say that bad design should be eliminated from the list simply because there are so few broken rods reported.

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if you want to sell it let me know!

or if you guy have a friendwho want to sell the broken 450 let me know!

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So do the Race Tech Gold Valves help out the fork's performance any? Can someone describe the difference it makes on the forks?

Thanks,

Chas

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Take a real good magnifying glass and light and examine the broken rod ends at the fracture point. If it is not beat up too bad you might be able to see what are called "beach marks" this is evidence that the rod started to fracture first. Beach marks look like the lines in the sand left by varying water levels. Typically the beach marks will go across and stop at the point at which the rod finally fractured the rest of the way through.

I doubt this will get you anywhere with Yamaha on a warranty clain but it might be good info for any 03 owners?

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So I bought that used engine off of ebay. I'm going to tear it down and put a new rod and piston in it just because I don't know the history of the engine and don't want to end up with another engine with the rod thruogh the cases. Anyone have any opinions on stock rods and pistons vs. aftermarket? Come on lets hear it I'm counting on you guys not to lead me astray.

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I respectfully disagree...I would love to have the engine for either 1.to build it out with a big bore kit and better cams & internals or

2.I would call Doug at DRD and ask him about one of his special porting jobs with all the DRD motor mods as tested in this months MXA. :thumbsup:

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