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Difference between 03+04 bottom ends? Trying to make good out of 2 engines!

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I have a 2004 WR450, it lost 5th gear and shortly after the chain snapped and wiped out the engine case.........:banghead: (I am never using a split link again!!!!)

Now, I have a spare 2003 complete bottom end sitting here (crank and conrod still in), but 3rd gear is broken (just slips, no drive) and I would like to use the best parts from both to make something usable.

The crank bearings etc are slightly better on my 04, so I would prefer to use that crank, if possible.

There seems to be a difference between the stators, I presume I need 2 different tools to remove them, 30mm and 33mm threads?

I have some concerns between the 2003 & 2004 compatibility due to the starter upgrade, the main one being:

Is it possible to fit my 04 crankshaft into the good 03 case, using my 04 stator etc or is the casing different?

Many thanks people :ride:

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I recently rebuilt an engine into brand-new casings, and the box stated that they were suitable for 2003 - 2006 engines, so I think it would fine.

Flywheels are different between the 03 and 04, and the size of the tapered area on the crank is also - use the 2004 crank and flywheel if possible.

The 2004 starter idler gear works on the 2003 model anyway, as it was the 'fix' for the problem with the earlier models

I would also be replacing the crank and gearbox bearings whilst it is pulled apart - cheap insurance if there has been metal floating around internally.

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