CRF250X project

Picked up this low hour 2006 CRF250X April 27th, it had a LOT of bad engine noise, like a bucket of bolts being shook hard. It's a gamble, fix or part out, we will find out as we dive into the motor. This is also a great learning experience for my son blake, he's really into riding, and riding is very expensive if you cannot fix your own machine.


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Disasembling the 250x

Getting deeper into disassembly, everything must be disconnected from the engine, to make life easier we unhooked the rear shock from the top mount, and the rear subframe, Blake held the subframe up for me, while I rotated the engine, turning it clockwise and tilting it rotated out of the frame, it did involve some swearing


Take your time doing this, if you dont follow the book/manual you'll wonder why something wont come out or move. Watch out for the clip behind the rear brake pedal, you need the pedal off to remove the swingarm bolt. Your gonna be unhooking the carb, and unhooking wires, it's labor intensive.












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Pulling Engine out

Engine out, took about 1 1/2 hours to get to this point, starting disassembly from top down, head looks good, piston looks almost new still, cylinder has no damage. All the internal carnage was on the transmission side oil, these engines keep the crank/cylinder oil separate from the transmission oil



There was quite a bit of oil up top at the cam, the oil pump was still semi working



Crosshatching still looks good!

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Going in deeper

Going in deeper now, I already know at this point that the damage is on the clutch side, there's no metal debris in the crankcase oil side.



I'm greeted by loose parts, a nut, washer, insert and half a bearing!



Here's the culprit, balance shaft, either the nut came off, or the bearing went first and then the nut came off, either way loose parts, and several gears damaged. You can see case damage where the balance shaft gear dug into the case, thankfully it was not too deep, plenty of material left. Unfortuantly this spit the aluminum back towards the transmission gears, where it entered the center case. This means the case has to be split to inspect all the gears & bearings, and to clean out any debris that made it in there.


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The part that caused the problem

Here's the problem part, this is a counter balance shaft with gears, thankfully ebay is a good source for replacement parts, both gears need replacement




Piston wear, pretty normal for low hours




Crank end wear, within spec, still round



original coating still not worn off all the way


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cleaning and prep for assembly

Cleaning parts by hand sucks, so we picked up a small 3.5 gallon parts washer today at northern tool and equipment, 49 $ and 5 $ in water based solvent.



Clean parts, waiting on part orders to come in now



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The right tool for the job

The right tool for the job makes all the difference, those case bearings are really in there, using a proper slide puller makes all the difference, and it's really not that expensive, 49 $







This bearing was just the outer race, inner & balls were gone, to fit the extractor I had to use a hose clamp to clamp down the extractor to get it to fit in, the next smaller size was not big enough, and the one I used was too big to fit in without clamping it down



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