[Kyle450x]

Hey all. I have a 2005 CRF450X that i've had since 2007, and have put a good amount of miles and hours on. About 3 years ago my 5th gear went out, so I had it professionally fixed. This last November while pre-running down in baja I lost 4th gear:(. I had to ride it to the nearest town (10 or so miles) where I put her on the chase truck. I haven't touched her other than draining out the Pemex gas.

I always run the full quart of transmission oil, and never slam the shifter (knowingly).

I am finishing up another bike project I had going on, which means I need to pull apart the 450X that has been staring at me every time I pass her in the garage.

Should I upgrade the parts to a certain year's parts? As far as I know, the shop I had do the repair last time said they were the updated parts.

Perhaps have the gears and shift forks shot-peened for extra strengh and oil holding properties? I really don't want to have to rebuild the tranny again...

I am very curious to hear everyone's advice on this matter.

Thanks!

[JimDirt]

It seems strange that you have had so many failures while using a full Qt , which was the "fix" for grenading tranny's , its definitely something either bad that was not replaced (main shaft or something)on the original rebuild , or possibly a assembly issue where the shimming was done incorrectly , and is causing pressure/load on one of the parts

Has there been any regularity to what part fails or coinciding parts that along with the main part failure , is consistent ???

The only thing i am aware of is a polishing process , but i do not know if that would prevent any failure you are experiencing , since the cause is not known at this time , i would ask Ken , and see if he has any answers

This is the polishing process i am referring to
http://www.crfsonly.com/catalog/product ... ts_id/4446

Hope that helps some , sorry , i don't have any affirmed answers

[crfsonly]

Hey Kyle...sorry to hear about this second trans issue. It's certainly not the norm. While I can't speak directly to either failure I can tell you installing a trans demands meticulous installation of each part. Not only do the gears have a specific orientation but so do the thrust and spline washers and snap rings. Snap rings also have to be position on the shaft correctly. Some will reuse snap rings which is not recommended as a worn snap ring can spin in the groove. Besides these details, I'd recommend replacing all of the trans parts for your project unless you are able without a doubt to positively identify the failed part(s) and verify all of the other parts are in spec. Having a bike fail in Baja, whether pleasure riding or racing, is expensive and disappointing. At this point it might make sense to ensure this does not happen again. Worn shift forks, shift drum, shafts, bearings all play a part in proper function. Alignment and clearances with each of these parts is critical. ISF treatment we offer is great for reduced friction/heat and smoother shifting but it won't fix trans parts not in spec or not in the correct orientation. Please know I'm not suggesting that was the case with your transmission just mentioning these details for all reading and considering splitting the cases for any reason.

Ken

[Kyle450x]

Hey Ken,
Thanks for the reply. I am definitely considering having it done professionally, but am still trying to find some way of "upgrading" it this time. Although I had the ISF done previously, I couldn't feel much of a difference while riding.

Through my engineering courses, professors have often talked about shot-peening parts for post-production strength benefits.

Food for thought from a shot-peening site: "As the shot strikes the gear it peens the surface, leaving very small indentations or dimples. These overlapping dimples develop an even layer of metal in residual compressive stress. This compressive stress is a good thing for it is well known fact that cracks will not initiate or propagate in a compressively stressed zone, such as the root radius of the gear teeth, where nearly all gear teeth failures start. Rule of thumb: shot peened gears generally will exhibit strength of a gear that is 25% larger in cross section."

I think I will at least dissect the engine myself (very confident with that procedure), and possibly split the cases myself to inspect and study the broken parts. Like you say, I wouldn't have a new shift fork, or gear etc to compare it against, so the safe bet would to be to replace everything no doubt.

I'll post updates once I tear it apart or have it torn apart

[crfsonly]

You're welcome. Definitely keep us updated. If we can help you with any of the parts you need let us know. You can find all the trans parts on our OEM parts website, www.yeltrik.com.

Ken