KX Guru Racing

My RMX250 Shift Drum looks damaged. How can I tell if it is good?
Looking to the Service manual for information is almost always your best option.
In this case I don't have the service manual specific to the RMX250 but I do have one for the RM250.
As it turns out, the manual I have also has some specs for the RMX250 and we got lucky as it specifically lists the RMX250 drum specs.
Take a look at the pic below.

As you can tell, the single most important thing on the drum is the groove width that your shift forks slip into.
Here is a pic of the specs.
It lists the drum groove width as 4.8mm - 4.9mm or .189" - .193"
Of course you want to make sure that the other things mentioned to look for are good as well such as the pin condition, thread condition, drum bearings, ect.

I have a potential customer that has asked a very good question.
It seems that his shift drum as well as one that I am selling appear to have the same problem.
Here is a pic showing the potential problem.
I realize that these look really bad.
However, take a close look...
Are those machined edges?
No, they are cast. So those edges that appear to be damaged are nothing more then casting flaws.
They do not have anything to do with any of the machined surfaces that capture the bearings or hold the shift forks in place.

How can I be so confident?
Well, here's a pic of 5 different shift drums, all from RMX250's from 1990-1998 and they all have the exact same appearance.

Confused?
Take a look at this pic.
It shows the edges and surfaces to be concerned about.
This pic shows the area that I would take my Dremel tool too and clean it up to remove casting flash or rough surfaces.
Not because it is mandatory, but because I'm fussy and I don't want some little chunk falling into my trans area and dinking up a gear
Any questions?
Feel free to ask.