Changing Oil & Gearing23 January 2019
This evening I changed the oil on the KTM. Unlike some other KTM models (cough cough RFS cough cough), the RF4 motor in the 505 XC-F is pretty easy to service. I used 1.25L of Motorex 10W-50 synthetic oil and a K&N filter, and it was all finished in about 25 minutes. No fuss, no mess!
I also wanted to change the countershaft (front) sprocket from a 13-tooth sprocket to a 14-tooth sprocket. This will give me a little more speed for the same RPMs. I previously was using the bike for more trail riding. I have a 46-tooth sprocket on the rear wheel and I'll leave that as it is.
Changing the countershaft sprocket on a KTM dirt bike is pretty easy. I loosened the rear axle and slid it forward, giving me plenty of slack in the chain. I also loosened the countershaft sprocket guard and moved it out of the way. After removing the countershaft sprocket bolt and dome washer, it was easy to slip the 13T sprocket off.
At this point I noticed there was a bit more oil there than there should be—the countershaft seal was leaking a little. This is a normal wear item, so it's fairly easy to replace. Unfortunately, I had to order the parts (about $25 in total), so I finished the sprocket swap without addressing the leak. The parts should be here at the end of the week and then I can replace the seal.
On the plus side, the chain was already long enough to handle an additional tooth on the countershaft sprocket without having to add a another link.