You ask we answer. Here's the latest in our "Ask A Mechanic" series.

Q: Do I need to crack open the engine case to replace the countershaft seal on my dirt bike?

A: On most bikes it's just a matter of removing any cover that is over the countershaft (front) sprocket, removing the sprocket itself, then a spacer. After removing these components pry the countershaft seal out using a flat head screwdriver or similar. Older model dirt bikes and street bikes sometimes include a retaining ring along with and two 8mm or 10mm bolts behind the sprocket requiring removal, as well.

Oil leaking from behind the front sprocket indicates a bad countershaft seal

Tap the new seal into place using a hammer and a large socket and replace the rest of the parts. No case splitting needed.

Need a new countershaft seal? We featured the Hot Rods Countershaft Seal Kit as a product of the week.