Signs of right side seal failure?

[KX'er]

Other than gear oil loss (without an external leak), what are some signs of a right crank seal failure? I change my tranny oil every ride, so if it isn't leaking much, I'm not sure I would notice. I believe I may have a mild leak, but want to be sure before I go tearing everything apart..

I noticed that my bike smokes a bit excessively after I blip the throttle (for a few seconds, not while the engine is running), and the bike just sounds a little off. My pilot and airscrew are set correctly. My plug looks normal (black, but not saturated with oil). The only thing I can figure is that the crank seal is leaking a little...

Also, I haven't rebuilt the bottom end yet, and the bike is a 2000 KX310. How do I know when it is ready for a bottom end rebuild?
I've never done one before, is this something that I should send the motor to eric (gorr) for, I should I attempt it myself?
Thanks in advance.

 

[NO HAND]

I've learned with time that you can spot a left side air leak especially when you notice an aggravating lean condition on the low speed circuit. On a '95cr125 with a bad left side crank seal I ended up using a 65 low speed!? All this to say, Im suspecting bad a right side crank seal will have the opposite effect (sputtering rich) but still on the low speed circuit. I guess if you notice you need to go leaner and leaner on the low speed for no particular reason, it could well be the right side crank seal. Usually you can change it by just removing the casing on the clutch side and only unbolting the crank gear. After you have removed the gear, it will be easy to remove and install the new seal.

 

[KX'er]

That makes sense..

I heard on KX's you have to split the cases?? Is this true?

 

[Senior KX Rider]

Yes :(

 

[YZThumper]

I had a right side crank seal go bad on a YZ250. The bike had never fouled a plug in the 3 years I owned it. Then one day out of the blue, 3rd gear 3/4 throttle (thank god I was only trail riding) it fouled a plug.

Regardless of what gear or speed I was running at, I fouled about 5-6 more plugs. I cleaned the carb and messed with the jetting to no avail. It really had me chasing my tail.

Like I said, it turns out both of my crank seals had gone bad. Personally I sent my bottom end out to 2-Fast Racing, which is a good friend of Eric's. They did a great job. I always wanted to try that job myself, but I've never even seen it done before so I left it to the experts. Some day I'm going to buy a rat bike, just to learn how to replace bearings and seals and rebuild the bottom end.