WR400F Leaking Crankshaft Seal or Oil level too high - Possible Safety Issues?

Hi all,


Just noticed - during a cam-valve play adjustment-  that the area behind the cover from the engine case "CDI" side to get to the cranckshaft "turning" bolt was full with engine oil....

I wonder if this is caused by a leaking crankshaft seal or maybe due to a too high oil level.



In the work procedures I do not see the task to drain the oil before removing this cover. Cover picture is attached below or see link : 


(btw, this is not a picture of my bike, but one I found on google / this forum)



Oil came out the lower cover plate when I removed it.


The lower cover also has an o-ring. I therefore assume that a bit of oil behind is, is normal and expected...In fact there is a direct connnection to the distirbution chain "room" and therefore some oil will always enter this part of the case??? :confused:


But in my situation, a rather large amount was in it... ca.. > 100 ml i guess..- not sure, it was.before I closed the cover again...and drained the oil in the normal way.


So, my questions are:

  1. - Is it normal that this amount of oil is behind it (Wat should the oil level be) 
  2. - Could it be the crankshaft seal (leaking)? 
  3. - In case the crankshaft seal has caused it, how severe is this? Safety Risk of engine jamming?  :unsure:  So, must I replace it?


Replacing the Crank Shaft seal would mean almost compleet disassembly of the engine....   :facepalm:  


Thanks for sharing your experience!! or advise.... 







I am surprised no one responded to you.


Your left side of the engien is open to the entire crank sump, as is the right side. Nearly all modern 4S engines run the flywheel and stator in an oil bath (mist actuallyy, it is a dry sump engine). Do not run it with the TDC and crank plugs removed. Also, do not 'crank down' on them when tightening, just snug, let the orings seal it up


  1. If the bike has been sitting, all the oil will probably be sitting in the crank\case, you dribbles back in.
  2. There is no crank seal, no need for it
  3. No seal, to be concerned with


Follow your manual for checking the oil level. It must be done with a hot/warm engine. I check the oil at the end of a ride. As long as there is no puddle on the ground, I know the bike is ready to go next time.

Ah, ok... It all makes sense now...


Just spoke to a Yamaha mechanic in the shop, he said the same thing...


Thanks a lot!!!



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