blown valve cover gasket - 2009 Honda CRF450R

[jeffmort]

Today after riding I noticed that my motor was covered with oil and found that the valve cover gasket was blown out (a 1" section protruding out between the valve cover and the head on the front side).
My bike was set up by the previous owner to have the valve cover breather hose draining directly through a single vent tube without a plug on the end - the stock vent hose is set up with a plug on the end of it (read below). I have been riding the bike with this set up for months without any issues. The problem I had with the blown valve cover gasket occurred after I changed the vent tube set up back to stock.

The stock vent tube set up comes off the valve cover port and meets up at a "Y" junction with another vent tube that is coming off the air cleaner box. These two vent tubes meet at the "Y" and collect into a single vent tube that proceeds down to a spot near the crank case located just inside of the front sprocket. The end of this tube is closed off with a plug that is held in place with a pinch clamp. Per the owners manual, you are supposed to remove this plug periodically to let any built up fluid drain out.

For whatever reason, I decided to take the vent hose set up from the modified set up (single vent hose without a plug) to the stock set up (two vent hoses merging into 1 hose with a plug). The first ride after I changed things back to stock is when I had this problem.

My question is: What could have caused this to happen? My guess is that because the end of the tube had a plug in it, the back pressure from the plugged tube caused the gasket to blow but I would also think that the stock set up should work just fine. I will taking it back to the custom set up.

Any thoughts would be appreciated.

Thanks.

 

[Ol'89r]

The stock vent tube set up comes off the valve cover port and meets up at a "Y" junction with another vent tube that is coming off the air cleaner box. These two vent tubes meet at the "Y" and collect into a single vent tube that proceeds down to a spot near the crank case located just inside of the front sprocket. The end of this tube is closed off with a plug that is held in place with a pinch clamp. Per the owners manual, you are supposed to remove this plug periodically to let any built up fluid drain out.
.

Check the tube where it goes into the air box. Chances are, that fitting in the air box is clogged.

 

[IndyMX]

All of the aftermarket kits that I have seen for this conversion have involved a plug to close off the fitting in the airbox. If you don't take that off, it will definitely be blocked.

 

[jeffmort]

I checked the air box port and was intentionally plugged off - you guys were both correct.
I spoke with the Troy Lee mechanic that serviced the bike (it was a Troy Lee Designs team rider's practice bike) and he confirmed that he had plugged off the airbox port and ran a single breather/vent hose directly from the valve cover port.
Lesson learned: sometimes if if ain't broke, don't fix it.

Next question: Obviously I lost oil during my 1.5 hour ride yesterday. When I got home I drained the oil that was remaining in the crank case - it only had approximately 175 cc's of oil in it (should have had 600 cc +/-). When I removed the valve cover the valves, chain, etc. were all wet with oil (in other words it was not dry which I assume is good), also there was oil in the oil filter chamber which is also good I assume. The bike was not making any funny noises or acting abnormal at the time I shut it down so that is a good sign.
My question is: while I am replacing the valve cover gasket (and checking the valves clearances while I have the cover off) what else should I be looking for as it relates to possible damage/wear from having low oil in the bike?

Thanks again.

 

[IndyMX]

My question is why did you want to return it to the stock setup?

The idea of that mod is so that whatever oil might come thru that vent doesn't get into the intake tract..

I'd look for any spots on the cam that look "hot" or look rough.. I'd guess that if the clearances on your valves are ok, you may be fine. Just pay CLOSE attention to how the bike sounds from here on out.. If you not a change in the sound, investigate quick.

 

[jeffmort]

My experience from working on classic cars from the 60's-70's is that using aftermarket parts and mods is often times a net negative and that running stock OEM parts is rarely a bad thing.

With this concept in mind, I changed it back to stock. The other reason is that I like knowing how/why things work, I like performing maintenance on my bike and I was running out of things to "fix" so I changed it back to what I thought was stock. I was unaware that blocking off the air port is a typical mod that people perform. Now I know.

I will look for any hot spots on the cam and other components and replace as is needed.