Oil out of breather tube on YZ250F

[vancerd]

Yesterday I rode my new YZ250F on a race track for the first time. When I was done riding I noticed that the area around the left foot peg was wet. It looks like something (oil?) had been dripping out of the overflow tube (about 1/2 inch tube) that runs from the top of the engine, down the down tube, and ends right in front of the left foot peg.

What is the purpose of this tube. Is it an breather tube? Is it normal to see oil coming out of it? Is there anyway to put some coarse foam or something in the top of it to prevent oil from coming out?

 

[christopher]

Have you cleaned and oiled the airfilter lately?Sounds to me like filter oil dripping off the filter and running down the tube.

 

[Rich Rohrich]

A little oil from crankcase blowby is normal when the engine is revved hard. This is especially true when the engine is fairly new and the rings haven't seated completely.

You can use a small K&N crankcase vent filter on the end of the tube but it isn't really necessary. http://www.knfilters.com/vent.htm

 

[Boozer]

Originally posted by Rich Rohrich

You can use a small K&N crankcase vent filter on the end of the tube but it isn't really necessary. http://www.knfilters.com/vent.htm

i think they might be a good idea. after inspecting my valves recently, i found a fair bit of junk (dirt, sand) on the inside of my engine cover. the breather hose is the only way in.
i also have a bashplate, so maby that helped by keeping the crud near the breather hose.

 

[freddy_596]

My motorcycle did the same thing but when i started it and started do rev it up to warm it up tons of oil started coming out of my oil breather hose does anybody know why?

 

[rmc_olderthandirt]

If you are getting an excessive amount of air/oil coming out the breather vent it is an indication that your rings are shot. If the rings don't seal properly the cylinder compression leaks past into the crankcase, which then flows out the breather, carrying oil with it.

Was this a brand new bike, or just new to you?

If it was brand new then there is a chance that the rings just hadn't been broken in properly yet. It is not unusual that a new top end will have a fair amount of "blow by" until the rings get set in properly.

If it is just "new to you" and the engine has some number of hours on it then I would recommend that you plan on doing a top end rebuild before too long.

Rod

 

[jhuerta]

Make sure you didn't add too much oil. Some is going to come out but when you add too much it will spew it out. Use the bolt on the side of the crankcase to check the oil level.

 

[jhuerta]

If oil level is good then yeah you might need to do a top end. If the bike is new from dealer then take it back and have them look at it. If the bike is used then do a top end. If the bike is older than three to four years then do a top and bottom end. I just replace all the parts on my bike due to crank breaking and I cost me and extra 300-500. The piston and crank broke in my case. DONT LET THIS HAPPEN TO YOU!. Only if it's used and older. The piston compression might be pushing back into the crank case causing the oil to come out. Bad rings maybe.