[indianFighter]

Is there any chance for oil to overflow from my crf250r if the bike overheats?

I was practicing zero turns involving hard first gear sprints and turns. When I pulled in I saw a few drops of oil below, it seemed like it was coming from one of the overflow pipes below the pegs. How is that possible?

[JimDirt]

Have you looked at your fluid levels since this happened ??

If so is one side overfilled and/or the other low ??

Has it done it since that 1 time ??

[Back2-2]

It is very likely from the breather tube off the valve cover. Condensation / oil vent mix.
The tube runs from the top of the valve cover, tee's into the gear case vent then over to he air box and down to the rear of the engine & pops out near the rear linkage. Stock it has a plug so the fluid builds up. Many people open the tube to allow drainage / breather out the tube end.

You also have a air box drain port that can drip oil if the filter gets a little too much oil when cleaning & oiling. It builds up and pools in the bottom of the air box & drips out on to the swingarm / suspension area.

Take a good look & trace it out.

[indianFighter]

Have you looked at your fluid levels since this happened ??

If so is one side overfilled and/or the other low ??

Has it done it since that 1 time ??

I checked and topped up; the clutch side used up about half a litre, the engine oil was fine. Haven't started the bike since then but standing still there is no leak anywhere, it just happened that one time when the engine got really hot.

What did you mean by one side overfilled?

[indianFighter]

It is very likely from the breather tube off the valve cover. Condensation / oil vent mix.
The tube runs from the top of the valve cover, tee's into the gear case vent then over to he air box and down to the rear of the engine & pops out near the rear linkage. Stock it has a plug so the fluid builds up. Many people open the tube to allow drainage / breather out the tube end.

You also have a air box drain port that can drip oil if the filter gets a little too much oil when cleaning & oiling. It builds up and pools in the bottom of the air box & drips out on to the swingarm / suspension area.

Take a good look & trace it out.

Man this sounds so complicated. I've looked externally and there is no leakage. Should I tear it apart and check?

[Back2-2]

Sorry - it is no big deal to check.
There is nothing to "tear apart". Take a look at the top / rear side of the valve cover for a black tube and follow it or look above the clutch side cover there will be a small black horizontal tube to follow. Both mate up together and exit with the rest of the bikes overboard tubes. They also mate to the air box unless you have eliminated that from OEM.

Just plop down & check out all the tubes under the bike. Touch them all & see which one is wet & what it is wet with.

[JimDirt]

Have you looked at your fluid levels since this happened ??

If so is one side overfilled and/or the other low ??

Has it done it since that 1 time ??

I checked and topped up; the clutch side used up about half a litre, the engine oil was fine. Haven't started the bike since then but standing still there is no leak anywhere, it just happened that one time when the engine got really hot.

What did you mean by one side overfilled?

What i meant was , like you mentioned the tranny side was low , so IF one side is low and the other side is overfilled that means either the Reed Valve (its a flapper valve just inside the left case) or a seal or gasket could have gone bad allowing oil to drain from one side of the motor to the other side (Honda's have completely separate oil for engine side and transmission side , unlike Yamaha's and other brands , it allows the engine side oil to stay cleaner longer because of the shavings usually accompanied from the clutch wearing and producing metal shavings , which is why the clutch side is usually dirtier than the engine side when changing oil)

So either the engine oil would be low and the tranny overfilled , or the tranny would be low with the engine side overfilled , that is why i asked if you noticed if either side was different than normal up or down in level , it would give a definitive answer to the issue if it was something serious

If the Engine side were to drain to the transmission side you would seize the crank or fry the cam , same goes if the oil evacuates the transmission , then you break the transmission gears or it locks up and breaks the main shaft and destroys the tranny and sometimes cases

I rebuilt a 09 CRF250R for a guy that had that vary thing happen to his daughter while she was racing , the engine locked up going over a 65 ft jump , she ate it bad by going over the bars ,when i tore the engine down the crank,piston bearings were toast and all had to be replaced , there was shrapnel everywhere , the second picture shows the Reed Valve i mentioned which caused all this

[Back2-2]

Mr. Jim, he stated the engine side was fine which shows that the shortage of the trans side did not migrate to the engine side.

I suspect he was banging those sharp, heavy leaning turns and spit trans oil out the gear case vent tube.
what do you think ?

That's one ugly pile of engine you have there !~ Ouch...

[indianFighter]

Yes guys, the engine side was fine. Only the tranny side was low. Bike was running fine after that too. I'll lay down and check out as advised.

I was doing 1st gear sprints and tight only left turns. Maybe that explains the tranny side venting?

[JimDirt]

Mr. Jim, he stated the engine side was fine which shows that the shortage of the trans side did not migrate to the engine side.

I suspect he was banging those sharp, heavy leaning turns and spit trans oil out the gear case vent tube.
what do you think ?

That's one ugly pile of engine you have there !~ Ouch...

Yea i understand what he said , i was just explaining the meaning to my questions to him prior to him mentioning that he checked the engine side oil level , so that is why i went in-depth about it , so he understood what "can" happen

and yes , if the engine side did not gain oil then i would say it evacuated out the tube ,as that does happen

And yea that motor was pretty bad , it scored the inside of the case where the crank counter weights ride , the shrapnel was everywhere the only thing salvaged was the tranny and Hinson clutch , the crank bearings , crank , rod, piston, were all totaled , it was actually Danny Smith's old Arenacross Championship bike , had some trick parts