Oil In AirBox

LilToker · Post by **LilToker** » 08 Oct 2009, 04:27

Hey guys,
I was going for a ride on my CRM250AR 99 the other day when i noticed the back tyre starting to slip out round some corners,
i pulled over to see what was wrong and there was oil leaking out of my air box breather hose onto my swing arm and back tyre. When i took the airbox cover off there was oil coming out of a little pipe in the top right hand corner of the box.

http://i36.tinypic.com/hsnw2h.jpg

Lucky the air filter soaked up most of it and none went into the engine, the only oil it can be is gear oil as my 2 stroke oil pump was removed so it cant be that. I tried to follow the hose where the oil was leaking out of in the air box and it leads into the engine near the exhaust manifold.

http://i33.tinypic.com/2who8xj.jpg

Does anyone know why my bike is doing this or the purpose of this hose at the top of the airbox? Im no mechanic and cant really afford to take it into the bike shop as they sting you for an arm and leg. I try keep my CRM healthly and fix it if i can so any help would be much apperciated.
Thanks

LilToker · Post by **LilToker** » 08 Oct 2009, 04:33

Also i have not filled up any gear box oil so it cant be thats its overfilled.

Post by **knackeredMk1** » 08 Oct 2009, 08:57

FMtB & Skidmark will probably know much more about this.

More modern bikes usually have a crank case breather tube that takes oil vapour from the crankcase into the intake system to ensure that these vapours are burnt and not vented to the atmosphere. However the crankcase breather tubes on other Mks of CRM are located on the top of the gearbox under the carb (don't know about ARs). Is this some kind of breather for the AR system

Post by **SkidMark** » 08 Oct 2009, 18:03

On my AR that hose comes from the rear of the engine - exiting just under the carb as KNMK1 says for the other MKs (I suspect yours does too rather than coming from the front near the exhaust manifold - there are so many hoses on AR's its hard to trace them - unless your bike is as stripped as mine is at the moment!!!). I would say it is the crankcase breather that routes to the airbox as KNMK1 suggested but FMtB will confirm...

Regards

SkidMark

Post by **Jonorow** » 08 Oct 2009, 19:23

the crankcase breather on the MK3 & AR comes up by the shock and feeds into the air box on the right side of the bike, remove the CDI and you should see it.

Post by **SkidMark** » 08 Oct 2009, 20:24

Jonorow wrote:the crankcase breather on the MK3 & AR comes up by the shock and feeds into the air box on the right side of the bike, remove the CDI and you should see it.

thanks Jonorow. That confirms its the breather then. If it definitely isn't overfilled (?) then the bad news is he's got high crankcase pressure... crank seals blown?

Regards

SkidMark

Post by **knackeredMk1** » 08 Oct 2009, 20:40

One other alternative is that the air filter has been over oiled. The oil then migrates to the lowest point of the air filter and drips into the airbox - this can look really messy.

Are you sure that the excess oil is coming out of this pipe

Just because it has a drop on the outlet does not mean the oil has come from here.

Are the filter oil and the gearbox oil the same colour

. Has air filter oil been used - not engine oil

Trying to be the optimist here - Otherwise it is probably as Skidmark has suggested

.

LilToker · Post by **LilToker** » 08 Oct 2009, 23:47

thanks for the replies guys,

Its definatly the crankcase breather as i went and retraced the hose and it lead to the top of gear box / under the carb. All these hoses can be confusing sometimes. The Air filter oil i use is a green spray (castrol air filter oil) and the oil found in the airbox was a brown oil the same as my gear oil (Castrol Gear Oil mtx), so unfortuntaly it isnt air filter oil :(.

I've gone for a few smaller rides and no oil has come up yet. If the crankcase seals are blown should oil be pissing out of the breather everytime i ride? The time i did find oil in the airbox it was long ride up at steep mountain with lots of corners (Mt glorious, Australia) and was working the gears alot so maybe i could of just over pressured it from that? Just trying to eliminate all possibilities before i go out and replace the crankcase seals.

Post by **knackeredMk1** » 09 Oct 2009, 09:29

If the seals are gone it will be blowing all the time. Have you tried to feel pressure at the end of the pipe when the engine is running & reved

It is possible that you fell off and some oil flowed out through the breather tube

I wouldn't start taking it apart until you are sure.

Post by **chris356** » 09 Oct 2009, 09:45

maybe too many wheelies whilst going up hill ? i would re check the level of the gearbox oil maybe there was too much oil in & the steep hills & hard accelaration caused the oil to vent up the breather.it as been known for people to overfill not by much but its very easily done
chris

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