honda vfr 400 nc30 crankcase breather

[hondacrf250r]

could any one help, every now and then my honda throws oil out from the rear cylinders,it goes all over the exhaust pipe and smoke pours everywhere. im pressuming its this, do i need bigger crank case breathers. thanks.

[bikemonkey]

Are you putting too much oil in when you change it?

Are your current crankcase breathers blocked?

Could be a few things.

[hondacrf250r]

many thanks for your time but the oil level is just under the max, and the only breather i can find is the one from the rocker top to the air box, is there some more tucked away from view ??

[CMSMJ1]

If the one from the rear rocker feeds into the airbox, then where are you getting oil onto the rear pipes from? It should go into the engine and be burned...

Have a look see if you have a leak - pinched gasket on the rocker? Leak from somewhere else.

[VFRkieran]

Mark can it not go back out of the drain hose from the airbox? I cant remember if there is another one for excess oil from the breather to drain from, could have got on the pipes that way if so.

Only other thing i can think of is the spark plug drain hole, if the rocker cover gasket hasnt sealed right then you would have oil down there.

[Neosophist]

Bizzare.. no need to modify the engine, this is just bodging aroudn a fault instead of fixing the real problem.

Try and identify the source of the problem, where is the oil coming from exactly?

The crankcase breather goes into the airbox, it often gets a bit oiley from condensation but shouldnt be swimming in oil, if it were the crankcase breather belching out oil id imagine your carbs / airbox would be flooded.

There is as mentioned above a drainhole in the middle of each head that lets water out of the sparkplug holes should it get in there, the top of the engine is sealed with a rubber rockerbox gasket, they can go hard and brittle overtime and it is likely leaking from around here.

tank off and a good look should see where its coming from, wash everything down with some gunk type degreaser if you cant see and then warm it up while holding it and look for signs of leaking, dont need to wait until its gushing to find the leak.

[hondacrf250r]

many thanks to every one, there is no oil in the air box, or spark plug holes, when it chucks oil out once in while, it sounds as though you have a puncture then alot of smoke comes from the rear exhaust pipes and upon inspection oil all over the bottom of swinging arm at first i thought rear shocker had poped and oil shot over exhaust pipes, but it has done this 4 times now, the first time coming back from bridlington in the summer 2013, then about a month ago on a ride out then last week on a run out. its doing my head in im a cat mechanic for the past 11 years,so im thinking on the lines of the head gasket now,im off to kent on friday to pick up another engine then i can strip it and find the problem,i will never get rid of my nc30 i think they are a great little quick bike as before many thanks to every one for your help,looks like my fzr will have to come out for cadwell at the weekend

[CMSMJ1]

No worries dude.

not going to be a head gasket that burps oil out...

Hairline crack at sump plug? get it clean and take some pics of it after a ride...

[Neosophist]

as i said above, without a good de-grease and careful inspection you wont find the leak easily as oil tends to spread.

i would not strip an engine down as its costly without knowing forsure it needed it, could be anything from rockerbox gasket to hairline crack somwhere.

no guarantee youll find the issue if youstrip it and it can be costly to rebuild.

[VtypeV4]

as i said above, without a good de-grease and careful inspection you wont find the leak easily as oil tends to spread.

i would not strip an engine down as its costly without knowing forsure it needed it, could be anything from rockerbox gasket to hairline crack somwhere.

no guarantee youll find the issue if youstrip it and it can be costly to rebuild.

+1

I chased an oil leak on my FJ allover the engine and finally found it to to be a ropey rocker-box bolt oil seal. Took me ages!