Oil leak, but where from?
 

Hi, my bike seems to have a sprung a leak! im in the proces of taking it apart in my garage, some oil was in the airbox, not enough to have leaked out though. know some numpty had overfilled it before, has anyone had this before or does anyone know any places that it's most likely to be leaking from? Thanks, Matt

Is is thrown into the airbox by the SV's internal pressure at high revs. This is supposed to happen and at lower revs it drips back down again.

If its excessive the chances are the engines been over filled.

A bit of oil in the airbox is nothing to worry about!

A lot of oil on the drive when on its stand is though! Taken the airbox off and it looks like the rear gasket has gone, dont know what it's called, i foolishly gave it a wipe before taking a picture so anyone could confirm it :roll: Anyway, on with the pics. This one worries me with the amount of oil around the top of the carb and the general crap on the hoses and stuff.

http://www.bikepics.com/pics/pics/su...ics-406605.jpg

And this one is the side where i suspect it's leaking, but the oil is running over the clutch cover, and i wouldnt expect it to do that if it was from the rear cylinder, but the front pot doesnt have a spot on it.

http://www.bikepics.com/pics/pics/su...ics-406604.jpg

It's definately losing oil rom soemwhere, the level is very slowly going down

I seem to also be loosing oil, in 1000 miles from england to spain the oil level had gone from full to not showing on the sight glass when level.

Dont know where it went but topped it up and bike seems fine anyway. Probably the high heat and the bike running at 80 average all day long.

When the engine is firing, some gas leaks past the piston rings. That's perfectly normal and indeed the ring pack is designed to control the "blowby" to manage the pressures behind and between the rings and thus control the gas leakage and oil consumption.

The Blowby is vented from the crankcase into the airbox so that the pressure in the crankcase doesn't increase and the gases are consumed by the engine to control emissions (legal requirement).

Blowby is normally less than 1% of the air consumption of the engine typically.

Because the gases pass through the crankcase it unfortunately picks up oil droplets which need to be separated out again and returned to the sump. Unfortunately breather separators are never 100% efficient, so inevitably some oil gets "carried over", which is what you see in the airbox. A light film is normal, swimming in it isn't.

3 things have a direct influence on oil carry-over. First the amount of blowby, second the oil level (which affects the amount and size of oil droplets in the crankcase), and third the engine speed.

If you know your engine has been overfilled significantly, I'd suggest simply clean out the airbox (and the oil on the outside of the engine) and start again, set the oil level to mid-way in the window, and monitor the situation carefully.

Check that the 2 breather hoses from the engine to the airbox are clean and in good condition with no cracks/splits.

The rubber carb couplings should stay in the airbox when removed (if the clip is undone!), I notice one is still on the carb in your pics. Is it in good condition?

Blowby and oil consumption depend how well the engine was "run-in" originally, and what sort of life it's had.