Excessive smoke from exhaust?

[mikesaa309]

Hi,

I'm new to BCF, sorry if this is in the wrong place.

I have a 2009 CBF 125 thats done 40,000 miles (i ride alot).
Recently there has been a lot of smoke coming out of the exhaust and soon became apparent that something isn't right. So after looking on the internet and haynes manual it's obviously burning oil (smoke colour is blue/grey colour).

The possible causes i'm aware of are:
Piston rings (oil control ring)
Valve seals or stems
Overfilled with oil
clogged crankcase breather hose

I checked oil level thats fine, checked the crankcase breather hose and thats about 1/4 filled with white sludge and there is some in the air box. Replaced the air box with one of a crashed CBF which i brought of ebay as my engine had piston slap due to really hot weather so i replaced the engine with the crashed one (engine was still fine but had been thrashed by previous owner and the main bearing went at 10,000 miles. My original engine lasted 38,000.)

So with a clean air box and i cleaned the hose out, i put it all back together but it's still smoking although after i rode out on it for around 30 mins and took it off again i noticed the same white sludge in the hose)

The thing i don't understand is that the bike still performs as well as it always has done despite the millage and the smoke so i can't be loosing compression and also the spark plug is the perfect colour and isn't oily or sutty. Could anything else cause the bike to smoke such as a faulty fuel management system. I just want to pinpoint the problem as best i can without taking it to a garage and without stripping the engine out. Obviously once i've eliminated all other possibilities i'll have no choice but to strip the engine.

Information about the bike if it helps:

Air cooled, single cylinder, 125cc engine.
It's fuel injected

Sorry for the long question but just wanted to clarify what i've checked so far etc.

[Pete.]

Wear is measured in miles not years so your 40k miles is quite significant. I would look at buying a complete unit from a crashed low-mileage bike based on the mileage and the symptoms.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[SQL]

[Kickstart]

Hi

A bit of white sludge is not unusual. At this time of year moisture in the air will condense in the engine and land up getting trapped in the flame trap in the breather. Short journeys won't help (although you will likely get oil that looks like a white emulsion as well).

The oil control rings are normally further down the piston from the upper rings that are there to provide compression, so a check of compression isn't a 100% guide to know if the rings are worn. Worn valve stem oil seals will probably be most noticeable when accelerating after gently slowing with the throttle closed for a while.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing