Hi guys,

Would a very restrictive exhaust silencer cause the above symptoms? I can imagine that if pressure is building up in the exhaust then it "might" encourage blow-by and hence pressurisation of the crankcase?

If not what else might cause it? I am getting a fair bit of oil being chucked into my airbox

I don't have that much experience with 4 strokes, i'm a 2 stroke man at heart so any help would be appreciated.

Cheers,

Dan

Any other symptoms?
Oil level is correct?
Excessive blow by. Often caused by broken rings. A compression might would be the next step I would think.

Yes, make sure the oil hasn't been overfilled - the level should be with the bike upright not on the sidestand (you probably knew that).
Pull out the sparkplugs and check them, if one or more are oily then the rings are letting oil past. If you get smoke on start up then again suspect the rings.
It would need to ba a very restrictive pipe to do what you said ... check the exup valve is working (if you have one). You'll find it just back from where the 4 down pipes join on the sidestand side. There should be a chrome cover - take it off so you can see the pulley wheel then turn the ignition on / off you should hear the servo make a weep weep niose and see the pulley move right and then left. There are 2 prongs on the pulley, with the ingnition off they should line up either side of a hole in the housing.

Thanks for the replies!

The oil level is correct and doesn't appear to be burning it. No smoke on start up either.

EXUP valve is working and adjusted correctly.

I will check the plugs when I am next home :-)

Thanks for the heads up guys!

Dan

Blocked crankcase breather?
Take off the pipe at the top rear of the crankcase and make sure the pipe is clear and then that you can blow freely into the engine take off pipe, undo the oil filler cap first.
If the engine is not actually smoking when you're riding it it's probably not the rings or valve seals. Get someone to follow you to check for smoke properly as you might almost crash the bike trying to look behind while you ride.....
Give the air box a good clean along with all the pipework etc and see if it comes back as it might just be a load of shit that's accumulated over the years.

When i baught my 3tj i was having an oil leak from the airbox turns out the idiot i bought it from overfilled the oil i dropped 4.5 ltrs out of it lucky it didnt explode. Check oil level mate

Hi Guys,

Just an update on this. Fitted a simmi performance silencer off ebay (£77 posted, what a bargain brand new!) and the oil leak into the airbox has completely disappeared and the bike feels less strangled. I think the old restrictive silencer was causing the issue!

I cleaned the airbox thoroughly and after a thrash at a trackday the airbox and oil catch tank where dry as a bone and clean as a whistle. Very pleased.

Just need to get it back on the dyno and set-up now.

Dan

You shure nobody stuck a banana in your pipe ?

Good you got sorted.
Jeff at Consett does indeed make a very nice can.
He will also reskin or provide link pipes/repack or supply inlet/outlets.
Top quality trader.