Eureka!
 

My 2002 XT600E has been quite an unreliable beast and has frustrated me with two problems frequently debated on this forum - oil leaking from the air cleaner box and coughing and spluttering under load.
I think I've discovered, today, that these two problems are related! The oil from the engine breather coats the silly, miniature, paper air cleaner with a film, that's not easy to see, which traps dust and starves the engine of air just when you're trying to overtake a large truck up a hill into a headwind with a string of impatient cage drivers behind you.

Stuhowes, thanks for this post. Information like this can be very valuable to the next guy that has this problem.

How can you fix this? Do you know why your engine is blowing engine oil through the engine breather?

G600, there has been quite a bit on this forum about why XT600e's blow oil out of the engine breather. I think the consensus is that, as the oil pump gets old, it stops scavenging properly and oil sits in the sump instead of the reservoir. The dipstick then suggests oil is low so you top it up but you've now got too much oil and it blows out the breather into the airbox and then dribbles out a pipe, making the bike look like a 1960 British twin.
I've disconnected the engine breather from the airbox and routed it out past the back mudguard, with a little online filter to stop dirt being sucked back into the motor.
The proper solution might be to replace the oil pump and, perhaps, replace the stupidly small paper air filter with a foam one.

TTR600RE's have a foam filter not a paper one so they dont have this problem do they ?

The breather goes into the air box for environmental reasons. The oil vapor which is expelled through this is then sucked back into the engine to be burnt.

Obviously this does cause a film developing but as posted, only when you overfill your oil or run the engine really hot..

Why not remove the breather from the air box and run it into a catch tank (like a coke can strapped to the frame)

Simples ! :innocent:

Good idea, Tedmagnum.
I've been surprised that nobody else has made the oil breather - air filter - poor engine performance connection. But I suppose it is because, for many of you, "off road" means mud. Here, in South Africa, particularly at this time of the year, it means dust. And dust mixed with oil and sucked into fine mesh paper naturally makes it pretty impermeable.

hi there one of the first things i did on my xt was to diconect the breather pipe from the air box and vent it in to the air out of the way ,i blocked the hole in the air box up with a gromet . while the engine seems not to blow oil out even oil mist been drawn back through the intake i dont like . when i used to run my old z650 in winter the amount of smeg in the extended breather pipe i have on was unreal all caused through short jurneys with the engine not getting to temprature , so i dont want any oil mist or condansation mist in my airboxs . a couple of mates have jap inport srx600s very simuler to xt600e and both breath heavy but not in to the airbox, the airfilters for these were very costly so the lessan was learned quickly. zigzag

Thanks, Zigzag, for confirming my suspicions. I've been able to take my XT for only a short ride after the mods but it feels much peppier at full throttle. Got nearly 140k/h up an incline which is about 10k/h faster than before.

For 50000km I have ridden an asthmatic bike. Now she's cured. Hallelujah!