Huh! Thank you guys so much. It seems that jetting is really a science. Hope my next bike will come with EFI :-). But on the other side the working principle of the carb is so interesting and without studying it I would have never learnt so much about the fuel system. I will try to implement all tips you suggested me and will keep you informed about results. My new jets will arrive in two weeks. The needle looks fine, so it will not be necessary to change it. One more interesting remark: Today it was raining here and the humidity increased to 72%. I went out for a ride and realized quite better reaction of the bike. Better acceleration and a bit more power on top end. This makes sense if I consider this article. It says that "as humidity increases, jetting will be richer"
JustRandy, thank you! I learnt many terms from this forum by reading it. But my spoken English is much worse. I would say more "eastern European" :-)))))

 

Glad I can help out a bit!

"Eastern European" <-- That's funny!

You guys impress me.... The only second language I know is redneck! [img]i/expressions/face-icon-small-happy.gif[/img]

That is a good article. It makes sense that as humidity goes up (meaning the amount of water in the air goes up), there is less oxygen in the "air" because water has displaced it per unit volume. So, as a result, there is too much gas compared to the amount of oxygen and your plugs end up black due to incomplete burning. (Ever notice a hot campfire burns without much smoke??? While a stack of wet leaves smokes like a tar wagon).

Pressure affects it too. If the air pressure is low, there is not as much oxygen in a unit of volume of air. So, the same thing results as before... Your plugs get black.

Temperature too. If its hot outside, the air will be thinner than if it were cold. Thinner air = less oxygen per volume = black plugs again.

So, if you went for a ride in high hunidity,,, that actually means you went for a ride in a low oxygen environment. And if your engine ran better, that means you wouldn't be getting enough gas for a high oxygen envirnoment (ie normal humidity). Therefore, you should increase the jet size to supply the gas needed in normal weather.

 

<div class="FTQUOTE"><begin quote>Originally posted by: JustRandy

And if your engine ran better, that means you wouldn't be getting enough gas for a high oxygen envirnoment (ie normal humidity). Therefore, you should increase the jet size to supply the gas needed in normal weather.</end quote></div>

Yessss!!!! That's exactly what I meant too! I hope piston rings and other stuff are o.k. and it is all about jets. I am looking forward for getting the new ones; hopefully they will help a lot. Until then I will ride only when it's raining :-)

 

If its not smoking, the pistons are probably ok. I would check the valve lash though.