Carburetor Tuning, to Rich or to Lean Condition

In previous stories I talked about carburetors Rich conditions and Lean Conditions, this is all fine of course if you know how to detect if your engine carburetor is set Rich or Lean.

To help with that, I will explain simple means to detect the setting of your bike. With a perfectly tuned engine you will get the power you need, it amazes me sometimes what people spent on kits to improve performance, while all they needed to do is get the settings right.

Okay that said what is a Rich Condition, while a black, scooty spark plug is a sure sign of richness, there are other indicators that are a bit subtler and better ways of dialing in the carburetor jetting.

If your engine responds crispy at low throttle when it is cold, chances are the main jet is one size larger than it needs to be. Assuming, of course, that the idle circuit is correctly tuned.

Poor fuel mileage is another sign of richness and because of the way most of us ride our motorcycles, that richness is unusually the result of a needle that is too small.
The color of the end of the exhaust pipe is a sign of mixture strength. Dark gray with some black is normal with today's lead-free fuels. If the exhaust color is black, chances are you can drop the size of the main jet.

It may be that you prefer a main jet that is slightly on the rich side of the correct range. A slightly over-rich condition lets a motorcycle accelerate better at low rpm.

So that was that about a Rich Condition and what about detecting a Lean Condition, a lean condition can quickly become a problem as the engine begins to self-destruct with detonation. Extremely with holes in pistons, burnt valves, and power loss top the list of reasons to make sure the jetting is on the money.

Pinging and knocking, poor acceleration, surging, and excessive popping during deceleration are all good signs of too lean a mixture. Also, if the bike seems to take a very long time to warm up or needs the choke longer than other bikes, chances are some tweaking of the jetting may be in order.
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Friday, 19 December 2008 @ 03:07 AM ICT
This is a truely awesome article.. Can't believe how much this helped me understand the problem.. I've been having exactly the same problems, in this exact manner, but never really could explain to any one over the Internet or forums.. it's probably the main jet.. or fuel running too rich, flooding the engine.. Thanks a million..!! Smile
I'll get on fixing my Kat 600 right tomorrow morning.. Smile