Question for Carb Guru

[chumbiwumba]

I got my Kawa 650sx running today. At first it didn't want to stay running so I started turning the low speed mixture out from the initial setting of 1 turn out. It ran but somewhat irratically until I started turning it in again slowly.

My question is about the basics of this operation. I understand that turning it in leans the carb but what exactly am I to look for? As I lean the engine it starts to run faster. Is there a break point or change that I should look for when adjusting the low speed jet?

I have looked in the stupid Clymers manuals and all they tell you is how to disassemble and reassemble them.

Any light you could shed on this would be much appreciated.

[chumbiwumba]

Re: Question for Carb Guru

I wanted to add that I just rebuilt the carb and replaced the needle. Tested it for leaks and there were none. The popoff pressure measured with a Mikuni gauge was over 40 PSI which struck me as being a little high? The carb was acually immaculate inside, though I clean it anyway.

I didn't replace the seat because it appeared to be pressed into the base plate. I guess you have to replace the entire plate or press it out?

I cleaned the tank, filter, lines, gas valve and check the pump as well. Compression is 170/172 PSI. Plug gap .028"

[dowkk]

Re: Question for Carb Guru

You want the highest speed. As you go too rich or too lean the speed will drop. You want to turn in or clockwise ( lean ) until speed drops slightly. You want to go out or counterclockwise ( rich ) until speed drops slightly.

Be patient and turn the screw no more than 1/8 at a time. When you turn it wait a few seconds for the adjustment to be felt by the engine.

Try going both rich and lean until you have a feel for where the middle is. If the idle gets too fast turn out your idle stop screw until the idle is back in range.

Once you have a good feel for the mid point you are ready to make the final adjustment. It is never good to be lean on a 2 stroke so the final adjustment should be toward rich. Start with what you feel or hear is the best idle. Slowly turn the screw out or counterclockwise until the idle just starts to drop. Turn back in just a bit toward best idle. That's your setting.

What you are shooting for is the highest / smoothest idle without being rich or lean and if not sure it's always best to err in the direction of rich.

Too rich ruins spark plugs, too lean ruins engines.

[chumbiwumba]

Re: Question for Carb Guru

Thanks Dowkk. This makes perfect sense. Its almost like tuning a guitar. Appreciate your detailed response.