Richen idle with needle or float?

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Deleted member 21174

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Before our last race (Blue slide) I had to turn the air bleed all the way in to get the kart to idle at all. To richen things up I dropped the float level .01" or so and it seemed to help. Is it also acceptable (and maybe better) to drop the needle down from P2 to P3 for this kind of situation?
 
So by dropped you mean went from say .800 too .810 ?
That for me would richen better then a needle adjustment .
 
As long as it doesn't stall out concentrate on racing mixture or just raise up the idle speed a bit as long as your clutch is not engaging. Idle means nothing out on the track. Make sure you have no vacuum leaks.
 
When you say air bleed you are actually referring to the idle air screw if turning it in increases Rpm. The air bleed screw will increase rpm to a point as you screw it out but it will affect fuel ratio as well. The engine should be capable of idling if the carb is setup properly but it is certainly not a necessity.
Clip 3
.870 float
1.5 out on air screw
This should allow the idle screw to be set without being all the way in.
Gary Lawson
Comet Racing Engines
 
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What rpm are you idling at? It will change a bit with weather. Don't make the mistake of trying idle too low. Been there and paid the price of kart stalling...
 
Did you drop the float or raise the float, when you say drop the needle you mean you drop the needle clip. Turning the air bleed screw all the way in should not improve idle, your carburetor needs attention. Where is the slide limit screw the idle speed screw set.
 
Questions: Why are you wanting to richen the idle?
I am more concerned with performance @ WOT.
As for idle, I really only care that it DOES idle, and doesn't stall on the track. Raise your idle screw a half turn and prblem solved in my opinion.


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Carlson Racing Engines
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When we got to the track I had to turn the air bleed almost all the way in to even get an idle. As the weather cooled even with it all the way in the engine would not idle - even in the low 2000s. The clutch is set to engage ~2800RPM or so (4 white springs - all I had left but arguably not a bad setting for a blue slide) so I did not want to turn the idle up to 2500 or 2700. I typically don't like opening up the carb at the track (I have fairly limited skills) but went with float height so I could get an idle and have enough room for more adjustment in case the air density kept going up. I was not looking for the world's best idle - just wanted it to idle so if my kid got spun out he would not be stranded and would have a chance to keep racing. It was not possible to set up the O2 sensor for this but I was curious of dropping the clip to the center slot (P3) would also have been a way to richen up the idle.
 
gary10 said:
Turn your air bleed in all the way and the engine will shut off.
Click to expand...
Not last week. That's why I adjusted the float (and thought about adjusting the needle). The air got dense fast ...
 
Have you taken the carb apart and thoroughly cleaned it? You probably have some crap in the pilot jet or a passage.
 
Chipg56 said:
Have you taken the carb apart and thoroughly cleaned it? You probably have some crap in the pilot jet or a passage.
Click to expand...
No - it's totally clean. Ultrasonic'd frequently and jets blown out. Going from .900 to .880 (or something like that) richened it up enough to run well. I was just curious if it's better t use the clip or the float to richen up as needed -
 
If you were way up around .900 I would say you did the right thing and more of the right thing is probably in order.
 
If all of a sudden it won't idle something went wrong.
If you make radical adjustments to fix it that is telling you something changed.
It's trying to tell you something else is wrong.
Most likely is the idle jet is plugged up. The hole for the fuel to go through is about .012"
Even with the best maintenance and care they get plugged up occasionally.
I always make sure i can see through the idle jet but it's wise to check it with an .011 of .012" gauge pin to make sure its not slightly restricted by something.
Unless they weren't set properly to begin with, changing the slide needle adjustment or the float level is a band aid for what ever is really wrong with the engine.
Notice i said engine. It could have a vacuum leak or a number of other problems giving you fits.
 
Hi Jim - thanks (as always). I do always look through the jet to make sure I can see light and I have gage pins (I bought extras - they are cheap - since I dropped one and could not find again they are so small). Usually the air is not as dense as 100% for us - it's more like 90% in the summer and even today the forecast is for 92% or so. We'll check everything again before we go back to the track. Thanks!
 
Unless you are in the middle of a tornado the air density in the mid west doesn't change enough to cause a serious idle problem.
 
I wish there was some safe way just to load the engine in my driveway or whatever (chassis rollers or something else) so I could lambda tune with an O2 sensor and generally mess around a little bit and get some data (no access to dyno where I live). After dropping the float .01" or so and putting the carb back on we ended up with the air bleed 1 3/4 turns out (that is where it idled best - I just use the Briggs guide since I don't have any other data).
 
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