Author Topic: rich at 1/4 throttle (Read 5910 times)

goatracer · « **on:** October 16, 2016, 06:32:01 PM »

im a bit rich at 1/4 throttle right now my current set up is a 370 race gas with a 38 air striker 58 pilot dgh second from full rich and a 180 main what cn i change to lean 1/4 throttle just a bit

hickwheeler · « **Reply #1 on:** October 16, 2016, 06:40:12 PM »

That seems like a huge pilot. You could also drop the needle

goatracer · « **Reply #2 on:** October 16, 2016, 07:01:16 PM »

i did lower the needle one spot today it was full rich, this did help some

Jerry Hall · « **Reply #3 on:** October 16, 2016, 07:05:05 PM »

Are you sure the problem you are having is occurring when the slide is 1/4 open or when the throttle lever has been moved 1/4 of its total travel. In order to determine what circuit is responsible for your problem, you have to accurately determine where the slide is positioned when the problem is occurring.

Where is your idle stop adjusting screw set? If it is turned in all of the way and the air screw is 1.5 to 2 turns out there is a good chance that the pilot jet is too large. I usually end up with a 45 to 52 pilot in similar setups. If the idle stop screw is not turned in all of the way and the air screw is somewhere between 1.5 to 2 turns out I would install a DGJ or DGK needle. The diameter of the straight portion of the needle and slide cut away is what controls the fuel flow between the needle jet and needle from zero to almost half throttle. Moving the clip a position will not change the mixture at 1/4 throttle!!!!!!!!!!! Moving the clip on the needle does not change the mixture until the throttle is open enough for the taper to cause a change in fuel flow. Put a mark on your needle where the taper starts. Remove the carb from the reed. Open the throttle and observe when the mark becomes visible. This is the throttle position where moving the clip will change the mixture.

goatracer · « **Reply #4 on:** October 16, 2016, 07:09:58 PM »

idle speed screw is almost all the way in, it does not seem to like a pilot less than 55

hickwheeler · « **Reply #5 on:** October 16, 2016, 07:12:08 PM »

That seems to be the way pwk end up with the idle screw

goatracer · « **Reply #6 on:** October 16, 2016, 07:13:48 PM »

my elevation is around 700 foot above sea level

hickwheeler · « **Reply #7 on:** October 16, 2016, 07:15:52 PM »

Quote from: Jerry Hall;70191

Are you sure the problem you are having is occurring when the slide is 1/4 open or when the throttle lever has been moved 1/4 of its total travel. I order to determine what circuit is responsible for your problem, you have to accurately determine where the slide is positioned when the problem is occurring.

Where is your idle stop adjusting screw set? If it is turned in all of the way and the air screw is 1.5 to 2 turns out there is a good chance that the pilot jet is too large. I usually end up with a 45 to 52 pilot in similar setups. If the idle stop screw is not turned in all of the way and the air screw is somewhere between 1.5 to 2 turns out I would install a DGJ or DGK needle. The diameter of the straight portion of the needle and slide cut away is what controls the fuel flow between the needle jet and needle from zero to almost half throttle. Moving the clip a position will not change the mixture at 1/4 throttle!!!!!!!!!!! Moving the clip on the needle does not change the mixture until the throttle is open enough for the taper to cause a change in fuel flow. Put a mark on your needle where the taper starts. Remove the carb from the reed. Open the throttle and observe when the mark becomes visible. This is the throttle position where moving the clip will change the mixture.

Thanks for your input. Didn't realize needle wouldn't change at 1/4 throttle. I would listen to Jerry. He is far more knowledgeable than me

hickwheeler · « **Reply #8 on:** October 16, 2016, 07:18:36 PM »

Have pressure tested you motor. To see if you have air leak.

goatracer · « **Reply #9 on:** October 16, 2016, 07:56:38 PM »

no i have not

Jerry Hall · « **Reply #10 on:** October 16, 2016, 08:02:52 PM »

Quote from: goatracer;70194

my elevation is around 700 foot above sea level

The pilot jet for 700 ft will be good for sea level to about 3000 ft.

Jerry Hall · « **Reply #11 on:** October 16, 2016, 08:04:13 PM »

Quote from: goatracer;70192

idle speed screw is almost all the way in, it does not seem to like a pilot less than 55

What running symptoms do you experience when you go leaner than a 55 pilot jet

goatracer · « **Reply #12 on:** October 16, 2016, 08:09:54 PM »

very hard starting and it does not pull as well

Jerry Hall · « **Reply #13 on:** October 16, 2016, 08:15:20 PM »

Quote from: hickwheeler;70193

That seems to be the way pwk end up with the idle screw

If the slide is open more than about 2mm it will usually take a large pilot jet to give the right idle speed.

Most of these carburetors need the slide to be open 1 to 2 mm to allow the proper air flow to make the engine idle at the right RPM when the idle mixture is correct.

Jerry Hall · « **Reply #14 on:** October 16, 2016, 08:20:00 PM »

Quote from: goatracer;70200

very hard starting and it does not pull as well

Does activating the choke button improve starting when you go leaner on the pilot?

Does going leaner on the pilot cause the engine to have a hesitation when suddenly opening the throttle