High Engine Idle

csp1971

Well-Known Member
Messages
1,664
Location
Missouri
I'm trying to adjust the idle on my CY23 (Firehammer MT) engine. I have a DDM pipe on it.

This is what is happening, it starts up fine, second pull. The idle increases until the truck starts to roll. I have turned the H and L screws in, then for L went 1.25 out and the H 1.75 out. Now with the idle there is quite a bit of smoke. I richened it (L) a tiny bit but it starts to move again. I'm not sure really what to do with the idle screw. Do I turn the idle screw out to get the rpm's back down? Or in? Is it pretty sensitive to moving? What is the default setting for the idle screw?

(the throttle/brake servo setting is fine, there isn't an issue with the settings)

Almost a full tank of pissing around with this thing in high humidity and heat and I'm about to throw it!
 

cyclops1970

Well-Known Member
Messages
628
Location
Hamilton Ontario Canada
i copy'd this info for you from Dave Motors ..
How should I adjust the jets on a Walbro Carburetor (WA-167 / WT-603 / WT-668 / WT-257 / WT-813, etc)?
These carburetors require regular adjustment to ensure peak performance, and also to avoid an unsafe lean condition, which can prematurely damage your engine. If you find your top-end RPM's have fallen off a bit, or if you experience lagging or surging, it is probably time to re-adjust the carb jets. To ensure max performance and engine life, follow this procedure:
1) Locate the low and high RPM jets on the side of the carb - they are usually marked with a L and a H. Turn both jets completely CLOCKWISE ( to the fully closed position).
2) Rotate the Low jet counter-clockwise to 1 and 1/4 turns open.
3) Rotate the High jet counter-clockwise to approx 1 and 3/8 turns open.
4) Now, start the engine. You may need to turn the Low jet slightly one way or the other for the engine to start.
5) Adjust the Low jet as desired until the idle is where you like it. Turning clockwise ("CLOSING" THE JET) will produce a higher idle, and counterclockwise ("OPENING" THE JET) will produce a lower idle (and eventually flood and the engine will kill, if you turn it too far).
6) Open the throttle lever to full blast. Adjust the High jet until you get maximum RPMs. Note: this will probably be REALLY LOUD. Listen for the highest-pitched whine to tell you where max RPMs are hit. AFTER YOU FIND THE MAX RPM SETTING, TURN THE HIGH JET COUNTER-CLOCKWISE ("OPEN" THE JET) APPROX 1/16TH OF A TURN TO ENSURE YOU HAVE SUFFICIENT GAS/OIL MIX TO COOL THE ENGINE PROPERLY.

Note: The above are just general guidelines. You may need to adjust both the H and L screws once you begin riding, depending on engine loading, altitude, humidity, etc. The trick is to find settings that work well for you, and stick with them.
 

Timmahh

Bajastafarian Madnes
PLUS member
Messages
3,376
Location
Michigan
check your fuel liines for cracks leaks. typically by the carb inlet for the fuel flow into it.

a continues raise in idle may be air bubble seeping into the lines causing a slightly lean condition, thus raising the rpms. bigger bubbles means more air, so more of a lean condition, thus higher RPM. smaller bubbles will bring the rpm up for normal, or back down form a shot of larger bubbles.

if you have good lines and no leaks, start with the l at 1.4 or so, make it rich, but not overtly rich. lean the low till it idles up and isnt engauging the clutch, once you have it idleing ok, undo the idle screw to bring the idle back down, take it back until it not touching the stops. if its idleing really low, lean up the l a tad, if its idleing kinda high richen the l a bit. get it set on the low so it just idles and stay running, and now increase your idle set screw to a good idleing rpm. watch your plug for some low speed runs, and fine tune from there.

if your idle is erratc and all over the place thats a good sign of a fuel line air leak, or sometimes a slightly loose cylinder. if the cylinder get too loose, it will loose the prime in the motor and stall out. same will happen with a large air leak in the fuel line.

hth
T
 
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