egerkin

I have a quick question - I have recently rebuilt a Nikki Carb and in the process of reinstalling and tuning. I found the post below from Sterling and plan to follow this procedure.
I have also installed an EGT gauge and two K type probes into Racing Beat Headers about 5 inches from each flange. My question is what is the expected temperature of the exhaust gases with a properly tuned air fuel mixture? What temp would indicate that I am too lean and need to make the mixture more rich? Any help would be greatly appreciated.

Thanks - Eric
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Post From Sterling on Tuning the Nikki:

Idle SPEED screw...located under the linkage on the right side, very low, and hard to see. Requires a very long flatblade driver.

Idle MIXTURE screw...located dead center driver's side of the throttlebody (cast iron lower part of carb).

Run engine and get it warm. Fuel behavoir is subject to temperature. Tuning a cold engine does no good when it becomes warm.

You are tuning the IDLE only. Tuning the idle has no effect on anything over 2000 rpm.

Adjust the idle SPEED to anything below 1000 rpm.
If you cannot get below 1000 rpm, you have a vacuum leak...a cracked hose, dried-up gasket, that sort of thing- It's letting air come in to the idle circuit, and bleeding off the signal to the fuel source.

Next, adjust the MIXTURE screw by turning it clockwise till it wants to stall. This is leaning the idle mixture.

When it starts to "hunt", or stumble, turn it back 1/2 turn.

Redirect your attention to the idle SPEED screw, and turn it counterclockwise untill you are idling at 750 rpms.

Return to the idle MIXTURE screw, and adjust it the same way as before.

Check the idle SPEED again, and if necessary, repeat both steps.

Your done.

A vacuum leak will only cause an incorrectable high idle.
It will not cause a stumbling.
If you are experiencing stumbling during idle no matter how many times you adjust it, and if you can hear it as you slowly rev the engine, then this is most likely an ignition problem.

j9fd3s

iTrader: (3)

i would skip that procedure, the idle speed screw really doesn't need to be touched, and if you do touch it, no more than half turn either way.

the mixture part is correct, turn it until it runs the best, and then 1/4 turn leaner (will get better mileage).

not sure what the EGT will be like, most people have the probes 2-3" away, but your upper limit is about 1000c. idle should be about 450-550c, cruise is 700-800c and WOT should be about 850-950c.

with a catalytic converter, the cat needs to stay between 450-650c, so you end up running much richer, and WOT EGT will drop to ~700c.