walkman
Well Known Member
I spent a few hours yesterday trying to make sure my idle speed and mixture were set correctly. Starting with the various RSA manuals I removed the idle mixture linkage, set to the 2.5" nominal with the adjuster centered (it was 2.75"), and started to fool around with it. I ended up having to lengthen the link again slightly, and fool around a lot with the idle stop. This graph represents the best I was able to get it adjusted.
With the throttle on the idle stop, mixture full rich, it idles at 700 ±20 with the occasional "pop" in the exhaust. Occasional means very 3-5 seconds.
As I slowly pull the mixture back I get a corresponding slow drop in idle speed and an increase in the popping coupled with an increase in the variance of RPM. Idle speed drops off to 550 ±50. During this decrease it feels to me like the engine is too lean.
Then, right before ICO, I get an RPM rise to about 1,020 RPM, the RPM variance drops to ±10, the engine smooths out and popping stops. A minute further reduction in mixture and the engine shuts off.
My questions are this:
First, is this normal? I would have expected steady RPM until the rise, not a slow decline.
Second, the RPM rise at the end is about 300 above the initial idle speed, and 500 above the RPM just before the rise. This is much more than the RSA recommended amount (various sources put this at 10-50 RPM). Again, is this normal? I can lean it out a bit more, but it already feels too lean. Leaning it further makes the idle very rough indeed, with lots of popping.
Thank you
With the throttle on the idle stop, mixture full rich, it idles at 700 ±20 with the occasional "pop" in the exhaust. Occasional means very 3-5 seconds.
As I slowly pull the mixture back I get a corresponding slow drop in idle speed and an increase in the popping coupled with an increase in the variance of RPM. Idle speed drops off to 550 ±50. During this decrease it feels to me like the engine is too lean.
Then, right before ICO, I get an RPM rise to about 1,020 RPM, the RPM variance drops to ±10, the engine smooths out and popping stops. A minute further reduction in mixture and the engine shuts off.
My questions are this:
First, is this normal? I would have expected steady RPM until the rise, not a slow decline.
Second, the RPM rise at the end is about 300 above the initial idle speed, and 500 above the RPM just before the rise. This is much more than the RSA recommended amount (various sources put this at 10-50 RPM). Again, is this normal? I can lean it out a bit more, but it already feels too lean. Leaning it further makes the idle very rough indeed, with lots of popping.
Thank you
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