Author Topic: Does ambient temperature alter idle level?  (Read 589 times)

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Offline gmoneymagna

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Does ambient temperature alter idle level?
« on: August 01, 2019, 08:17:20 AM »
Recently removed the carbs on my CB650 cleaning (new to carb work) and just making sure I'm not missing something. To start this post off, the bike runs better than ever with strong power and good exhaust sound.

I adjusted the idle temperature the other week to 1100 rpm after I put on the carbs when the bike was fully warm, but it was ~100F outside. Now in typical midwest fashion, the temperature is ~60 in the AM. I notice at cooler temperature my idle slightly increases from 1100 +/- 100 to 1200-1250 +/- 100 (after the initial warm up) with no notable change in performance. The idle will go slowly back to 1100 as the bike warms completely up and the ambient temperature increases.

Just curious if the cooler air temp causes a leaner mixture that causes idle to slightly increase, and to fall back to normal when the carbs and air surrounding the intake heat up and enrich the mixture. Is this something that happens? Thanks for the continued advice everyone!

Offline evanphi

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Re: Does ambient temperature alter idle level?
« Reply #1 on: August 01, 2019, 12:10:10 PM »
With that much range in your measured idle speed... I wouldn't worry one bit about it. How are you getting this measurement? Unless it is a laser tach or something, the variability you mentioned could just be from the stock tach.
--Evan

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Offline spotty

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Re: Does ambient temperature alter idle level?
« Reply #2 on: August 01, 2019, 05:21:20 PM »
colder temps equal denser air so in theory your bike is getting more actual molecules of air so yes, it is running a little leaner but as per above nothing to really worry about
i blame Terry