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Author Topic: Is high idle rpm harmful?  (Read 1470 times)

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Offline Jasondo

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Is high idle rpm harmful?
« on: August 14, 2013, 05:01:43 PM »
Why does Honda recommend 1250 rpm idle for my 400f. Why not 1400 or 1500 rpm. It seems to idle much smoother there...  Is it harmful to run the idle higher than suggested?
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Offline david 750f

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Re: Is high idle rpm harmful?
« Reply #1 on: August 14, 2013, 05:05:49 PM »
How are you checking your idle speed? The stock tach's can be inaccurate.
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Offline TwoTired

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Re: Is high idle rpm harmful?
« Reply #2 on: August 14, 2013, 06:08:38 PM »
The engine idle is most used when the bike is stopped.  Stopped means no airflow over the cooling fins.  High idle, speeds the time toward overheating the cylinders.

If it doesn't idle at properly at 1250 RPM, there is something wrong that needs fixin'.
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Offline lucky

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Re: Is high idle rpm harmful?
« Reply #3 on: August 14, 2013, 11:00:43 PM »
Quote from: Jasondo on August 14, 2013, 05:01:43 PM
Why does Honda recommend 1250 rpm idle for my 400f. Why not 1400 or 1500 rpm. It seems to idle much smoother there...  Is it harmful to run the idle higher than suggested?

It will be harder to get the bike in and out of gear with the engine rpm too high.
It is also just disturbing to hear it.
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Offline LesterPiglet

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Re: Is high idle rpm harmful?
« Reply #4 on: August 15, 2013, 03:28:51 AM »
I haven't had a tacho for years so have no idea what my bike idles at. I just set it as low as possible without the engine trying to rattle to death.
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Offline bjatwood

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Re: Is high idle rpm harmful?
« Reply #5 on: August 15, 2013, 05:20:56 AM »
My K3 will idle below 1K also, but I do not like the way the engine sounds either. Like it's about to cough up a lung or something...LOL 1200 is much smoother and quieter....
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Offline 750K

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Re: Is high idle rpm harmful?
« Reply #6 on: August 15, 2013, 02:51:30 PM »
I just set mine to where it sounds and idles the happiest, last time I had a timing light on it I noticed my tach is a bit on the high side so I defiantly don't go by it 100%. It's not off by much, so I go by sound and feel a bit more.
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Offline evanphi

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Re: Is high idle rpm harmful?
« Reply #7 on: August 15, 2013, 02:59:22 PM »
My electronic tach says I idle at 1K. Sounds purdy.
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Offline goldarrow

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Re: Is high idle rpm harmful?
« Reply #8 on: August 15, 2013, 04:02:00 PM »
my 550 bike has a 650 tach on it due to camshaft swap, but it idles smoothly at 1000 rpm....i guess the idle rpm has to do with how the bike is tuned?
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Offline lucky

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Re: Is high idle rpm harmful?
« Reply #9 on: August 16, 2013, 11:28:07 AM »
Quote from: rotortiller on August 15, 2013, 02:19:38 AM
I doubt a higher idle will hurt anything. I run my CB750 at 1300, always have since it is much more quite.I do this even after a carb sync. The book says 900 or so but everyone I know runs 1200 and above for the 750. I can run it at 900 but I don't like how they sound at low idle rpms.

The 350- 400F is spec'd at 1200 rpm.

If it's really hot out like 30C or so I will kill the engine at a extended stop lights, some of the Fergy guys so the same thing (if at 900 idle I'd do the same thing). My bike does not need any repairs, has been at the higher idle for years with more to come so don't believe everything you read in here. Many different bikes idle close to 1.5 grand. Think about the Fergy with it's unexposed aft cylinder, now that's hot!

RT

There was a SAE paper written on this subject.
It basically said that if you had two engines at cruising speed and one was running 1,000 rpm faster than the other that the amount of wear between the engines  was found to be negligable.
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