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Author Topic: CB500 - Idles nice at 1800rpm, poor at 1000prm  (Read 838 times)

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Offline mroberts5

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CB500 - Idles nice at 1800rpm, poor at 1000prm
« on: September 18, 2011, 06:59:56 AM »
I have a 72 CB500 w/ pods and a 4-1 exhaust put on by the PO.  In nearly all regards it runs great.  I'm curious though - when I got it it was set up to idle at 1800, and it sounds pretty good here.  I recently did a vacuum sync, and it sounds even better.  I cannot get it to idle well at 1000rpm though.  Its very "lumpy" and generally doesn't sound good.  Before the vacuum sync it would die at 1000, now it'll hang on, but not happily.

Should I let it be at 1800 or is this a sign of a larger issue?
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Offline fmctm1sw

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Re: CB500 - Idles nice at 1800rpm, poor at 1000prm
« Reply #1 on: September 18, 2011, 07:09:25 AM »
1800RPM is awful fast IMO.  And with the 500 transmission already a soft spot, I'd do what I could to get it down.  At 1800, the advance should already be kicked (or kicking) in.  What does the timing look like before the advancer starts to work?
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Quote from: 754
Dude is that a tire ? or an O-ring..??

Quote from: inkscars
This is not a pod thread
This is not a #$%* on my vacuum gauges thread
This is a help or GTFO thread.

1973 CB350F
1973 CB350G
1975 CB550K
1983 GL650I
1973 CB750K3 (http://forums.sohc4.net/index.php?topic=92888.0)
1984 Kawasaki KLT-250 (AKA 3 wheeler of death)
1994 Honda TRX300
1999 Honda TRX250

Offline WarwickE36

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Re: CB500 - Idles nice at 1800rpm, poor at 1000prm
« Reply #2 on: September 18, 2011, 07:37:14 AM »
+1 for checking timing.  Sounds like it might be too advanced. 

If timing is spot on, your idle mixture may be way off, how do the plugs look?  Warm the bike up fully, pull the plugs, clean them or replace them with new, idle the bike for a minute or two then pull the plugs and inspect them.
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" Why does anyone get offended by what someone does to their own bike? I dont get it. "

You made me think about it after I cheered knowing someone else would like to know what these control freaks are up to.
 Every time any owner strips whatever precious Honda part the horrified purists parts go up in value. That's not the part that bothers them.
 What bothers them is they sat up late at night, their breast full of wonder and estrogen, unable to sleep, dreaming about their lovely darling and all her glory... and next thing you know someone else doesn't share their emotional deluge and their reaction is they must spread their mind museum as far as they possibly can, taking over as much of the real world as possible.

Drink fast, drive slow, but ride it like you stole it

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Offline Gordon

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Re: CB500 - Idles nice at 1800rpm, poor at 1000prm
« Reply #3 on: September 18, 2011, 08:11:56 AM »
Check the rpm with an external tachometer.  The stock tachs can be pretty far off. 
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Offline mroberts5

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Re: CB500 - Idles nice at 1800rpm, poor at 1000prm
« Reply #4 on: September 19, 2011, 06:01:15 AM »
Heres a video (no clue why I can't post actual links):

http:// youtu.be / QnjIwmNdXNc

Thanks guys.
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KingCustomCycles.com

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Re: CB500 - Idles nice at 1800rpm, poor at 1000prm
« Reply #5 on: September 19, 2011, 06:28:29 AM »
1800 is stretching the term "idle"  that is bumping the bottom of what I consider mid-range.  A vacuum leak is possible from cracked or misaligned boots.
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