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Author Topic: Need help.....RPM question  (Read 1237 times)

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qcextreme

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Need help.....RPM question
« on: January 22, 2006, 03:07:48 PM »
The bike runs great, But at an idle the rpm start going crazy...When you let it sit there she sits at 1000 rpm and slowly start going reving up to about 3000 rpm and she stay there until you give her some gas and then she drops back to 1000 and slowly start reving back up....Any help would be great
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qcextreme

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Re: Need help.....RPM question
« Reply #1 on: January 23, 2006, 04:00:26 AM »
help
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Offline Bob Wessner

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Re: Need help.....RPM question
« Reply #2 on: January 23, 2006, 04:23:06 AM »
What year/model bike? What is the tune-up history on the bike? Any work on the carbs? Are all carb settings set to spec?
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Offline TwoTired

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Re: Need help.....RPM question
« Reply #3 on: January 23, 2006, 10:05:45 AM »
Given the very limited info on the problem, I suggest you look at carb sync and/or leaks in the runners between head and carb.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline jwalters

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Re: Need help.....RPM question
« Reply #4 on: January 24, 2006, 01:43:04 PM »
I would agree with Bob and TwoTired.

Start off by cleaning your carbs, incase incase you havn't already. (didn't say in the post so I will assume they are dirty)  This fixes most of the problems.

And as TwoTired mentioned, go over your intake manifold boots, to make sure you don't have an air leak.  Look for any small cracks, you can use WD-40 or something else to find bubbles in the rubber.  This can cause your symptoms.

Sounds obvious, but double check that your throttle is returning ALL the way.  This will insure your not getting some sort of throttle creep.

Finally, if these simple things don't fix it, double check your timing.  If your advance is way out of wack, you might experience similar issues (just a guess though).
-j
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1997 Suzuki Bandit 1200S
1972 Honda CB 750 K2 "Cafe Racer"

Offline n9viw

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Re: Need help.....RPM question
« Reply #5 on: January 24, 2006, 01:47:07 PM »
+1 on all the suggestions- check timing, valves, check for air leaks, and make sure the carbs are properly synched.
My 550k did the same 'wandering idle' thing until I bench-synched them with a pair of 1/8" drill blanks. That got me in the ballpark, so the wandering went away, but the performance (particularly off-idle) just wasn't there. I've since purchased a set of merc sticks, and when the engine is done with its overhaul, I plan to do it up right this time.
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Nick

'76 Honda CB550k
'73 Honda CB750k

whoismattclark

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Re: Need help.....RPM question
« Reply #6 on: May 03, 2006, 09:42:07 PM »
I am having this problem, I have another post running describing the issue:

http://www.sohc4.us/forums/index.php?topic=9129.0

What was the result with your problem?  I thought carb syncing would solve everything, but it looks like I have deeper rooted issues.  I can't find any air leaks.  Boots and manifold look fine, they were used on another engine without issue.

Any more advice for someone who has tried finding air leaks, cleaning the jets, and syncing the carbs?

thanks,
MDC
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