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Author Topic: CB550K Hunting RPM  (Read 1726 times)

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Blackhorse

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CB550K Hunting RPM
« on: November 02, 2005, 07:51:07 PM »
I've got a 1974 CB 550K that wants to rpm hunt while idling. Is this normal, or do I have some sort of problem with the ignition advance?
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Buffo

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Re: CB550K Hunting RPM
« Reply #1 on: November 02, 2005, 08:04:39 PM »
are the airbox and filter, exhaust and ignition all stock?
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Ben

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Re: CB550K Hunting RPM
« Reply #2 on: November 02, 2005, 09:47:32 PM »
Sounds lean to me, try messing about with the mixture screws. Failing that, pull the carbs and give them a clean and also check that there are no air leaks where the carbs join the head. This can be done by spraying a little aerostart or wd40 on to each manifold in turn. If the revs rise, then you have found a leak. Be careful not to set your bike on fire while doing this!!!!!

I think it is unlikely to be anything advance related.

Cheers.
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Offline TwoTired

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Re: CB550K Hunting RPM
« Reply #3 on: November 02, 2005, 10:58:41 PM »
Lots of run problems that develop with the CB550 are solved with a complete and thorough tuneup.  This should be done every 3000 miles anyway, but certainly before any carburetor adjustments are made.

If the tuneup doesn't cure the problem then it's probably time to sync the carbs.
Have you checked for fuel contamination?  Or, air leaks between carb and head.

Also, unless you mention changes, we always assume a stock configured bike.  Modified bikes frequently need different adjustments.

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 Jay B

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Re: CB550K Hunting RPM
« Reply #4 on: November 03, 2005, 03:43:31 AM »
I'd second Two Tired's guess about a carb synch. Maybe unrelated, but BMW Oilheads like my other bike will hunt or surge something terrible if the throttle bodies aren't synched perfectly. To do a really good job you should do a valve adjust first as this will affect synch slightly. BTW, on BMW forums the surging issue is the "thread from hell" worse than tires, shocks, and oil combined! :o
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Jay
'77 CB550K
'74 CB350F cafe
2001 Road King
'73 CB175

MetalHead550

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Re: CB550K Hunting RPM
« Reply #5 on: November 03, 2005, 05:58:42 AM »
Id add cam chain and valve adjustment.  Not hard.  The first time I adjusted my valves I made the mistake of setting the valve clearances first, then adjusting the cam chain slack.  Threw off the settings...does that make sense?  After it warmed up it did the same thing, reving a bit by itself.  The next day when it was dead cold I checked the clearances again and found some to be to tight and others too loose.  Readjustment cured the problem.  Someone correct me if Im wrong about that.  Not saying that IS your problem, any of the replies could be it.  So just do them all when you have time since its regular maintenance type stuff and your bike will love you for it.  Later.
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Offline Gordon

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Re: CB550K Hunting RPM
« Reply #6 on: November 03, 2005, 06:14:35 AM »
Yep, carb synch.  But that's the last thing you do after a full tune-up. 
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Blackhorse

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Re: CB550K Hunting RPM
« Reply #7 on: November 03, 2005, 01:55:44 PM »
Thanks for all the input Gentlemen. A tune up has been accomplished and timing is spot on. A carb synch has not been done nor a search for air leaks so that will be the next set of tasks
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