Hendrik, first thing I'd do, is have the appropiate documents at hand dealing with your specific model.
They're here:
Parts List:
https://www.honda4fun.com/dwnload/Part-List/CB500/CB500-K3-CB550-K3-K4-Parts-List.pdfBTW, p.4 informs you, yours is a CB550K3, probably the -G model.
If you need the
Owner's Manual, it is here:
https://www.honda4fun.com/dwnload/Owners-Manual/CB500K-CB550K-Owners-Manual.pdf Remark: do
not try to adjust the camchain tensioner as described in this
particular Owner's Manual; you will never get it right that way. Do it as described elsewhere, so
no running engine.
The
Shop Manual CB500-550, which includes an addendum covering your model, is here:
https://www.dropbox.com/s/88zdzlj8olqi8pl/Honda%20CB500_CB550%20%20Four%20Service%20Manual.pdf?dl=0Best tool for the sparkplugs is the Honda one. If not in the toolbag under the seat, it is still available for a reasonable price at
https://www.cmsnl.com/honda-cb550k3-four-germany_model14674/wrench-plug_89216323000/This is what has worked best for me. Before I mount a sparkplug, I screw the little ferrule on top, some non OEM plugcaps require, but... just a few turns. Now press the plug in the Honda tool, so the rubber, high inside that tool, will have a firm grip. The sparkplugs hexagon is now exactly where it should be and the whole combination is stiff and easy to work with, meaning the plug will not fall out. Screw the sparkplug down and tighten. Withdraw the plugtool and then simply remove that ferrule again. On
removing the sparkplugs, do the opposite: withdraw the plugcap, carefully avoiding a too wild movement of your hand that may result in a compromised connection cap - wire or even wire - coil. Then screw the little ferrule on top of the plug - a few turns is enough - and firmly press the Honda tool on it. No risk of damaging the porcelain and guaranteed no more prematurely falling sideways of the #2 and #3 plug, which would result in a hassle to get them out.
BTW, abstain from resistor sparkplugs, no matter what manuals may say.
Some further advice, if you'll allow me. Be very
terughoudend (reluctant) in 'repairs' and 'replacing' parts. Many have no idea how many kilometers these bikes
can and
will travel without you having to 'repair' things. Many
do have a drive 'to do things'. Don't start with just replacing parts and
if you do, do it step by step or you will never find out what was wrong. A proper diagnosis always comes first. We can guide you with that.
Expect some work cleaning the carbs. Ultrasonic is no guarantee. All can be done from the floatchamber side, so no sync afterwards is required. No need to separate them from the rack. Do
not 'conclude' carbs need a sync rightaway. The cause of a not so nice idle, lies usually elsewhere. Your engine can actually do tens of thousands of kilometers without needing a sync. Do
not 'assume' floats need readjusting. They never do, unless someone has messed with them. It is not even in the maintenance scheme. After being cleaned, this model carbs may require a socalled maintenance dose (say 15cc) of a fuel system cleaner at every tankfill. this has to do with the changed properties of gasoline. I'd opt for the designer fuels like Shell's V-power, BP's Ultimate and the like. You may want to verify the float chambers vent. To prolong the life of silencers, avoid short trips. This goes for your model even more, as they lack the little drain holes previous models had. Success!
