Topic: 1975 CB550K bogs at lower rpm

[Hillsdale Slim]

I have ridden this bike a fair amount this summer after lots of wrenching and lots of help from this forum. It is in "survivor" condition with 26k on the odometer. After it warms up, it bogs momentarily around 2k.  Since the engine likes to be revved, this is only irritating when riding around town on slow hilly corners, or making a turn after slowing down.  Here's what has been addressed already:
New battery, voltage reg, rectifier, coils, points. New cables.  Carbs rebuilt with new rubber, emulsion tubes, main jets, float valve, gaskets. Kept original pilot jets, jet needle, and air screws, all stock jet sizes. Bike has stock mufflers and airbox.  All intake boots sealed/not leaking. Valves have been adjusted and carbs synced. Timing and point gaps all good. The jet needles are set in the middle position. I have tried various positions of air scew settings, which affect the idle but don't seem to change the bog symtom much. Before I replaced the voltage regulator, it wouldn't charge the battery completely back up. Now it is usually between 12.6 and 12.8 volts after a 3 hr ride. I don't really expect anyone to know what is going on with my cb550, but outside input will spawn something that I hadn't though of, I'm sure!

[jeff d]

I am new to these machines, so you can demote this advice when the CB veterans weigh in!

I was able to eliminate a throttle bog/dead spot on my bike by doing a combination of two things:

- Setting the timing at 4000 RPM to the full advance mark using a timing light (strobe).  This made the static timing appear a little off, but it made a big difference in pep, and idle is still smooth.

- Adjusting the air screws methodically in very small increments.  I fine tuned down to 1/8 turn increments.  I didn't tune for idle, but for linear throttle response while riding.  If I am off by even half a turn there is a detrimental effect on throttle response.  The setting I ended up on is 2.5 turns out from lightly seated.

The engine feels really good from idle, and there is no stumbling or dead spot at any RPM.  The engine is a little more eager to rev above 4-5k than below, but maybe that is just the nature of the beast?  I wouldn't know as I've never ridden another SOHC.  But compared to other bikes, the throttle is very linear and predicable.