Topic: 75 CB550K Idle Issue

[MacGyver]

To start off I have been on here for a while and have just now gotten perplexed enough to ask a question.

The problem I am seeing is when the bike is cold I start it will full choke, throttle the choke down as the bike heats up until I get it off (usually happens the first mile of my morning commute).  On start I have to turn the Idle screw 3 full turns in to keep it Idling naturally.  After about 5 miles the bike starts to Idle at around 3k or 4k and I have to turn the Idle screw back out gradually until it full heats and I get it to idol at around 900rpm. This takes about 20 minutes of riding.

I took it to a guy back in March to have him sync my carbs since I don't have a vacuum gage and had him rebuild them while it was there just so I wouldn't have to struggle with getting them out and back in.  He used full rebuild kits from the Honda shop down the road and they are all synced great (at least I think since it Idols very smooth when it does).  The bike runs fine and pulls through the full RPM range.

I know I have to put new gaskets in it (I am waiting for the winter when I won't feel as bad about having it apart) since its leaking about 1 quart of oil a month, but other than that I don't have any other problems.

Any Ideas? Am I just expecting too much out of such an old bike?

[MacGyver]

Also I have a slight hesitation when rolling on the throttle from time to time at around 4k RPM like its bogging.

Could this mean im running a little too rich?  I don't see any blue smoke to indicate that so I'm at a loss.

[OldSchool_IsCool]

What do your plugs look like?

[TwoTired]

There is no fast idle cam on these carbs.  A cold engine doesn't atomize gas as well as a hot one, which is why you need choke, which also reduces engine efficiency.  Therefore, the throttle must be held open a bit to keep it running.

The main idle is set when the engine is a full operating temp.  It doesn't need a warm up before riding.  So suit up, start, and drive off with the choke on, and as you drive, take choke off incrementally.  While riding, your hand is on the throttle and you don't need the idle stop to hold RPM.  When the engine is warmed up again, you can take you hand off the throttle at stop lights and it will idle fine at the idle stop setting.

Earlier 500s and 550's had a friction adjust under the throttle so throttle could be added and held (if stationary running was essential to the owner).  It was removed to keep people from using it as a cruise control setting.  The high idle setting was then transferred to the rider.


Throttle hesitation may simply be an air screw adjustment.  But, if the induction and exhaust are no longer stock, there may be more adjustments needed.


Cheers,

[MacGyver]

That is what I was thinking considering I had picked the issue through my head about 500 times.  My bike does have the throttle lock, but I didn't know it was for aiding the idle.  I thought it was actually cruse control  .  Thanks for the info Two Tired, you really know your stuff.

As far as my plugs they look right.  Before I had it tuned they were a little white, but the new jets fixed that.