Topic: 1978 Honda CB550K idle

[beelsamin]

I've been returning this 3 P.O. 550 from the grave and am nearing the point where it may be on the road soon. I've seen references in a couple of posts where people have indicated it won't run well or at all without the air box and filter installed.I've cleaned the carbs,installed new points,condenser,plugs,fresh fuel in a clean tank and although I haven't set the tappets(waiting for my gauge on order). She will not idle anywhere near 1000 RPM,she will idle quite happily around 3000 RPM but adjusting the idle screw kills her.
So, am I having this problem because the air box is not installed, or should I just dive back into the carbs?
Thanks

[beelsamin]

Well digging around in some other posts I made some more adjustments,turned the idle mix screws out only one turn,went over the float heights again,made sure all the clamps were snug and re-adjusted the throttle cables,she will idle around 2000 RPM now but still surges a bit up to 3000 RPM,if I turn the idle adjuster down she will die,still not sure why it wont get down to the 1000 RPM idle point but I can see some light at the end of the tunnel.I'm hoping adjusting the tappets when my tappet gauge gets here will make another improvement.

[beelsamin]

Duh me,just found out the 1978 CB550K float setting is 12.5mm not 14.5mm and I just wrestled them back on after checking that I had them at 14.5 I'm getting to know this bike..intimately....my wife is getting suspicious

[Jonesy]

Don't forget the fast idle cam... if the choke is pulled out at all it will prop the throttle open.

[dnewman417]

I'm running a CB550K engine without the air box, but I put in 105 main jets, the IMS is 1 1/4 turns ... runs great.  Now I'm adding a MAC 4 into 1 exhaust , so more carb twiddle will be in order.

[Old Crow]

Hi:
I have the same bike, same year. It has served me really well for six years of commuting and just plain fun. I tried cone air filters a month ago and it's been down hill from there.
During the attempts to make the cones work i did the carb routine, adjustments to whatever bits I could, cleaning, with no results. No power, no acceleration, but rideable with the choke part way out.
I put the stock air box back and bingo..I have my old bike back. It was fine for two 60K (40 Mile) trips. Then just as you describe it, won't back down from any loads while riding, neutral idle is about 3000.

I rechecked the air screws again(the ones on the engine side of the carbs tucked in a recess of the float bowls) That worked for a while and now the weird idle is back.
Besides that I have oil spouting out of the cylinder to OHC gasket! WTF? At least I think that's were it's from. I haven't had time to look.
there's no exhaust smoke, it's got lots of power, rocket acceleration.
Let me know how your making out.

[Old Crow]

I assume those 105's are not stock. How did you pick that number and where did you get them?
Are you running cone filters?

[ryder60]

I'm running 110s, a 4 into1 and using the rubbers off the airbox for velocity stacks.  The rods are as high as they can go and the air is out 1-1/4 turn.  It idles and runs very well up to 7000RPM and then goes lean.  I'm putting in 120s.

[apoji187]

I have a 78 550k with pods and drag pipes that i just finished tuning, figured I'd share my settings in hopes they'd help you out.

With some searching and extrapolating from this site, and after taking the carbs off about 5 times, I can offer this:

Float height 12.5 (I blew air into the rack with my mouth via a tube to the fuel inlet and listened to their shut off points)
Idle screws 2.5 out
Clean idle jets (use strand from copper wire if you have to).
Approx. 111 main jet. (I drilled mine in increments from the stock #90 as I tuned)
Needle raised to #4 position (really helped with mid range "searching")
New properly gapped plugs.
Make sure your choke arm clears the pods
Good charge on the battery.

I will say this, float level and the clean idle jets had more to do with the stability and driveability of the bike more than anything. It just feels so much better. The bike starts with barely any choke, and you can turn the choke off completely after a few seconds.

I ended up adjusting floats *last* and its perfect now. I should have adjusted them *first*

Of course, your bike will be different - your needle position or main # might be different than mine due to the pipes, etc.

[beelsamin]

I'll be running her with the stock airbox,I'm just waiting on some parts to complete the box,and I'll be setting the floats to the 12.5mm height.I'm still a little concerned about the idle screws,Honda says 1.5 turns out and people here have said anywhere from 1 to 2.5 turns,guess I'll factory set them and then adjust from there.

[ryder60]

1 1/2 turns out is fine.  If the screws are on the airbox side of the carb they monitor air.  Turning them in enrichens the idle and turning them out leans the idle.  Vice-versa if the screws are in the engine side of the darb.  Then they meter fuel and turning in leans and turning out enrichens.
When my engine is hot and I'm going from closed to open throttle quickly it will want to stumble coming off of low RPM.  Enrichening the idle by 1/4-1/2 turn helps it over the flat spot.  That's also why the needles at raised to their max.
I think you are on the right course.

[beelsamin]

Well I've got the floats at the factory setting of 12.5 and she did finally idle at around 1200,the idle screws set at factory spec. out 1.5 turns,I'll post again as soon as I get the airbox on her,I've been told she really won't settle down until the airbox and filter are in place.