Topic: No longer a carb virgin

[needswork]

Well Ok. I didn't do a complete rebuild, but I did get into them 

Well, as some of you know, I bought the bike ('78 CB550K w/ 4 into 1 and cone filters) last summer and although it ran, it needed a fair bit of work to make roadworthy. I did some work myself and took it to a mechanic for some of the work. The mech' had it for a long time and finally I said "Hey, the season is just about done, is it rideable or not?". His answer was "yes but it's not 100%, still more carb work needed". I took it and drove anyway, it ran pretty good but would "break up" at around 5000-6000 rpm. The mech' installed 118 mains and said I need larger - probably 125.
Last weekend I removed the mains and ordered 125 from the local Honda dealer, I picked them up yesterday ($2 a piece) and installed them.
Now, the engine is still a bit of a #$%* to get warmed up without driving (still too much ice and snow here) and pops and sputters but once warmed up she's pretty smooth and revs freely. I didn't rev it past 6000 as the fumes and heat in the shed were a bit much and I didn't want to break something else. But I think this is going to make a big difference, I can't wait to take her out!
The carbs are surprisingly easy to take out (as are the main jets), the pilot jets are a #$%* (never did get them out). The carbs are fairly easy to re-install. My choke set-up is still needs tweaking.

[Bob Wessner]

Good to hear you are making progress, congratulations. If you plan to do any extensive engine running while the bike is stationary, I would strongly suggest a fan to blow air across the cylinders.

[Bodain]

See how much fun it is when you jump in and do it. <GRIN>

I did the carb battle myself on my 550. I drilled my mains. I'm thrifty.. The results were excellent.
I think all old CBs are cantankerous in the cold. Well as cold as it gets in Texas. If it's below 50 degrees my 550 will sit and pfff pfff pfff from the number cylinder until it warms up, then it will stop and run fine. About 3 months ago I make it my mission to find what was causing this. I never did.

[needswork]

Thanks guys.
Bob, It's still cold in the shed but yeah I think about temperature ever since that time (I was drunk) and I started her up. After 5 or 10 minutes the headers were orange- yeah- not red, ORANGE!

Bodain, that pfff, pfff is from which cylinder? 1? Mine is from 1 and 4., especially 1. "I think all old CBs are cantankerous in the cold"- I think you're on to something there, that seems to be a concensous here from the posts I 've read.  I think I'll live with it for the couple of blocks the bike #$%*es until it's up to temp. She's got character 

[Bodain]

Mine is on Cylinder number 2. I spent and entire weekend on this problem alone. Since I don't know what's causing it. My thought was make some changes and try to make the problem move to a different cylinder.

I swapped Plugs. No change.
I swapped Plug wires. No Change
I swapped Coils. No change
I swapped Points and Condensers. No change
I intentionally adjusted float height high and low on that carb. No change.
Time is dead on.
I adjusted valves too tight. Too loose. No change.
New Piston and rings.. Compression is excellent.

Like I said. I was on a mission. I was determined to find the cause. I havn't found it. I could never get the problem to move.

My best guess is a sticky valve when the engine is cold. As the engine warms it stops. Still I'm not certain.

Cold is relative.

If the bike sits all night and I start it in the morning at say 60 degrees. I never get the pff pff..

On the other hand. If I start it cold at say 45 degrees. Then I get the pfff pfff from cylinder number 2 until it the engine warms.

[TwoTired]

The CB550 in stock configuration was NOT cold blooded until the 77 and 78 K models with the leaner burning carbs.  They were still immediately driveable with a proper choke setup, though.  At least, my 78 stocker was.

Colder spark plugs (D8EA) will make them all cold blooded, as can intake and exhaust changes from stock that lean the idle and mid mixtures more than what the stock bike had.

The Cb750, Cb400 normally use the D8EA.  That's why the concensus about them all being cold blooded.  Ask Gordon why he runs his Cb750 with D7EAs in winter, now.

Bodain,
Did you ever synchronize the carbs?  And, were all the cylinders exactly equal in compression numbers?  Since you suspect a sticking valve when cold, do a compression test with a cold engine.  Lastly, did you eliminate a leaky intake runner on Number 2?

Cheers,