Topic: Thanks everyone

[CharlieVT]

I've done a few hundred miles on my 74 CB550 now that riding season has begun in Vermont. Thanks for all the help I have found on this board, both in the archives, FAQ, and from helpful replies to my queries.

The bike runs great, but I think it maybe a little lean. Header pipes are turning color quickly, making me think it is a little hot. The plugs look okay, virtually no deposits after a quick shut-down.
No real hesitation pulling at low rpms, and high rpm acceleration seems good too. But I think I'll change low speed jets to one size up just to see what happens. Some folks say if it runs okay don't worry about jetting, but I am concerned about burning valves/pistons. I do run it hard.

Question: It is safer to run a little on the rich side than a little on the lean side right?

BTW, I have figured out how to pull the float bowls without taking out the carbs. I use an air ratchet, with a socket that accepts one of those hex sided screwdriver tips, making a powered, right angle screwdriver. I can buzz those float bowl screws out pretty quickly, so changing out the jets is pretty quick.

http://home.earthlink.net/~cmiddleton01/bmwairheads/id7.html

[Bob Wessner]

Question: It is safer to run a little on the rich side than a little on the lean side right?

If you had to choose between the two (as apposed to neither), slightly rich would be better, less possible damage. Your comment about the pipes coloring quickly should be a warning sign, as you say, too lean, as well as your comment about no deposits on the plugs. What air filtration are you using, stock? What exhaust system, stock? Rather than changing out the low speed jets, have you adjusted the air/fuel screws to the optimum settings? Are you sure it is a low speed condition contributing to the lean condition? Have you done a plug chop to isolate plug condition at various throttle settings? Compare your plugs to these, might help diagnose things..

http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

[bill440cars]

                           Hey Bob, I'd been to that basic site and somehow I missed what you brought out.
          I appreciate that, even though I know that it wasn't for me. A person can't help but learn
          something, if he'll just keep his eyes open and check out what's given. Later on,  Bill

[bryanj]

If they are aftermarket pipes they will colour whatever you do so dont worry

[CharlieVT]

[ What air filtration are you using, stock? What exhaust system, stock? Rather than changing out the low speed jets, have you adjusted the air/fuel screws to the optimum settings? Are you sure it is a low speed condition contributing to the lean condition?
http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html

Good questions, thanks: Exhaust 4->1 from loud, fast n' ugly. Document that came with the pipes suggested opening up the jets a little. Prior owner had a 4->2 exhaust which I removed, I don't know if the bike had been rejetted from stock.
Airbox and filter are stock.
The plugs do look so free of deposits I do wonder if they won't look burned after more miles.
I don't have gauges for 4 carbs (bmw airhead guy, can't handle more than 2 at a time. 
I am going to ask local bike shop to do the balancing.  So, I should have that done first before screwing around with the jets, huh?
Thanks,

[oldbiker]

It is also worth checking your ignition timing as overheating can be caused by being a bit retarded.

[TwoTired]

At about 1/4 to 3/4 throttle settings, the slide needles dominate the mixture settings.  This where the throttle is set during most driving operations.

Almost certainly need to resynch carbs after that adjustment.  The main (WOT) and the slow jets can be changed with the carbs still on the bike, and no changes to Carb synch.

Cheers,

[dusterdude]

tt,at what throttle point would you say one would either richen the main jet or raise the needle a notch.

[TwoTired]

The main jet restricts the maximum fuel that can be delivered to the engine.  This occurs at WOT.  So, the main jet should be selected for size under that condition.  The needles futher restrict the fuel delivered from the main jet source at lower throttle settings.  Probably the fllowing chart is a good guide as to what to adjust for what throttle position.

Cheers,