Head pipes can blue when getting too hot. It can be caused by a too lean condition (very high combustion temps), or a too rich condition (exhaust gasses pushed out while they are still burning).
It matters if the head pipes are single wall or two. Single wall chrome pipes are more prone to bluing than double wall.
All the 550's will tick on cool down. Moreso if there is a cool breeze on them. Even humidity matters. They don't have the spacers between the fins like the 750 does to damp the sound.
Visual signs that it is running too hot would be toasted valve guide seals.
Even the IR probes are problematic as the test spot size is about 5/8 inch. So you can't get in between the fins to see what the actual cylinder temp is. You just get some average between tip and root of the fins. It can be an indicator, though. Some data is usually better than no data, if you understand how to apply it.
You don't want white plugs, light tan is good.
But, that color is usually an average of all the throttle positions and the different engine loads the plugs "saw".
Let's say the main was too rich and the engine under loaded when it left deposits on the plugs. Then the mid throttle was too lean and fully loaded, burning of the deposits left by the main. You won't learn much useful by looking at plugs run under these conditions.
The 77-78 CB550K had more restrictive pipes than all prior models. This helped to retain some of charge (and heat) left by the previous fire cycle, to be "extra burned". This deprived the chamber of some fresh charge oxygen, and the carbs were set to provide less fuel for the available oxygen. This made the EPA happy enough to allow importation. However, change the exhaust restriction to allow more oxygen into the chamber, and the engine will run even leaner, as the carbs have know way of knowing there is more oxygen in the chamber.
The exhaust back pressure effects all throttle/slide positions in the mount of fuel needed for the engine.
I can say with confidence that if you just change the exhaust on a 77 or 78 CB550K to a more open type, your engine will run too lean and too hot. Another artifact of exhaust restriction is the heat retention. I think the 77-78 CB550K models were intened to run hotter. Again, that was current at the time thinking of the EPA as hot engines burn fuel more efficiently and produce less hydrocarbons in the exhaust. Unfortunately, engine internals weren't redesigned for extra heat tolerance Valve guides and seals are early casualties.
The original carbs were also set with the expectation that the stock air induction was present. Whereas, the falling piston creates the vacuum, it is equalized toward outside atmospheric at a rate that the stock induction regulates. Change the length or the filter membrane material or cross sectional filter area, and that equalization map is all different at the varying operation speeds and throttle settings.
Since jet flow volume is highly dependent on the throat vacuum levels, changing induction also changes the volume of what the carb jets deliver through any given orifice size. Further, there is no reason to expect the stock induction vacuum is in a linear relationship with the air speed or volume. There is even less reason to expect a replacement would behave in the same linear pattern as the stock induction, even if you measured a differential between old and new at some fixed point on the operational curve.
However, usually you can say that if a shortened induction path is applied from inlet to carb entrance, the vacuum levels will be lower and the fuel jets will supply less volume of fuel for any given air volume passing through the carb throat, making the engine run leaner.
Further, if the filter membrane has either greater area or in other ways provides a lower pressure differential across it, this ALSO reduces carb throat vacuum, and the resulting volume of fuel drawn from fuel jets.
The carbs only point of "information gathering" is at the exit point of the fuel jets. If you change engine needs beyond that point, or effect the information the carbs receive at that point, then the engine will not be supplied the fuel and oxygen in the ratio it needs to run properly. Almost all the mods I've observed in this forum, will force the carbs to create a lean mixture and a hotter engine than stock.
But, you asked if it was too high, right?
Perhaps the most useful way to know about engine heat is a CHT (Cylinder Head Temperature) gauge. For the air cooled Lycoming, a CHT of 375F is desirable (at 75% power), but in some high power low airflow conditions the temp regularly gets above 475F. 525F is considered harmful. It also has a thermostatic oil cooler to save the oil from destruction.
There are contact type CHT probes that use a ring lug fitted to the spark plug in place of, or under, the spark plug's gasket.
There are also thermocouple probes that can make contact between the fins nearest the combustion chamber.
The fin heat isn't going to be a useful measurement. Also, the there are oil temp senders that can be fitted where the drain plug is. However, this is a referred heat. And, is really only useful if you know what the heat is in normal situations. It can't tell you what the CHT is directly. Only if the oil is getting hot enough to become damaged.
There are temp labels that you can use to find out what yours is reaching. Such as:
http://www.palmerwahl.com/temp-plate-temperature-recording-labels.phpThe are also crayons and lacquers, that indicate temperatures, also:
http://www.omega.com/toc_asp/subsectionSC.asp?subsection=f&book=Temperature&all=1You could also shop around for a Fluke 80TK which you can use with a DMM to measure heat.
http://www.fluke.com/fluke/usen/Accessories/Temperature/80TK.htm?PID=55386Finally, what you'd really like to have while discovering proper jetting is an EGT (exhaust Gas Temperature) gauge.
This will tell if your engine is overtaxing the cooling fins. A good range is 1200-1600F.
http://www.tricktuners.com/egt_explained.htmFinally, even in perfectly tuned engines, the cylinder heat will be a function of the power output of the engine and the ambient air that is flowing over the cooling fins of the engine. But, I think a reasonable goal is to keep the peak below 450F and the average down below 300F.
Hope this helps,
