Topic: CB550 normal operating temperature

[gmpb2]

Does anyone know what the normal operating temperature is on a CB550?  I have a vapor computer and I'm trying to find this info so that I can program it in.

[HondaMan]

On an 80-degree, 50% humidity day, sitting still after a 10-minute run, 20w50 oil:

The exhaust side of the head near the "flowers" is about 320 degrees F. The intake side is about 205 degrees F. The outer head fins are near 180 degrees F. The top of the #4 cylinder is about 170 degrees F and the lower fins are about 150 degrees F. The upper case is about 125 degrees. Simple, huh?

All values subject to change, lawyers notwithstanding. 

[HondaMan]

the fact that you know that just blows my mind 
so that being said, how hot is too hot at the base of the spark plugs (location of the sensor)?  specifically the #3 spark plug.

That fact that I know half of these things points out just how bizarre my life really is. 

Generally, the head chamber at the ring-style thermocouples we used in the '70s would show about 325 when knocking was starting (on #1 or #4 on the 750). This would indicate the need for more octane, usually. Higher octane burns slower, which moves the heat down into the cylinders a little more. Fuel supplies in the U.S. were a problem back then, so tourers would add a temperature gage setup to help them to know to slow down if all they were able to get was some substandard Regular gas or something. It's hard to hear knocking on these engines. The SOHC4 heads seem to actually LIKE more heat though, because the cylinder fins draw away sometimes too much heat (if you're looking for more power). The only thing to watch out for is the overheated exhaust valve. This is more of an issue on the undersquare 750 engine than on the 500/550.

[wdhewson]

My data were obtained during the snowmobile phase of life, but the distribution of engine temperatures was surprisingly highly dependent upon wind direction. 

Tail winds were plus 20 to 30F, headwinds were about minus 10F, and side winds could make the left or right cylinders give different plug readings.  Performed with thermocouple sparkplug gaskets.  It took a while to learn that.

Don

[Raef]

I logged back in to this site for the first time in almost a year looking for this info, I just put a 76 550 back on the road today after putting a hole in #2 piston last year

Hondaman for president

Mark

[steam-powered man]

some info from my temp gun, less than 3 minutes after a spirited 2hr ride today. 
'78cb550k engine with pods and oem 4/4, plugs are reading fine.  strong as hell to 8K, idles fine.  80 ambient:

topside of exhaust pipe, at the first elbow #1 136
                                                         #2 152
                                                         #3 137
                                                         #4 130

left, topside of engine case, just behind cyl base   209
right,                         "                                   211

topside of engine case, just behind starter   137

valve cover, top left   110
      "          top right   110     


am thinking of moving over to a synthetic, am a little concerned about engine case temps.  maybe i worry too much, but a "better" oil couldn't hurt(?)  this is a great thread.

[Duke McDukiedook]

Why are you running that high of an octane on your bike?
87 octane should be fine unless you are knocking or pinging.

[steam-powered man]

cheapo pods, OEM 4/4, under 2000ft elevation, NGK d8ea plugs, NGK 5ohm caps, point ignition, timing at "F", dwell at .016 +/-.

i didn't dick with carb tuning until after a full tune-up (adjust valves, new plugs, new points, new air filter, compression checked, new fuel filter, cleaned elec connections to provide adequate v at points, cct adjusted, etc).

then clean carbs, bench sync. 

my PD-46a carbs are as follows:

floats at 14.5mm
air screws at 2t
mains - 105
slows - 42
clip position - 4th down
needles - E2350F

plug chops show nice plug readings at 3000 and 4000rpm's, but #4 a little sooty at idle. 
idles nicely, pulls very strong to 8000rpm's and seems to want to go to redline.  i haven't dared to go there, as the bike is old.  cruising at 60 -70 is easy, with plenty of power to drive out of the corners in the short/twisty stuff.  had it up to 95 (indicated) in Addison/Cornwall over the weekend. 

am moving over to suspension tuning, fork oil changed last night and shopping for adjustable shocks.  mine are toast.   

good luck in your endeavors,
 

[HondaMan]

some info from my temp gun, less than 3 minutes after a spirited 2hr ride today. 
'78cb550k engine with pods and oem 4/4, plugs are reading fine.  strong as hell to 8K, idles fine.  80 ambient:

what size main jets are you using?  I haven't re-jetted yet for my pod filters (will be as soon as my jets get here),  so I know I'm running hot and lean.  The temps you just gave don't look bad at all (to me).  The highest temp I have registered so far is 315°F at the base of #3 spark plug.  that was during a stop and go 25 minute slow ride through the park not going more than 25 mph @ 80°F ambient.  That caught my attention real fast!  I'm hoping that after re-jetting it stays under 300°F. 

Hondaman, would an octane additive be a good or bad Idea? I'm running on 93 octane out of the pump (the highest you can get around here).

Generally, higher octane makes the engines run a little hotter. This is due to the slower-burning nature of higher octane, which pushes a little longer on the pistons during each power stroke before it "burns out". At high RPM there may not be enough time for all the fuel to burn, which then heats the head and exhaust side a little more when the fuel is still trying to burn during exit. The overlap on these engines is designed to have a very small amount of burning going on at that point, or else it will try to push back toward the carb and disrupt the next incoming charge. This reduces top end power with too much octane, which seems backward until you understand these short-throat, carbureted engines a little better. 

When testing for octane that's best, keep these things in mind: today's fuels burn slower because most have alcohol (ethanol) added to them. So, today's Regular fuel at 87 octane (at sea level) would have corresponded to almost 90 octane in 1974 when you examine the burn time. But, it burns cooler (also due to the alcohol) to reduce nitrous oxide emissions (sad, we all could use a little lift in traffic, don't you think?) in all engines. The knock resistance is a little better with alcohol because of this slower burn, too. But...if it is not ENOUGH octane, the bike will feel like it "hits a wall" at around 7000-7500 RPM on the 750, a little higher on the 500/550, so try Regular first, check it on the hiway, then try mid-grade, and so on.

On my 750, with slightly raised compression (9.2:1), I run Regular if I'm only putting around town or commuting on city streets. When I head to the mountains I use midgrade. If I head toward the lower plains, I go up in octane as my speeds rise: if I'm going to travel 80 MPH below 4000 feet, it's premium.

[scottly]

some info from my temp gun, less than 3 minutes after a spirited 2hr ride today. 
'78cb550k engine with pods and oem 4/4, plugs are reading fine.  strong as hell to 8K, idles fine.  80 ambient:

topside of exhaust pipe, at the first elbow #1 136
                                                         #2 152
                                                         #3 137
                                                         #4 130

I would be wondering why #2 is hotter than the others, shoe....