Unfortunately, I have no way of knowing whether the timing change made any improvement in the temps because the thermometer only reads "Hi" over 230. So, it is possible that it was running much hotter with the timing advanced.
So, next steps are to richen up the idle mixture screws, replace the missing airbox drain hose, clip off the missing pinch hose, raise the floats to 12.5mm, and finally re-consider pods and rejetting.
Any other ideas?
You probably won't like these, either.
I switched to the Uni filters for much the same reasons you did. Cost. Uni cleaning is much cheaper over the years than the stock paper filter. However, I do feel it is less restrictive than the stock paper one, and should make lean burning carbs moreso.
One experiment that would cost you the price of a Honda filter, would be to install one. See, if your unknown temps seem cooler.
Even cheaper is the cost of some duct tape. I don't think I would apply the glue side to the foam. But, by partially doubling or folding it over on itself, you can narrow the filter area inlet of the uni filter. As a guess, block 3/4 to 1 inch along eachouter edge near the plastic support. Or, between the foam and screen on the inside of the filter. This will increase restriction, and deepen the pressure drop in the carb throats, drawing more fuel through the jets.
You could also temporarily plug the plenum drain hole to eliminate that as a potential leaning source. Then test for temp changes.
You could also try retarding the spark full advance by a say 5 degrees, to see if percieved temps are more acceptable to you.
Here's something maybe...
CB750 ignition timing (Shop manual pg 22) 6 degrees at 1000 RPM, 40 Degrees at 2500 RPM. (Presumeably K0 timing.) The K8 (pg 278) says Max advance is 35 degrees with the F mark at 10 degrees.
So, the 750 K0 has a 34 degree timing advance change and the 750 K8 has a 25 advance change.
The Cb550 K3 was designed for about a 25 Degree advance change.
I wonder what DYNA's advance range is?
I'm skepical that a 230 degree head temperature is a realistic goal. Particularly, when I know that combustion temps are in the 1300-1400 range, and the oil temps are supposed to be above 180. I try to visualize the temp of a cooling fin and it will certainly be hotter at the base of the fin than near the tip. A "looking" device will have a spot size. Is the spot looking at the fin or the cylinder wall area? Is yours seeing the IR radiation from the nearby exhaust headers? Just some thoughts.
Maybe later today I'll take my 550 down to South Bay Cycles. Tom's got an IR temp gun, I'm sure he'll let me borrow. I think it's got a laser on it, too.
About the drain hose. Have you seen the stock drain hose shape? It is a molded affair with one end belled significantly to fit over the plenum nipple.
Hmmm, nipples.....
