So I finally gave up searching for stock 7.5k ohm resistor spark plug caps and installed the NGK 5k ohm resistor caps on the bike, I was worried the shorter spark duration might negatively affect the engine but after a few hundred miles I haven't seen any signs to justify my worries. I did notice that the engine's idle was slightly smoother now that all 4 caps have the same resistance.
Im still on a quest to do the ton, but it seems no matter how well I have the bike tuned, 95mph is about all I can get out of it regardless of altitude. It's like there is some sort of invisible barrier right at 95mph. 
The bike pulls well all the way up to 85mph then it slowly builds momentum and stops at 95. I think there may be 3 possible reasons I cant hit 100 A. The speedometer may not be accurate at higher speeds after 42 years of use B. the persistent oil burning may be making a few horses lame and C. the cam chain being a bit stretched may be costing me a few extra ponies. It could be a combination of the 3, but as of right now I can only check one, so tomorrow Im going to do a high speed run with my GPS strapped to my leg and see how accurate the speedo is.
In the meantime Ive decided Im going to get a picture of the CB500 at every airport Ive flown into during my flight training, Ive been to a few already on the bike but I only just decided to start documenting each visit. A few are going to be pretty long trips, so Im going to need to hustle to get them all in before the snow starts falling. I rode the bike out to Fort Morgan airport (KFMM) this weekend, which is a small airport consisting of a single paved runway and is mostly used by crop dusters. Its roughly 60 miles from my apartment out to Fort Morgan and the bike did great running at 80mph the whole way out there and back.
Cool plan, and good start!
The drive chains get a little more efficient once they match themselves to the sprockets in use. This takes about 500 miles for any new chain on any sprockets, and a little more if the sprockets are brand new. The slack on the 500 should be around 3/4" with the bike on the ground (sidestand) because it tightens about 1/4" as the swingarm passes thru horizontal on the way to compressed shocks, where it gets looser again.
When you come by, we can talk about the Gentleman's Express thing: it takes 550 cylinders to reach the 61mm bore, so the cases also have to be bored out a bit: I have the parts of this engine arrayed on the floor, minus the cylinders, at the house. Next I have to pick out the pistons I want to use. Boy, wait 'till you see the carbs this guy just sent! I've never seen such beautiful 500/550 carbs before.
The top speed: you're into the realm of 'the little things' now that make the difference. Like:
Where are the vent hoses for the carbs located?
How do the fuel lines route, and what is the float bowl depth of the carbs?
What is the full advance (ignition) timing setting?
Which sparkplugs are you using, and what color are they during a long hard run?
Did you switch the air filter to a K&N pod-on-a-plate-in-the-airbox?
What tire pressures are you running?
These all matter above 7000 RPM and in top gear.
Once the engine is running to where it will redline, the fine tuning can begin. This then becomes a matter of broadening the powerband via external adjustments to the engine, like mixtures, timing, spark, air feed, and finally, exhaust. The latter has little to do with it, unless you can find a muffler that is longer than the rear fender, because otherwise the pipe is so short it has to time for the exhaust to complete expansion pulses well enough to be used as an extraction device. For examples, you can search for [old] photos of the CB500 racing, and pictures like my all-time favorite Mike Hailwood on the Honda Six, where you can get an idea of just how long the pipes have to be to work as suction systems (or, look under a car like a Shelby Mustang). On a CB750, this is just about even with the back of the rear tire, so on the 500 it is past the rear fender. As the pipes get shorter, the RPM they begin to work at gets higher: for comparison, the pipes you have now would have no effect until a little over 10,500 RPM, where they would just start to work. So, don't pin hopes on the pipes until you win the lottery?
