Well, according to the shop manual I have for the CBX, the valve clearance inspection interval was every 3750 miles. According to friends that have been M/C Techs for years, they held their clearance pretty well.
But, the CBX also came out 37 years ago. Valve clearance inspection intervals have increased dramatically since then. Even at the extended VCI intervals common today, the need to actually adjust the valve clearance is rare.
True, Valve check intervals have been greatly extended on most but not all bikes by any means in the metric market. Dealers and others will say things like you dont have to do the factory required 600 mile check, then after that, some might say, just check at 8,000 miles and your good to go for X amount of miles.
Thing is, your making a decision to ignore what the engine maker requires. If one is good with that, that is fine but there is a reason and the reason is, a few engines will be greatly out of spec and burn an exhaust valve, if the check isnt done, the maker can blame you for not doing it.
I personally dont think its a big deal but I stick to the manual and I am VERY relieved I no longer have to do valve checks.
I'm well aware of the manufacturers recommendations. I have several M/C Tech friends that work on bikes for a living, and I've built and/or worked on quite a few M/C engines myself. In most cases, the so-called Metric bikes will have a 16k inspection interval, Yamaha specs a 26k VCI interval on some of it's sportbikes.
Yes, I do recommend to those that ask, that they follow the manufacturers service schedule, and at least check the valve clearances.
The M/C engine I have the most experience with, is the GSX1300R. From experience with my own bike, to those engines I've worked on, to the experience of numerous friends that work on bikes for a living, or as a hobby, they rarely need any adjustment.
A buddy has 160k on his lightly-modded commuter/canyon-riding GSX1300R. He has checked the valve clearances every time it's recommended by the mileage. So far, they have never needed adjustment. Other than tires, brake pads, chains, sprockets, spark plugs, and air filters, (all normal consumables) the engine and trans and clutch are as it left the factory. Recently he checked the compression, and it's still on the high side of the spec. and even between cylinders.
My point is, metallurgy and manufacturer tolerances have improved dramatically since the 70's when the CBX was designed.
BTW, I've owned an FLHTCUI. So I'm not a Harley hater. I think they are fine for their intended purpose.
I just wanted to point out that no modern well-made streetbike has a valve inspection interval of 2k miles.
Your right. Honda is now recommending 8k for the CB1100. That's a big change from 1969. Most do not need adjusted. But you need to check.