Hi folks, we had a nice spate of sunny 70s weather here in Tidewater Virginia recently and I got my bike out for a hop, and to do the biannual oil change.
My '88, some will recall, got an '01 engine change a while back, at 87K miles, and at the moment the total mileage is 114K miles.
The '01 engine had 1700 miles when I put it in, so it is up to around 29000 miles now. When I installed it, I checked the valve tappets, and for an experiment, I decided to just run this engine and leave it alone, except for oil changes twice a year (about 4500 mile intervals).
So far it starts instantly in all weathers, with the essential use of the choke according to the air temperature, and has run perfectly, cruising nicely at 70-75 mph much of the time when I take it out, and giving 70 mpg of 87 gas all the time.
I have this theory that if any of the valve tappets tightened up enough to hurt anything, it would show up with poor idling or running, and the clearance could then be corrected with no harm to anything. So far nothing, it idles perfectly at the correct 1300 rpm. Likewise, the spark plugs have not been touched from the factory, and the hot and cold starting are perfect, with no indication of misfiring under full load or any other time.
I have been using 5w-30 ordinary car oil in the engine, only, year around including the tropical summer heat we have here, and seen nothing adverse from it, nor any indication of low oil pressure such as the oil light coming on at idle.
Now this is just an experiment, on MY responsibility, and I recommend YOU run your equipment by the Owners Manual.
One or two here grumble about my 'dogmatic' pontifications, but my authority arises from my 50+ years of continuous motorcycling experience. I run my equipment on the basis of getting the maximum of good service for the minimum cost, and I assume there are plenty of practical riders out there who want the same thing. So if something works for me in that line, I offer it to you assuming that if you do what I do, you will get the results I get. But hey, we're all free to do what we please with our own equipment. That's Freedom.
Later note: Part of my experiment here is to verify for myself that 5w-30 non-synthetic car oil lubricates adequately to keep wear away in the top end, and so far it has, evidently. I don't plan to check the tappet clearances unless I get some symptom of distress or engine malfunction, but I will when the spark plugs eventually show evidence of large gaps which will cause hot-starting problems; and I have to take the tank off anyway to replace the plugs.