pdedse_imp said:
All this info is appreciated...one thing I would like to understand: what are some of the factors that make one bike need a valve check at 8k, another at 12k and even more?
Valve train design, screw/locknut need it a lot more often.
Air-cooling vs. liquid cooling, air-cooled engines need it more often.
Materials. Better materials such as cam surfacing and valve/valve seat materials can go a lot longer with less wear. Yamaha's Genesis design does not require a check until 26,600 miles. Most bikes seem to put the first check at 15,000 miles.
One thing to keep in mind also regard air-cooled engines especially are emissions regulations.
Valve timing is critical to a clean-running engine and as the valves wear, the engine may create more emissions than it should. Air-cooled engines are harder to design to meet current emissions standards which is one of the reasons they call for a very frequent check compared to liquid-cooled engines. This is something that is part of the specifications agreed upon between the OEM and EPA for emissions control compliance. It may well be that the CB1100 could reliably run 15,000 miles without any need for adjustment, with no risk of mechanical failure. But to ensure the engine is running cleanly, the interval is shorter, as being out of spec only 0.001" does make a measurable difference in tailpipe emissions.
One interesting requirement on this bike is that the cam chain tensioner be fully unloaded while checking valve clearance. Most bikes don't require this step and in fact it is the first bike I've owned that states this step in the service manual.
I called the service manager of my local Honda dealer, a guy who I trust and who is very knowledgeable about the deeper technological details of service and maintenance.
He said there are some bikes that Honda wants this step done for; it allows for a very precise adjustment of the valve train.
One thing I noticed right off when I first started the bike after finishing the check is that it was just as quiet as when it was new. Evidently, by completely unloading the tensioner and then letting it self-adjust, the cam chain was tightened a bit more. Also noticed the bike definitely seemed to run more crisply and strongly than before; that bit of slack might have retarded the cam timing just enough to take the "lively" nature out of the engine but it is certainly back now.
Adjusting the balancer also had a big effect on driveline lash, it really removed 80-90 percent of the lash and made throttle control much, much smoother during on-off transitions.
This is something to check for anyone feeling that driveline lash is excessive.
