I'd say that unless the fuel mix is severely leaned out, then the engine should be ok.
If it was so lean that you had to worry about burning spark plugs or damaging the pistons or exhaust valves, the engine performance would be horrible.
When I first got my bike, the fuel map at mid-range (4800-6000 RPM) was so lean that you could feel the engine lose power, and if continued, would actually misfile at 5600 RPM.
After I had it remapped, so more fueling issues.
I'd have them check valve clearances, and check/replace all fluids (i.e. a full service).
I did that prior to having my bike dyno'd, since it would revving all the way to redline during the runs.
If it was so lean that you had to worry about burning spark plugs or damaging the pistons or exhaust valves, the engine performance would be horrible.
When I first got my bike, the fuel map at mid-range (4800-6000 RPM) was so lean that you could feel the engine lose power, and if continued, would actually misfile at 5600 RPM.
After I had it remapped, so more fueling issues.
I'd have them check valve clearances, and check/replace all fluids (i.e. a full service).
I did that prior to having my bike dyno'd, since it would revving all the way to redline during the runs.