Motorcycle Repair: Valve adjustment, air plenum, leak down test

Question
2001 Intruder1500 LC, 4000 miles, purchased new. I have a noise that sort of sounds like a valve but isn't really tinny enough to be a valve. I have a seroius vibration in the engine at 4000rpm. I have gone from cover to cover in my maintenance manual and do not see a way to adjust the valves to help elliminate my suspicions about a loose valve. The bike accellerates great though I don't dare take it over 4 grand. I have checked plugs, air filter and fuel filter. I can not duplicate the noise in my shop with a no load situation. The noise resembles something loose vibrating like plastic, but I can not find any rub marks on anything around the air plenum. HELP!

Answer
Hi Dennis,

Hydraulic valve lash adjusters eliminate valve adjustment maintenance. Keep the engine oil and filter changed and level for best performance of adjusters. Although undesirable, it's normal to hear tapping or ticking. The noise may come and go.

The valves are not loose, but the valve clearance, when excessive, is termed as "loose." Excessive clearance causes noise; too little or no clearance causes damage. If you had a bent valve stem or cupped valve face/seat, you would know it. Perform a cylinder leak-down test to determine the condition of the engine/valves.

Respectfully,
Mark Shively