What would cause my engine to rattle when idling but not at high speeds?

What would cause my engine to rattle when idling but not at high speeds?
Tappets (lifters) require adjustment. Even hydraulic ones need a flush periodically, especially when inferior oils/ a mix of mineral and synthetic/long periods between oil changes or the engine not been used for long period.Timing Chain stretch (early large engines, commercial engines, small lower end car engines, motorcycles).Timing belt/auxiliary (alternator/serpentine/power steering belt) idler or adjuster bearings are becoming quite common.Primary drive (motorcycle engine derived vehicles), clutch basket (Ducati motorcycle).Inertia (throwout) clutch (twist and go, variomatic etc).Clutch cover/clutch release bearing.Engine mounting, exhaust bracket failure.




The easiest ways to find the general source of rattles is either by observation or get a long screwdriver or thin stick, put one end to different parts of the engine and press the other just in front of your ear where the jawbone hinges. BEWARE OF MOVING/ROTATING PARTS. Where the noise is loudest and in time with the rattle in the other ear is the area that needs your attention.