What does a valve shim do?

A valve shim, or valve spring shim or hat as it more commonly called, is a device used to set the height of installed valve springs in an internal combustion engine. This is also the name of a steel disk used to adjust the lash or tolerance of a valve on an overhead cam engine.

Are motorcycle valve shims universal?

Yes, all year YZ,WR 400,426, and 450’s use the same shims. The Yamaha part numbers are the same, so if you ask for 450 shims they’re going to be the same thing.

Are all motorcycle valve shims the same?

They are the same.

What happens if you don’t do a valve adjustment?

Too much or too little valve clearance can result in poor performance or a rough idle because the engine can’t “breathe” normally and operate at peak efficiency. If there’s too little valve clearance, the valves won’t fully close, causing excessive heat, and the engine will lose power.

Why do motorcycle valves need to be adjusted?

The reason valve adjustments are important is because the constant slamming of the valve causes it to recede ever-deeper into the head. First, the valve is unable to dissipate its heat into the head. Second, that small gap allows exhaust gases past the slightly open valve and seat at great speed.

How often do motorcycles need valve adjustment?

between 3,000 to 16,000 miles
How often should you adjust your valves? Your owner’s manual will tell you—bikes’ typical inspection intervals are between 3,000 to 16,000 miles (4,800 to 26,000 km). And some engines use hydraulic adjusters.

Will valves out of adjustment symptoms?

Too much or too little valve clearance can result in poor performance or a rough idle because the engine can’t “breathe” normally and operate at peak efficiency. Too much clearance means the valves will likely clatter and, over the long term, cause damage to the valves, camshaft lobes or rocker arms.