Feeler gauge values

Feeler gauge, six blades. Click to fold it out and back in.

A feeler gauge is only as good as the target value you know. This table lists the measuring points on a two-wheeler and says honestly which values are documented and which are in the workshop manual for your vehicle. You will not find invented model values here.

Documented values from the ELDI manufacturer data (centring ring, feeler gauge 0.40). All other measuring points: target value strictly as per the workshop manual for the vehicle.

Measuring point	Target value	Tool	Source
Air gap, armature to pole shoe (Bosch ignition system)	at least 0.25 to 0.35 mm	Feeler gauge 0.40 mm for setting up, centring ring 79.8 mm	ELDI manufacturer data, centring ring
Setting up ignition and lighting coils (Hercules, Zündapp, Kreidler, Miele, DKW, KTM)	0.40 mm	Feeler gauge 0.40 mm	ELDI manufacturer data, feeler gauge
Contact breaker gap	as per the workshop manual (typically a few tenths)	Feeler gauge, 6 blades	Vehicle manufacturer
Spark plug electrode gap	as per the workshop manual or the plug manufacturer	Feeler gauge, 6 blades, bend the earth electrode only	Vehicle / plug manufacturer
Valve clearance inlet / exhaust (four-stroke)	as per the workshop manual, with the engine cold, at TDC on the compression stroke	Feeler gauge, 6 blades	Vehicle manufacturer
Piston ring end gap in the cylinder	as per the workshop manual	Feeler gauge, push the ring in square using the piston	Vehicle manufacturer
Rear sprocket / front sprocket alignment	no gap against the straight edge	Steel rule, feeler gauge to check the gap	Workshop practice

Gauge check

One gap, six blades, one feel for it. Set the blade thickness with the slider and check whether it goes through with slight resistance.

Feel for the measurement

The blade has to pass through the gap with slight, even resistance. If it slides through without resistance, the gap is bigger; if it jams, it is smaller. For sizes in between, combine two blades. Keep the blades dry: oil on the blade fakes a tighter measurement. The full guide is at using a feeler gauge properly.

The tools