Idle speed and timing advance
| Engine type | Idle speed | Ignition advance timing (before TDC) | |
|---|---|---|---|
| Leaded fuel | Unleaded fuel | ||
| 150A (XY6C) | 700 to 800 rpm | 8° at 850 rpm | |
| 150C (XY6D) | 800 to 850 rpm | 10° at 850 rpm | |
| K1G | 700 to 800 rpm | 6 to 10° at 750 rpm | 4° at 750 rpm |
| 171B (XU5S) 171C (XU5S) |
650 to 700 rpm (Solex) 700 rpm (Weber) |
10° at 900 rpm | 8° at 900 rpm |
| B2C (XU52C) | 700 to 900 rpm (manual) 700 to 800 rpm (automatic) |
??? | 10° at 850 rpm |
| B1A/A (XU5S) | 650 to 750 rpm | 10° at 900 rpm | |
| B1E (XU51C/W) | 850 to 950 rpm | 10° at 900 rpm | |
| BAY | 850 rpm | 10° at 900 rpm | |
| BDY (XU5M 3Z) | Controlled by EMS | ??? | |
| 159A (XU9S) | 650 to 750 rpm | 10° at 850 rpm | 8° at 850 rpm |
| D2A (XU92C) D2E (XU92C+) |
650 to 750 rpm (Solex) 750 to 850 rpm (Weber) |
10° at 850 rpm | 7° at 850 rpm |
| DFZ (XU92C1???) | 875 to 925 rpm | 10° at 850 rpm | |
| D2F (XU92C+) | 700 to 800 rpm | 7° | |
| D6A (XU9J2) | 800 to 850 rpm (manual) 850 to 950 rpm (automatic) |
5° at 850 rpm | 2° at 850 rpm |
| D6D (XU9J2) | 850 to 900 rpm | 2° | |
| D6C (XU9J4) | 850 rpm, not adjustable | not adjustable | |
| DKZ (XU9JAZ) | 850 to 950 rpm (Motronic) 850 rpm (UFIMA) |
??? | |
| DDZ (XU9M) | ??? | ??? | |
Some engines accept both unleaded and leaded fuel, others only one of them. The need for adjusting the advance timing arises from the fact that leaded fuel explodes at a slower pace. As a consequence, you have to set the ignition to an earlier time so that it will not be late for the piston passing over the top dead center position.