Service Manual

4-12
Table of Contents
Twin Cylinder Engine Service Manual
February 2017 - Digital Edition
CONTROL PLATE (THROTTLE AND CHOKE)
Troubleshooting
Engine Surging/Hunting
1. Start and run engine until at operating temperature.
2. Move throttle control to “fast speed” setting.
3. Check RPM with tachometer, top no-load RPM 3300 ± 100 RPM.
NOTE: See “Top No-Load RPM,” chapter 4, page 4-9.
4. If RPM varies beyond limits:
-Verify adequate clean air.
-Verify adequate clean fresh fuel supply.
-Verify not caused by parasitic load (transmission or clutch).
5. Troubleshoot to determine if engine related:
-Hold throttle shaft or link to maintain top no-load RPM.
-Refer to troubleshooting chart (in no particular order).
*Hold throttle shaft or link to maintain top no-load RPM
Symptom Possible Cause Action
If engine still
surges
Air leak into intake system between
carburetor and cylinder heads.
-Check and replace gaskets
-Check fuel pump and pulse hose
Lack of fuel in carburetor bowl. -Check fuel delivery system
-Check oat and needle
Fuel supply partially blocked in
carburetor
Air vents partially blocked in carburetor
-Check pilot jets, main jets and
nozzles, venturi ports
-Check air passages using
compressed air
If engine is
constant RPM
Linkage binding -Check linkage or governor spring are
not binding
Throttle shaft binding -Check throttle shaft and components
for debris/damage
Governor out of adjustments
-Adjust governor “zero”; see
“Governor Zero,” chapter 4, page
4-11
Governor Spring -Check spring is not binding
-Check spring length
If engine quits
running
Fuel supply blocked in carburetor
Air vents blocked in carburetor
-Check pilot jets, main jets and
nozzles, venturi ports
-Check air passages using
compressed air
-Check fuel solenoid function, see
“Solenoid,” chapter 3, page 3-34
6. Test run to operating temperature and verify top no-load RPM with tachometer.