Generac Power Systems XT-EFI Series User Manual

Section 5 Engine Diagnostic Tests
Diagnostic Repair Manual 31
Test 23 – Choke Test
Procedure
If generator is surging, it may be a carburetion problem.
A lean condition can cause erratic RPM. Slowly pull
choke out to see if surging stops. If it does stop,
carburetion should be checked.
Test 24 – Check Valve Adjustment
Adjusting Valve Clearance
Improperly adjusted valves can cause various engine
related problems including, but not limited to, hard
starting, rough running and lack of power.
Adjust valve clearance with engine at room temperature.
The piston should be at top dead center (TDC) of its
compression stroke (both valves closed).
Another method is to turn engine over and position intake
valve fully open (intake valve spring compressed) and
adjust exhaust valve clearance. Turn engine over and
position exhaust valve fully open (exhaust valve spring
compressed) and adjust intake valve clearance.
1. See Figure 5-13. Loosen rocker arm jam nut. Turn
pivot ball stud while checking clearance between
rocker arm and valve stem with a feeler gauge.
Figure 5-13. Adjusting Valve Clearance
2. See Figure 5-14. When clearance is correct, hold
pivot ball stud with Allen wrench and tighten rocker
arm jam nut to specified torque with a crow foot
wrench. After tightening jam nut, recheck valve
clearance to make sure it did not change.
Figure 5-14. Tightening Jam Nut
Adjust Valve Clearance (426cc Engine)
See Figure 5-15. Check and adjust the valve to rocker
arm clearance as follows:
1. Remove the four screws attaching the valve cover
and remove valve cover.
2. Discard valve cover gasket.
3. Loosen the rocker jam nut (A) using a 10 mm
wrench.
4. Turn the pivot ball stud (B) using a 14 mm wrench
while checking clearance between the rocker arm
(C
) an
d the valve stem (D) with a feeler gauge.
Adjust clearance per Table 5-2.
Install Rocker Arm Cover
1. Use a new rocker arm cover gasket. Install rocker
arm cover and retain with four screws.
Results
Adjust valves to specification and test. If problem
continues, refer to flow chart.
.
Figure 5-15. Valve Clearance Adjustment (426cc)
Table 5-1.
Rocker Arm Jam Nut ft-lbs
208/389/42
0 9
to 12
2
20 6
42
6 10
410/426/53
0 1
4.5
000258
Table 5-2.
Engine Intake Valve Exhaust Valve
208 0.004 inch 0.006 inch
220 0.001 - 0.002 inch 0.0018 - 0.003 inch
389/420
0.006 ± 0.0008 inch 0.008 ± 0.0008 inch
410/426/
530
0.002 - 0.004 inch 0.002 - 0.004 inch
A
B
C
D
001812

Generac Power Systems XT-EFI Series Specifications

General

Brand	Generac Power Systems
Model	XT-EFI Series
Category	Portable Generator
Language	English