F510 & F525 – ENGINE STARTS HARD OR STOPS WHEN HOT

Conditions:
• Transmission in neutral
• Park brake engaged
• PTO disengaged
• Engine hot

27. August 2021 by samuel07042012
Categories: F510-F525 | Leave a comment

F510 & F525 – LACK OF FUEL IN CARBURETOR

Conditions:
• Transmission in neutral
• Park brake engaged
• PTO disengaged

27. August 2021 by samuel07042012
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F510 & F525 – ENGINE FLOODING

Conditions:
• Transmission in neutral
• Park brake engaged
• PTO disengaged

26. August 2021 by samuel07042012
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F510 & F525 – ENGINE CRANKS BUT WILLNOT START

Conditions:
• Transmission in neutral
• Park brake engaged
• PTO disengaged
• Key switch in “START” position

26. August 2021 by samuel07042012
Categories: F510-F525 | Leave a comment

F510 & F525 – AUTOMATIC COMPRESSION RELEASE

Function:
To lower engine compression for easier starting.

Major Components:
• Fly-Weights
• Spring
• Tab

Theory of Operation:

The automatic compression release uses fly-weights and a tab to slightly lift the exhaust valve which releases engine compression. The compression release assembly is attached to the camshaft and cannot be serviced separately.

With the engine cranking, the fly-weights (A) are held inward by spring (C) tension. A tab (G) that is connected to one of the fly-weights moves up (away from camshaft) as the fly-weights pivot inward. In this position the tab is held above the camshaft heel (E).

During the compression stroke, with the engine cranking, the tab contacts the exhaust valve lifter (F) and holds it off the camshaft heel a small amount until just before TDC. This opens the exhaust valve slightly just after the intake valve closes to release some compression for easier starting. A stop pin (B) locks the fly-weight and tab in the upper position to prevent the tab from being pushed down by the exhaust valve lifter.

When the engine starts and the engine speed is about 600-900 rpm, centrifugal force moves fly-weight (I) outward unlocking the fly-weight and tab from the stop pin. Now the fly-weights (H and I) overcome the force of the spring and pivot outward until they contact stop pin (B). The release tab moves down (toward camshaft) below the camshaft heel until it no longer holds up the exhaust valve lifter and the engine runs with full compression.

26. August 2021 by samuel07042012
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F510 & F525 – COOLING SYSTEM

Function:
Remove heat from engine.

Major Components:
• Intake Screen
• Flywheel Fan
• Engine Covers
• Cooling Fins

Theory of Operation:

The engine is air cooled with air flow provided by a fan (A) that is a part of the flywheel. During operation, the fan draws air in through the intake screen (B). The intake screen rotates and cuts debris into small pieces to help prevent the cooling fins from plugging. The blower housing (C) and cylinder block covers (F) then direct the air flow past the cooling fins (D) of the cylinder block and head. Most of the cooling air flows through passages in the cylinder head (E) directly over the valve area. This increased cooling capacity in the valve area helps to minimize valve sticking and seat wear from overheating. The cooling fins are cast into the engine block and
cylinder head to increase their surface area to allow
more of the heat generated by the engine to be
transferred to the cooling air.

On F510 (S.N. 100204— ) and F525 (S.N. 100393— ), a hole and duct in the blower housing direct cooling air flow over the fuel pump. The engine shroud or crankcase has several holes added to it directly in front of the air cleaner to allow cooling air flow over the carburetor. The cooling air flow decreases fuel temperature in the fuel pump and carburetor to help prevent vapor lock.

It is important that the intake screen remains free from debris for proper air flow. The engine covers should not be removed or altered, as cooling capacity will be reduced. Cylinder block and head cooling fins must remain clean to properly dissipate heat. Debris build-up on the intake screen or fins will affect the volume of air setting to the carburetor.

26. August 2021 by samuel07042012
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F510 & F525 – BREATHER SYSTEM OPERATION

Function:
Maintain a vacuum in the crankcase to prevent oil leaks.

Major Components:
• Breather Valve
• Maze
• Breather Passage
• Oil Return Passage

Theory of Operation:
The engine is equipped with a breather system that allows air to escape easily from the engine, but restricts air coming in. As the piston moves downward during power and intake strokes the volume of the crankcase (H) decreases. To prevent a buildup of pressure, oil-laden air flows through the breather passage (F) and breather valve (D) into the space under the rocker arm cover (E). In order to prevent excess oil loss, the air is routed through a maze (C) in the rocker arm cover where the oil separates out. The non-oily air then passes through breather hose (B) and into the air cleaner housing (A) between the air filter and the carburetor. The separated oil lubricates the valve train and returns to the crankcase through the oil return passage (G). When the piston moves upward during compression and exhaust strokes, the volume of the crankcase increases. Crankcase vacuum increases and closes the breather valve preventing air flow into the crankcase. A restriction (I) and oil in the oil return passage also help to limit air flow into the crankcase. The result is that a small vacuum is maintained in the crankcase.

26. August 2021 by samuel07042012
Categories: F510-F525 | Leave a comment

F510 & F525 – ENGINE LUBRICATION CIRCUIT

A—Engine Lubrication Circuit
B—High Pressure Oil
C—Return/Pressure-Free Oil
D—Oil Filter
E—Engine Oil Pressure Relief
F—Engine
G—Oil Pump
H—Oil Pump Screen
I—Sump
J—Transaxle

The F510 (PA420A) and F525 (PA540A) engines utilize a common sump (I) supplying oil for engine and hydrostatic transaxle needs. The sump is an integral part of the transaxle casting. (See Lubrication System Operation in this section for further information.)

26. August 2021 by samuel07042012
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F510 & F525 – LUBRICATION SYSTEM OPERATION

A—Oil Pressure Relief Valve
B—Relief Valve Spring
C—Oil Pump
D—Screen
E—Oil Pump Gear
F—Lower Balancer Link
G—Balancer
H—Oil Return Passage
I—Breather Passage
J—Upper Balancer Link
K—Crankshaft Ball Bearing
L—Connecting Rod Journal
M—Connecting Rod Passage
N—Camshaft Bearing
O—Crankshaft Main Bearing
P—Oil Pressure Switch
Q—Oil Filter
R—Pressure Oil
S—Pressure-Free Oil
T—Oil/Air Mixture

Function:
Lubricate internal engine parts.

Major Components:
• Screen
• Oil pump
• Oil pressure relief valve
• Low oil pressure switch
• Oil filter with bypass
• Internal oil passages

Theory of Operation:

A positive displacement gerotor pump is used to pressurize the lubrication system. The oil pump is driven directly off the crankshaft gear. The lubrication system is protected by an oil pressure relief valve, low oil pressure switch, and an oil filter with bypass.

The oil pump (C) draws pressure free oil (S) from the sump through screen (D). Pressure oil (R) from the pump flows through the pump outlet passage past the oil pressure relief valve (A). The oil pressure relief valve limits the oil pressure to approximately 296 kPa (43 psi) and protects the oil pump from damage if an oil passage becomes blocked. If oil pressure exceeds 296 kPa (43 psi), the relief valve opens allowing oil to return to sump. Relief valve is not adjustable.

Pressure oil from the pump outlet passage flows to the oil filter (Q). The filter contains a bypass valve which opens if the element becomes plugged to insure engine lubrication. An oil pressure switch (P) mounted in the oil filter manifold turns on a warning light if oil pressure is below 28 kPa (4 psi). Filtered pressure oil flows through a passage in the oil sump to the crankshaft main bearing (PTO side) (O) and then to the camshaft bearing (N). Drilled passages in the crankshaft distribute oil from the main bearing to the lower balancer link (F), connecting rod journal (L), upper balancer link (J), and crankshaft ball bearing (flywheel side) (K). A drilled passage (M) in the connecting rod allows oil from the connecting rod journal to lubricate the piston and cylinder. Pressure-free oil flowing out of the crankshaft ball bearing or upper balancer link also lubricates the balancer (G). A drilled passage in the top of the balancer allows oil to flow to the support shaft and balancer bushing.

The rocker arms, valves, and pushrods are lubricated by an oil/air mixture (T) and carried to the rocker arm cover through the breather passage (I). The breather passage is located directly above the upper pushrod. The oil from the oil/air mixture is separated from the air through the breather maze and flows to the bottom of the cylinder head. This oil drains back to sump through an oil return passage (H) located in the bottom of the cylinder block directly under the lower pushrod.

26. August 2021 by samuel07042012
Categories: F510-F525 | Leave a comment

F510 & F525 – INTERNAL ENGINE COMPONENTS

A—Flywheel
B—Cylinder Head
C—Breather Valve
D—Intake Valve
E—Rocker Arm Assemblies
F—Exhaust Valve
G—Push Rods
H—Piston and Connecting Rod Assembly
I—Cam Lifters
J—Twin Gears
K—Camshaft
L—Automatic Compression Release Mechanism
M—Oil Pump Assembly
N—Crankshaft Assembly
O—Balancer Assembly

26. August 2021 by samuel07042012
Categories: F510-F525 | Leave a comment

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