Q: What type of engine oil to use for the YAMAHA YZ450F-2007?

For your YAMAHA YZ450F-2007, you should use a SAE 10W-30, 20W-40, 15W-40 or 10W-50 engine oil that meets the minimum API class SG and JASO MA standards . Yamaha recommends its Yamalube products: Yamalube 4 in 10W-30 or 20W-40 - recommended multi-purpose oils Yamalube 4-R in 10W-50 - alternative for warmer conditions Essential criterion: The engine of your YZ450F-2007 uses the same oil to lubricate both the engine AND the clutch. Never add chemical additives to the oil, as they can cause clutch slippage and damage your transmission. Special engine oils for wet clutches are already suited for this function. When filling: Completely drain the old oil, replace the oil filter, then slowly pour in the recommended amount (check your manual for the exact capacity). Always check the level with the oil dipstick after filling.

Question 1

What type of engine oil to use for the YAMAHA YZ450F-2007?

Accepted Answer

For your YAMAHA YZ450F-2007, you should use a SAE 10W-30, 20W-40, 15W-40 or 10W-50 engine oil that meets the minimum API class SG and JASO MA standards.

Yamaha recommends its Yamalube products:

Yamalube 4 in 10W-30 or 20W-40 - recommended multi-purpose oils
Yamalube 4-R in 10W-50 - alternative for warmer conditions

Essential criterion: The engine of your YZ450F-2007 uses the same oil to lubricate both the engine AND the clutch. Never add chemical additives to the oil, as they can cause clutch slippage and damage your transmission. Special engine oils for wet clutches are already suited for this function.

When filling: Completely drain the old oil, replace the oil filter, then slowly pour in the recommended amount (check your manual for the exact capacity). Always check the level with the oil dipstick after filling.

Question 2

Can I use an iridium spark plug on my YAMAHA YZ450F-2007 and what are the benefits?

Accepted Answer

The original spark plug for your YAMAHA YZ450F-2007 is a CR8E/NGK (standard resistance), as indicated in the technical manual.

An iridium spark plug is an improved version that uses an iridium electrode instead of standard nickel/platinum. The benefits are:

Better longevity (reduced wear, lifespan + 3 to 4 times longer)
More reliable ignition and slightly increased power at high RPM
Slightly optimized fuel consumption
Excellent for sports or competition use (your YZ450F is a motocross bike)

Compatibility: Yes, you can install a compatible iridium spark plug (same gap 0.7-0.8 mm and torque 13 Nm). Look for an iridium equivalent for CR8E like the NGK CR8EIX or similar, available at specialty stores.

Important: Ensure that the gap remains between 0.7 and 0.8 mm and tighten with a torque of 13 Nm to avoid any damage to the cylinder head.

Question 3

What are the cold and hot starting procedures for the YAMAHA YZ450F-2007?

Accepted Answer

Starting Procedures for the YAMAHA YZ450F-2007

The YAMAHA YZ450F-2007 is equipped with a liquid-cooled 4-stroke single-cylinder engine with a kick start and decompressor system. Here are the precise procedures to follow.

Cold Start

Set the fuel valve to ON
Put the gearbox in neutral
Pull the cold start lever (lever located on the engine) fully
Kick with a quick and vigorous motion
Important: Do not open the throttle while kicking - the lever may snap back violently
The KEIHIN FCR MX39 carburetor has a built-in accelerator pump, no acceleration is necessary

Hot Start (engine previously warmed up)

Push the cold start lever back to its original position
Run the engine at 3,000 to 5,000 RPM for 1 to 2 minutes to warm it up
Pull the hot start lever
Start the engine by vigorously kicking
Release the hot start lever immediately after starting

Checks Before Each Start

Check the coolant level
Check the fuel level
Check the engine oil level
Check the clutch operation

The normal idle speed of the YAMAHA YZ450F-2007 is 1,900 to 2,100 RPM. If the engine stalls regularly on hot starts, refer to the hot stalling FAQ for adjustment solutions.

Question 4

What is the torque for the spark plug for the YAMAHA YZ450F-2007?

Accepted Answer

For the YAMAHA YZ450F-2007, the torque for the spark plug is 13 Nm (1.3 m·kg or 9.4 ft·lb).

The recommended spark plug is a CR8E/NGK resistance type with a gap of 0.7 to 0.8 mm.

When tightening, use an appropriate spark plug wrench and adhere to the specified torque to avoid damaging the cylinder head threads. The spark plug gap should be checked regularly to ensure proper ignition and optimal combustion.

Question 5

What is the torque specification for the engine mount on the YAMAHA YZ450F-2007?

Accepted Answer

The torque specification for the engine mount varies depending on the attachment point:

Upper engine mount to frame (M10 x 1.25): 55 Nm (5.5 m·kg / 40 ft·lb)
Lower engine mount to frame (M8 x 1.25): 34 Nm (3.4 m·kg / 24 ft·lb)
Engine to front mount: 53 Nm (5.3 m·kg / 38 ft·lb)
Engine to upper mount: 55 Nm (5.5 m·kg / 40 ft·lb)
Engine to frame (lower): 53 Nm (5.3 m·kg / 38 ft·lb)

It is recommended to check these torque specifications after break-in or before each race to ensure optimal safety. Use a torque wrench to obtain the exact values.

Question 6

What is the spark plug gap for YAMAHA YZ450F-2007?

Accepted Answer

The spark plug gap for the YAMAHA YZ450F-2007 is 0.7 to 0.8 mm (0.028 to 0.031 inches).

This motorcycle uses an NGK spark plug type CR8E with an integrated resistor. The gap of 0.7 to 0.8 mm must be maintained to ensure proper ignition and optimal combustion of the fuel-air mixture.

You mentioned using a main jet #160 and a pilot jet #45 with a modified airbox and an Akrapovic exhaust. These modifications may affect the carburation, but the spark plug gap remains unchanged according to the specifications in the YZ450F-2007 manual.

If you experience ignition or starting issues after your modifications, check that the spark plug gap is indeed between 0.7 and 0.8 mm using an appropriate feeler gauge.

Question 7

How to adjust the accelerator pump of the YAMAHA YZ450F-2007 carburetor?

Accepted Answer

The accelerator pump of the KEIHIN FCR MX39 carburetor of your YAMAHA YZ450F-2007 is fully automatic and integrated. There is no manual adjustment for its operation at startup - it automatically provides the enriched mixture needed for cold or hot starting.

Operation and essential rules: The accelerator pump does not need adjustment for regular use, but you must absolutely not give throttle when starting the engine, otherwise you risk flooding the spark plug. Similarly, avoid 'revving' the engine (quick opening/closing of the throttle) after starting, as the pump's enrichment would make the mixture too rich and the engine would stall.

Cold engine starting: Turn the fuel tap to ON, put the engine in neutral, then fully pull the cold start lever to the stop. Then kick vigorously without touching the throttle. After starting, push the cold start lever back and run the engine at 3,000-5,000 RPM for 1 to 2 minutes.

Hot engine starting: Do not use the cold start lever. Pull the hot start lever (which injects air to dilute the mixture), kick, then immediately release the lever once the engine is running.

Inspection and maintenance: The accelerator pump contains a diaphragm, a spring, and a cover that can be inspected during carburetor maintenance. If the diaphragm has cracks or damage, it must be replaced. For fine adjustments of the pump flow (leak jet, throttle setting), consult an authorized YAMAHA dealer, as these interventions require specialized tools and technical expertise.

In case of starting problems: If you encounter difficulties, the problem usually comes from the carburetor adjustment itself (idle jet, needle, overall richness), not from the pump. First, check that the fuel level is correct and that the air filter is clean. If the engine stutters (pops on rapid acceleration), this may indicate a leak jet that needs to be checked. For any diagnosis or precise adjustment, consult an authorized dealer.

Question 8

What amount of engine oil is needed for the YAMAHA YZ450F-2007?

Accepted Answer

The amount of engine oil depends on the type of maintenance performed:

Simple oil change (without replacing the oil filter): 0.95 L (1.00 US qt)
Oil change with oil filter replacement: 1.0 L (1.06 US qt)
Total oil tank capacity: 1.2 L (1.27 US qt)

The recommended oils for this motorcycle are Yamalube 4 (SAE 10W-30 or 20W-40) or Yamalube 4-R (SAE 10W-50), or any oil of grade SAE 10W-30, 10W-40, 15W-40, 20W-40, 20W-50 that meets the API SG or JASO MA minimum standard.

Important: Never add chemical additives to the oil, as the engine uses the same oil to lubricate the clutch and the additives could cause slipping. Also, ensure that foreign particles do not enter the engine casing.

Question 9

Which jets to use for the carburetor of the YAMAHA YZ450F-2007?

Accepted Answer

The YAMAHA YZ450F-2007 is equipped with a KEIHIN FCR MX39 carburetor. Here are the exact specifications for the jets to use:

Main jet (M.J): No. 160
Main jet (M.A.J): Ø2.0
Idle jet (P.J): No. 45
Idle air jet (P.A.J): No. 100
Overflow orifice (P.O): Ø0.9

Needle and associated settings:

Needle (J.N): NFLR-4 positioned according to the clip
Notch (C.A): 1.5
Idle screw (P.S): 1-1/4 turns
Idle speed: 1,900 to 2,100 rpm
Float height: 8 mm

These specifications are from the technical manual of the YAMAHA YZ450F-2007. The main jet No. 160 is the standard reference for this model.

Question 10

Why won't my Yamaha WR450F-2007 start with the electric starter?

Accepted Answer

If the electric starter of your Yamaha WR450F-2007 is not working, the technical manual provides a step-by-step diagnostic. Start by checking that you meet the starting conditions: the gearbox must be in neutral OR the clutch must be pulled towards the handlebars. Both of these conditions activate the starting circuit cut-off system that protects the engine.

The first check concerns the main fuse. Access the fuse box and check the main fuse - if it is blown, replace it and check the wiring harness for any damage. Next, check the condition of the 12V battery: it must be sufficiently charged. If it is weak or discharged, recharge it or replace it. Then, check all connections of the quick connectors and cables between the battery, the starter, and the ignition switch - rust, dust, looseness, or short circuits must be repaired or replaced.

Next, check the ignition switch (main switch) by replacing it if faulty. If the starter still does not turn, check the operation of the starter motor itself by testing it directly with a jumper connecting the positive terminal of the battery to the starter wire - if the motor does not turn, it must be repaired or replaced.

Continue by checking the starter circuit cut-off relay and the starter relay with a 12V multimeter. If the starter responds but cannot be activated, check the neutral switch and the clutch switch - these safety switches must close properly according to your gearbox position and the clutch pull.

Other possible causes include a faulty diode in the circuit or a damaged starter switch. Important: never hold the start button for more than 10 seconds at a time to preserve the battery. If the starter makes a clicking sound without turning, the starter relay or the battery is likely at fault. If you hear no noise, first check the fuse and the connections.

The manual recommends removing the seat and the rear fender to access these components. If you do not have a 12V multimeter or specialized tools, most of these checks and repairs should be entrusted to a qualified mechanic, who can systematically test each component of the electric starting circuit.

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