How to Install Dirt Bike Valves – Before we dive into the installation process of valves, let’s run through what exactly valves are. Valves are devices that control fluid flow and pressure in systems like pneumatic and hydraulic systems, motors, and generators. In piping systems, valves are essential for managing the flow of liquids such as gases, vapors, and oil.
There are various valves, like globe, plug, butterfly, gate, diaphragm, control, pressure relief, and pinch valves, each with different models and functions. Manual valves are operated by pedals, hand knobs, levers, or wheels, and some have a geared system. They can be operated manually or through hydraulic or pneumatic systems, varying in size, and cost, and serving multiple ports with different functionalities.
By understanding what dirt bike valves are, you can better care for and install them when necessary. The same can be said about parts like grips and brake pads.
How to Install Dirt Bike Valves: Pre-installation
Before going into the installation process, there are some key parts to inspect:
Valve Guides
Valve guides are important for controlling the movement of engine valves, ensuring they move up and down precisely. This control is crucial to keep the valve face consistently in contact with the seat, promoting optimal engine performance and durability. Over time, valve guides can wear into an hourglass shape due to valvetrain forces, with slightly larger diameters at the top and bottom. This wear pattern increases the chance of broader contact between the valve face and seat, speeding up wear.
To address this, OEM service manuals specify service limits for the valve guide bore, and measurements are typically taken using tools like small hole gauges or micrometers. It’s essential to measure and qualify valve guides before installing new valves, following the specific engine’s service manual guidelines.
Valve Seats
Valve seats are essential for sealing the combustion chamber during the compression stroke, working alongside piston rings to ensure engine performance. As the engine runs, valve seats and faces wear together, potentially causing an increase in contact area and ovalization of the valve seat. Both types of wear can harm engine performance and longevity.
To address this, it’s recommended to recut valve seats before installing new valves. This guarantees a proper match between the valve face and seat, preventing accelerated wear of the new valve. For accurate re-cutting of valve seats and guides, it’s crucial to rely on a reputable shop specializing in cylinder head work with specialized seat cutting machines.
Valves and Springs
Valves and springs play a crucial role in the performance of an engine, and the choice of valve material influences subsequent considerations. One common modification involves replacing titanium valves with steel valves, trading a bit of performance for increased valve life. However, this swap requires attention to the valve springs. Steel valves are heavier than their titanium counterparts, disrupting the finely tuned valvetrains.
To compensate for the added mass, different valve springs are often necessary. Engine builders can turn to brands like ProX, which provide a range of valvetrain components, including valves, springs, valve stem seals, and shims, meeting or exceeding OEM quality. These components cater to various needs, offering direct OEM replacements and valve conversions that switch from OEM titanium valves to steel valves.
Keepers, Retainers, Seats, and Seals
When overhauling valves, it’s important to check the condition of valve spring seats and retainers for potential reuse. Examine these parts for wear, often caused by contact with the valve spring. If significant wear is detected, it’s advisable to replace them. Additionally, it’s a good practice to change keepers and valve stem seals during the overhaul.
After preparing new components, the final checks involve ensuring the new valve spring’s length complies with specifications and verifying proper contact between the valve face and seat. Measure the valve spring’s uncompressed length using the service manual as a reference. To assess the sealing interface, use a valve lapping tool with a transfer fluid like a Sharpie marker or machinist’s dye.
The resulting contact pattern and width are crucial; the valve face should display complete contact, and the width must align with the service manual’s specifications. Incorrect contact or width may suggest improperly cut valve seats or an attempt to install new valves into worn-out seats, highlighting the need for correct procedures to avoid damaging the coated or hardened layer on modern valves.
Installation Process
- Preparation: Before starting the installation, ensure that the new valves and components will create a well-sealing combustion chamber. Separate and pair the new components based on their location, considering variations in diameter and mass between intake and exhaust valves.
- Valve Spring Seats and Stem Seals: Begin by coating the valve spring seats with a light amount of engine oil or assembly lube and install them. Proceed to install the new valve stem seals, ensuring the correct seals are matched with the corresponding valve location.
- Valve Installation: Apply a few drops of oil just below the notch in the valve stem. Install the valves by gently rotating them past their respective seals, considering the differences in diameter for intake and exhaust valves.
- Valve Springs and Retainers: Lightly coat the valve springs and retainers with engine oil or assembly lube at their contact points, avoiding the area of the retainer where the keepers reside. Position the keepers inside the retainers, then place the springs and retainers in their respective locations on the cylinder head.
- Compression of Valve Springs: Use a valve spring compressor to compress the valve springs, allowing the keepers to drop into position. For stubborn keepers, a pick can be used to guide them into place.
- Final Compression and Tapping: Once the keepers are in their notches on the valve stem, remove the valve spring compressor. Repeat the process for the remaining valve assemblies. After compressing all valve springs, use a brass punch and hammer to tap the top of each valve stem a few times. This critical step ensures proper seating of all keepers before startup.
Post-Installation Checks
- Valve Clearances:
- Reassemble the rest of the cylinder head and engine.
- Check valve clearances and re-shim as needed, especially when new valves are installed.
- Cam Timing:
- Set cam timing according to the procedure in the service manual.
- Double or triple check the timing to prevent mis-timed engines, which can lead to catastrophic failures.
- Rotating Engine:
- Rotate the engine manually through several revolutions during reassembly.
- This practice helps ensure no mistakes have been made in the reassembly process.
- Leak Down Test:
- Qualify the seal integrity between the valve face and valve seat.
- Perform a leak down test before startup to assess cylinder leakage origin and severity quantifiable.
Valve Longevity
The lifespan of dirt bike valves is not determined by a specific number of hours, but rather by their ability to stay within specifications and form a proper seal against the valve seat in a 4-stroke engine. As a dirt bike owner and rider, understanding your bike’s performance and sound is crucial. To extend the longevity of valves, two major factors come into play: riding habits and bike maintenance.
Valves wear out due to heat and general wear, and while some preventive measures are straightforward, others may not be practical. Regular maintenance and mindful riding can significantly contribute to prolonging the life of your dirt bike’s valves.
Want to learn more? You can also learn how to replace a clutch or tighten spokes. You can also learn other things like cleaning a carburetor. Aside from these, you can also customize you bike by learning how to install dirt bike graphics.
