Two-stroke outboard motors of the Japanese brand Tohatsu The 5 horsepower model is perhaps the most popular choice among inflatable boat owners and small keel boats. However, even the most reliable equipment requires regular maintenance, and the carburetor is the core of the fuel system, and it depends on the stability of the start, the speed of the engine at low speeds and the absence of failures when the throttle is sharply opened.
Owners often face situations where the motor is unstable, idling or fuel is being used unreasonably fast. Most of the time, the problem is contaminated channels, wear of the stop valve needle or factory adjustments to the mixture. Understanding the working principles and design Tohatsu 5 carburetor will allow you to independently diagnose the malfunction and return the outboard motor to the factory traction without expensive treatment to the service.
Consider in detail Construction of the fuel supply system, algorithms for correct adjustment and typical errors that are allowed during maintenance.
Design features of the fuel system Tohatsu 5 hp
Carburetor installed on five-strong engines TohatsuThis means that the fuel is not flowing by gravity, but is forced by pressure differences in the engine crankcase, which allows the engine to operate steadily even when the boat is rolling or moving along a steep wave, when the fuel level in the float chamber can change.
The main elements of the unit are the housing, which is mounted diffuser, throttle and jelly system. float-chamberIt's a floater that runs through the lever and acts on the shut-off valve needle, and when the float chamber is overflowing, it pops up and shuts off the fuel supply, preventing it from spilling into the intake manifold.
The air-fuel dosing system is governed by two main mix quality screws: one, often labeled with the letter "H", is responsible for operating at high revs, adjusting the flow of the mixture through the main jigsaw. The second screw, the "L", regulates the mixture at low revs and idling. Incorrectly configuring these elements, the engine either "choked" or overheated due to too poor a mixture.
Symptoms of malfunctions and diagnosis of carburetor
Before disassembling and cleaning, you need to clearly identify the nature of the malfunction. Symptoms can indicate both problems with the carburetor and related systems, such as an air suction or a clogged fuel filter. Competent diagnosis saves time and does not change the serviceable parts.
Owners often confuse three engines with ignition problems, but if the engine smokes, has black soak on the candle and does not keep idle speeds, then with a probability of 90% to blame fuel-mixGasoline oversupply (rich mixture) washes away the oil film from the piston, which is critical for two-stroke engines.
⚠️ Attention: If after a long parking the engine starts and immediately stops, do not immediately try to adjust the screws quality. 80% of the time the reason lies in the evaporation of light fractions of gasoline and the formation of resinous plaque in the jikler.
For accurate diagnosis, use the following list of signs:
- 🔥 The engine is not idling: The engine stalls immediately after the gas discharge, a constant gassing with a gas handle is required.
- 💨 Acceleration failures: When the throttle is sharply opened, the engine "chokes", jerks appear before gaining momentum.
- 🌫️ Black smoke from the exhaust: indicates a re-enriched mixture, the candle is covered with a black oily coating, power drops.
- 📉 Maximum power drop: The boat does not go on sleeve, the engine "does not pull" under load, it is possible to overheat with a piston.
Also worth paying attention to the state of candlelight. Unscrew the spark plug after running the engine under load. The brick-brown or light brown color of the insulator indicates the proper operation of the carburetor. Black, velvety nagar indicates a rich mixture, and white, with melted electrodes, indicates the dangerous poverty of the mixture.
Tools and preparation for maintenance
Working with a carburetor requires cleanliness and a specialized tool, and using inappropriate items for cleaning jellyclera, such as needles or wire, is strictly prohibited, as it can change the geometry of calibration holes and disrupt patency.
For quality service, you will need a set of screwdrivers (including cross and flat small size), tweezers, a rag that leaves no pile, and a special carburetor cleaner in an aerosol. It is also recommended to have a remix on hand that includes new gaskets, membranes and a valve needle, since old rubber products lose their tightness after removal.
Use only carburetor cleaners that are safe for rubber and plastic parts. Aggressive solvents can destroy the membranes of the accelerator pump.
The training process includes:
- 🛠️ Dismantling of air filter: Remove the air filter cover to access the carburetor valves.
- ⛽ Shutdown of the fuel line: close the crane on the fuel tank and disconnect the hose from the carburetor, substituted the tank for draining the remaining fuel.
- 🔌 Unconnection of cables: carefully disconnect the throttle control cable and the air thrust, remembering the order of their installation.
It's important to have good lighting in the workplace. Small parts like springs and screws are easy to lose, and work better on a clean surface covered with white cloth, where you can see the fallen elements.
Step-by-step instructions: disassembly and cleaning of the carburetor
Carburettor disassembly process Tohatsu 5bhp First, you take the entire engine assembly off the engine, you unscrew the two nuts to the intake manifold studs, and be careful not to lose the insulating spacer and the gaskets between the carburetor and the engine.
Once you remove the carburettor on the table, unscrew the screws of the bottom float chamber lid, and inside you'll see a float fixed to the axle, squeeze the axle carefully with a thin embroidery or drill to release the float, and there's a shut-off needle underneath, check the needle sharpness, so there's no cross-hazard left by the valve seat.
☑️ Checklist for carburettor cleaning
The main cleaning shall be carried out as follows:
- Unwrapped the main jacklair and idle jetlar, which are located in wells inside the hull.
- Use an aerosol cleaner to blow through the channels under pressure. The jet must pass freely.
- Rinse the float chamber and the float itself. Make sure there is no fuel inside the float (seal check).
- Look at the membranes. They should be elastic, without cracks and bullies.
Pay special attention needle-valveIf you see the needle cone, you have to replace it, otherwise the carburetor will be transfused, and you're going to put the float in reverse order, and when you're mounting it, you need to keep it in position relative to the body, so that the fuel level in the chamber is consistent with the factory parameters.
Adjustment of mixture and idling quality
After assembly and installation of the carburetor on the motor, a fine-tuning stage follows. Tohatsu They are usually billed on the rotation of the screws, but engine wear and operating conditions may require adjustment.
First adjust the mix quality screw at low revs (usually located closer to the base of the carburetor). Wrap it to the point (without diligence!), then turn it to the base value specified in the manual (often it is 1-1.5 revolutions). Start the engine and smoothly wrap the screw, achieving maximum and stable idling speeds. Then set the desired speed of rotation of the crankshaft with the screw number of revolutions.
| Parameter | Basic setting (rotor turns) | Symptom of rich mixture | Symptom of poor mix |
|---|---|---|---|
| Idle passage (L) | 1.0 - 1.5 | Black smoke, stained on a candle | Engine's stalling, not keeping pace. |
| High RPM (H) | 1.0 - 1.5 | Power drop, overspending | Sharp sound, risk of overheating piston |
| Turnover XXX | 950-1050 rpm | Vibration, low frequency | Too high a turn on neutrals |
The secret to fine-tuning
When adjusting the screws of the mixture, use a tachometer. It is difficult to determine the peak of revolutions by hearing, and the device will show the exact value at which the engine is working most efficiently.
Adjustment at high speeds (H screw) is done with caution. The screw twisted enriches the mixture, the screw twisted - impoverishes. The optimal position is when the engine develops maximum passport speed under load (on water). On land, you can not turn the engine at full speed to avoid overheating.
Typical service errors and their consequences
Inexperienced owners often make mistakes that lead to the need for re-repair or even major repair of the engine, the most common of which is ignoring the condition of the gaskets. Disposable gaskets when re-installed do not provide leakproofness, which leads to the fact that the gaskets are not properly sealed. air-suck.
The suction of unaccounted air after a throttle damper makes the mixture poor, causing unstable operation and overheating. Another mistake is using compressed air from the compressor to dry the carburetor without first purging the purifier. The water in the compressed air system can preserve the channels or cause corrosion of aluminum alloys.
⚠️ Attention: Never use a steel wire or brush to clean the jellycleras. Microscopic scratches will change the jellyclera's throughput, and the carburetor will become impossible to adjust.
Also worth mentioning is the float assembly error: if you set it wrong or break the geometry of the lever, the fuel level in the chamber will change, too high a level will lead to constant overflow and the engine will work on the re-enriched mixture, which can cause the piston group to fail.
High-quality sealing of compounds and a clean gasoline system are the key to a long life of the carburetor without the need for frequent adjustments.
Prevention and care of the fuel system
To have a carburetor Tohatsu 5bhp It's been a long time, and it doesn't require much intervention, and it's important to follow the rules of operation, because the main enemy of the carburetor is poor fuel, and the long-term storage of the gasoline engine in the system, and modern ethanol fuels are hygroscopic and when they are deposited, they form resinous deposits.
It is recommended to use gasoline with the octane number recommended by the manufacturer (usually AI-92), and be sure to add quality two-stroke oil in the correct proportion. Before a long parking (winter or off-season), it is better to develop the engine completely or drain the fuel from the carburetor.
Regularly replacing the fuel filter-sludge will also prolong the life of your carburetor. A fine mesh will delay a large fraction of the dirt, but fine particles pass further and settle in the chicklers. Timely replacement of the filter-rough cleaning is a cheap way to avoid expensive cleaning.
Questions and Answers (FAQ)
Why does the Tohatsu 5 carburetor leak gasoline out?
This is most often indicative of leaky shut-off valves, whether it's sand pollution of the valve seat, needle cone wear, or misadjustment of the float level, or deformation of the float itself.
How often should I clean the carburetor on the outboard motor?
When using high-quality fuel and regular operation, preventive cleaning is enough every 2-3 seasons. If the engine is without work for more than 2 months, it is recommended to drain the fuel or use a stabilizer.
Can I adjust the Tohatsu carburetor without a tachometer?
Rough tuning can be done by ear, achieving stable idling, but to fine-tune high speeds and prevent dangerous poor mixtures, the presence of a tachometer is highly desirable.
What to do if the screws of the adjustment of the mixture are twisted to the point, and the engine is trembling?
Most likely, the carburetor channels are filled with resinous deposits or there is air sucking through the gaskets, you need to remove the carburetor, make a complete defect, clean with ultrasound or chemistry and replace the gaskets.