Short instruction manual for JetSurf operating

Edited on 26.02.2025

As with any small-scale equipment, it requires certain rituals to minimize expenses on spare parts and repairs.

Original JetSurf Manual

Before the First Start.

Preparing the Fuel Mixture.

The fuel must always be mixed with oil. The basic ratio is 1:50 (older tanks indicate 1:25). That is, 200 grams of oil per 10 liters of gasoline.

A single start without oil may not immediately damage the engine but will significantly reduce its lifespan.

Do not use quick start on a dry engine! It will seize the cylinder!

Fuel mixed with oil always has a color (reddish, bluish, greenish, etc.). If the fuel is colored but you're not 100% sure the color is from the oil, do not use it, as the gasoline itself may be colored due to additives (it's better to mix a new batch).

Starters – A Weak Point.

If the engine doesn't start after 4-5 attempts, take a break for a couple of minutes and try to identify the problem (fuel hasn't reached, no spark, flooded spark plug, etc.). A functioning engine should start immediately.

If the board has been idle for a long time and the engine is dry inside, you can pour a few grams of gasoline through the carburetor.

Additionally, during startup, you can cover the carburetor opening with your hand (this will help fuel pump faster).

If the engine doesn't start at all, refer to the troubleshooting guide (high-quality version here)

Spark Plugs

Check the spark plug; there are two types:

• Long BPR7HS NGK with a 5K Ohm resistor, installed on newer model heads (black color).

• Short BPMR8Y NGK with a 10K Ohm resistor, installed on older model heads (gray color).

Installing a spark plug with a different resistor rating will result in:

• At best, the board will start but stall when throttling.
• At worst, the CDI unit in the electronics block will fail.

Additionally, checking the spark plug for a spark with poor grounding contact can damage the CDI unit (attach the plug to the engine with a clip or place it firmly on the engine).

With our blocks (Mudretsov), you can use any spark plug (with or without a resistor). The most important is to match the thread length and heat rating (the number in the spark plug model).

Carburetor Settings

Fully tighten both screws, then:

• The screw closer to the jet pump: unscrew 1 turn + 1/4 turn (1 hour 15 minutes).
• The second screw (further from the jet pump): unscrew 1 turn + 3/4 turn (1 hour 45 minutes).

Carburetor settings for Sava/Kootu

Charging Settings

JS batteries are assembled from 18650 cells in a 3S2P (square blocks) or 3S3P (cylindrical blocks) configuration.

This means three cells are connected in series, with a maximum battery voltage of 12.6V.

Charging is done in Li-Ion or Li-Po mode with a current of 3.0A (maximum voltage 4.2V per cell).

• ! For square blocks, connect the balance connector to the charger; for cylindrical ones, it's not necessary.

On Sava motorized surfboards, the block has a voltage of 4S (16.8V).

Operation on Water

The engine is not susceptible to hydraulic lock, and if flooded with water, there's no need to immediately grab a spark plug wrench:

• Turn off the board, remove the magnetic key from your wrist.
• Place the board on its side, with the carburetor or injector facing down.
• Manually rotate the crankshaft several times (water will pour out through the carburetor).
• Once the crankshaft rotates normally, you can turn on the board and try starting it (still on its side, carburetor down).
• When starting, fully open the throttle; the board should start on the second or third attempt.
• Keep the throttle open to blow out water from the muffler (5-10 seconds).

Freewheel

If, during startup, the starter turns the engine normally, but the number of compression strokes is noticeably reduced (slippage is felt), take a phone and record the jet pump clutch in slow motion.

If it rotates unevenly (or is thrown back), it's time to replace the freewheel.

The sooner this is detected, the higher the chance to save the crankshaft journal.

After Riding

After riding, the board should be started on the shore in a vertical position (with the muffler facing downward) for 5-10 seconds. Then, leave the engine compartment open to allow the internal space to dry completely.

If the board was used in saltwater, it is necessary to rinse off the salt with fresh water (both the exterior of the hull and inside the engine compartment).

Additionally, the cooling system must be flushed with fresh water while the engine is running, and then blown out without water.

A hose for this can be assembled from parts available at any plumbing store or purchased from us.

If you forget to do this or simply feel too lazy, remember: a new piston group, cylinder, and half of the crankcase cost at least €1,500.

And it only takes a few days for saltwater in the engine to cause irreversible damage.

Storage

The electronic control unit should be stored in a warm place and periodically charged (every 2 months).

If the charger shows an error for any reason, switch the mode to Pb (for lead-acid batteries).

Set the charging current to 1.0A

Select 1S (single cell)

Disconnect the balance connector (the white plug with six wires)

If charging still doesn't start with these settings, check the wires and their connections again. If nothing helps, it's time to replace the battery cells.

If charging begins in Pb 1S mode at 1.0A (2400mV per cell), wait 5 minutes, then switch to 2S, and after another 5-10 minutes, switch to 3S (all in Pb mode).

Finally, return to the standard settings:

• Li-Ion or Li-Po, 3S, and 3.0A

You can repair your motorized surfboard here: JetSurf Workshop of Georgy Mudretsov.