155-SPK

Yamaha GPR1200 Flow Control Adapter Kit
Yamaha XL Limited 1200 Flow Control Adapter Kit

Our adapter kit is designed to improve bottom end response and get the craft into high speed quickly and gives more acceleration out of turns.

By allowing the craft to get up on plane quicker, less time is spent pushing or plowing the craft through the water. This is especially true on the XL models. The quicker you get the craft up and on the water, the quicker the boat will accelerate because you can use or free up the horsepower that is  being used up to displace and push aside the water. The water drag - frictional loss of the wetted surface - is reduced and this is when the craft actually starts to really accelerate.

One of the main reasons the GPR and XL are sluggish or experience a lag on acceleration is due to the large amounts of water that enter the water box. This water backs up in the water box and hoses to be purged or blown out upon acceleration, The water box can hold a considerable amount of water. This can not be purged out easily since the hoses and resonators are located at a higher level then the water box. The water must be pushed upward and through the resonators. Since the water box is fairly large it can hold a good amount of water. It is not until all this water is blown out that the exhaust can be free flowing. During all this time the craft is trying to get on plane which causes more load on the engine and further lengthens the process.

Three of the reasons that further complicate this problem are:

1    The fact that the amount of water needed to cool the exit hoses has to be greater than normal because of the extra heat generated by the catalytic converter. You have to have a large amount of water to quickly cool the gasses, especially if you are also using plastic acoustic resonators right after the water box.

2    Large amounts of water being flowed at idle due to the fact that the spray points or bleed holes are located at the lowest portion of the water jacketed exhaust. Gravity is itself helps push more water through these orifices mainly because the cooling line exit hose is located at the highest point of the exhaust systems water jacket.

3    When all this water is trying to be pushed out of the water box upon acceleration, resonators and exit hoses, we are also adding even more water because of the increased water pressure in the water jacket imposed by the pump impeller during acceleration. We must remember that the water pressure in the water jacket raises instantly, since there are no air pockets and water can not be compressed. This happens the split second that the pump pressure is increased. The blowing out of the water or cleaning up period is increased because we are further injecting water at higher pressure during the time we are trying to blow out all this backed up water and at the same time trying to get the craft to plane and maybe even trying to pull a skier, knee boarder or wake boarder.

If you pull skiers, then you know the drag created when pulling a skier out of the water. Once the boat is on plane and the skier is up, this drag is significantly reduced. So, getting the boat on plane quicker will mean less time spent in the inefficient transition period just before planing. This allows you to pull up the skier faster and allows the craft to handle even heavier skiers.

How does the FC Adapter Kit work to eliminate this problem?

What we do is to block the water reaching the original spray orifices and use a water pressure sensitive flow control valve to control when water is injected through the OEM stinger outlet. By using this kit, you can preset the RPM when you want the water to start flowing. By setting the RPM point to 3400 RPM, you have eliminated the water flow at idle and in a sense have a dry water box upon acceleration. The craft can now get on plane quicker and accelerate much, much quicker. We don't need water flow below these RPM's mostly because the firing pulsations are too weak and too far apart to create any considerable heat at this location (too far away).  This also increases acceleration in the mid-range to upper mid-range and greatly improves acceleration coming out of turns. this is accomplished primarily because we also have completely shut down the water flow through the orifices in the OEM stinger outlet at the moment of deceleration.

(NOTE: this kit is designed to be used on watercraft that have the catalytic converter removed and are also using a straight tube in place of the plastic sound suppression resonators.)

There are two kits available:
The 155-SPK kit requires the removal of the cooling system overheat sensor.
The 155-SPK-TS kit retains the overheat sensor but requires you to drill and tap the water jacket of the exhaust system and install a calibrated bypass fitting on the craft. This kit comes complete with all the bypass fittings, hoses, tees and clamps.

The 155-SPK kit can be installed by simply replacing the gasket at the OEM stinger outlet and installing our gasket. Removing the overheat sensor from the OEM stinger outlet and install our new fitting where the sensor was installed, install the tee, restrictor and flow control valve to supply water to this fitting.

Both kits allow you control at what RPM point you start to inject water and you can control the total volume being injected by the use of a Mikuni main jet at the stinger fitting. Adjusting the RPM point is as simple as turning the outer housing on the flow control valve.

The performance gained by installing our  flow control adapter kit along with our catalytic removal plate and flow tube is dramatic. If you add these items along with our air filter kit, carburetor re-jet kit and aftermarket impeller, the craft will accelerate very quickly and come out of turns without bogging or hesitating. In fact, it will perform as good or better than other crafts with much more expensive modifications such as exhaust outlet kits, aftermarket C.D.I's with more aggressive timing curves and aftermarket cylinder heads with increased compression.

A 4mph gain can be obtained on pump fuel and without an increase in compression or ignition timing.

If your craft is stock, we recommend our catalytic removal plate (part # EXP-155) to remove the catalytic converter and our flow tube (part #EXT-155G)for the GPR and (PART #EXT-155X) for the XL. The flow tube replaces the plastic sound suppression resonator.

The flow tube replaces the plastic acoustic resonators after the water box. These resonators are used to further quiet down the vehicle but they also impose resistance to the exhaust flow. They can also hold some water in it's cavity.

By installing the flow tube you now have a straight through design that offers better acceleration with a very minimal increase in noise.

NOTE: You must use a sensor chip (part #OHS-100) if the overheat sensor is removed.

The YE-155P is used to replace the catalytic converter. Instead of off setting the exit like the D plate on the non US models, the Jetworks cat removal plate has the exhaust exit centrally located to keep the velocity of the exiting exhaust gasses. This promotes better mid-range and upper-range pull.

The exit hole is closely matched to the stock OEM exhaust exit diameter. This keeps the proper back pressure thorughout the pipe and helps pull the most potential out of the stock exhaust system.

Jetworks cat removal plates are mad out of corrosion resistant stainless steel.

The removal of the catalytic converter greatly reduces the heat inside the engine compartment and allows you to be able to use aftermarket spark arresters with better results. The use of the aftermarket spark arrester is not recommended unless the added heat from the catalytic converter is removed.

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