still having problems with my 720 spx

jetski9010 · 12-23-2009, 10:11 PM

I was having problems with this ski last summer. It would die if you went to full throttle and sometimes would die even at mid range throttle also. I changed out all the fuel lines and had the carbs sent to watercraft magic for cleaning/rebuilding and the jetting update kit with the filters. I just took it out on a test run again today and still does the same thing. I cant figure it out if it is a fuel problem or not. Could there be an electrical problem I could be having that would cause this. If not the only thing I can think of is if its sucking air into the fuel system somwhere or if the crank seals are bad. It doesnt act like it has a dead spot down low or anything it will just fall on its face if you take off. Sometimes it will go 100 yards before doing so and sometimes 100 feet.

faster7581 · 12-24-2009, 09:05 AM

check compression, pull the the plug caps off, trim the wires back 1/2 inch, and thread them back on, repalce the plugs and give that a shot

jetski9010 · 12-24-2009, 10:57 AM

alright what is the good compression range?

Mr. Bill · 12-29-2009, 08:09 PM

150 psi or better. Did you clean out the fuel selector valve ?

If you cannot figure it out and suspect it may be carb related, send those carbs back to our shop with a note explaining what the SPX is doing wrong. We will not charge you for taking another look at them dissasembled at our shop if you paid us to repair them and they do not function properly.

Mr. Bill · 12-30-2009, 07:16 PM

And remember to include contact information this time.

If you recently did any other work on the motor or replaced the fuel lines, it is possible that you have one or more of the fuel or vent hoses on the wrong nipple of either the fuel baffel, the selector valve or the carbureator.

On the upper part of the baffel near each nipple, there is a marking that will be RES, ON, RET, or VENT. It can be hard to see it when installed in the gas tank as the markings are on the side, upper part of the baffel near the fittings. Both vent lines connect together and go to one fitting marked VENT. Be sure the vent lines are not kinked and that you can blow air into the vent line gromment and hear it going into the gas tank. I use compressed air from our air compressor and watch for the gas tank to swell up a bit. It only takes a very short blast of air into the gromment up on the deck to see the gas tank swell. Too much compressed air will damage the tank or blow apart the forward fuel filter assembly, or push a hose off of one of the fittings.

Other common errors when swapping out old fuel lines is reversing the on line and the return line at the carbureators, or the on line and reserve lines and OUT line on the fuel selector valve. The fuel selector valve fittings are also imprinted on the fuel valve body.
So, the ON line goes from the fuel baffel fitting at the gas tank, to the on fitting on the fuel selector valve. Be sure all three passages inside the fuel valve are not clogged up. The RES line from the RES fitting on the fuel baffel goes to the RES fitting on the fuel valve. Coming off the fuel valve OUT fitting, the fuel line goes to the forward fuel filter to the IN side. The OUT fuel line from the filter assembly goes to the fuel pump fitting on the carbureator. That fitting is always next to the fuel pump and the lowest fitting on a Mikuni carbureator. Both carbs are linked together by two hoses with a plastic Y fitting at the end of the two hoses. This is the return line fitting at the top of the carbureators. It goes directly back to the top of the fuel baffel fitting that is marked RET.The other hose connecting the two carbs together is the fuel transfer hose to feed the carb that is without a fuel pump on it, usually the rear carb has no fuel pump, only the front carb, except on 1997.5 GSXL's, Where Sea Doo decided to try revesing the two carbs on the intake manifold. This is only on white 947 engines.

If you are looking down at the fuel baffel from the top, there are 4 plastic nipples. Once you know where any one of the 4 nipples is and where it goes, you can easily figure out where the other three attach. The VENT and RET lines just go into each of their fittings but do not extend past the top of the fuel baffel as one just dumps air into the tank to vent the tank or relieve pressure in the tank if it builds up too high, and the RET line just dumps unused fuel back into the gas tank from the carbureator. Those two fittings are opposite of each other on the top of the baffel, while the ON and RES are also opposite of each other on the baffel. So, lets say that you identify one of the four fittings on the top of the baffel and it is the ON fitting. Knowing that, you will know that the very next fitting on either side of it going from left to right or right to left, is either the RET or VENT fitting and those two are identical in function and it would not matter if those two hoses were connected to the wrong fitting. i.e. if you mix those two up, it doesn't really matter. But they cannot be connected to either the RES or the ON fittings, nor can the ON hose be connected to the RES fitting and vise versa, you cannot connect the RES hose to the ON fitting. The third fitting of the 4 will be the RES fitting in this example, as it is opposite from the ON fitting orientation on top of every fuel baffel.
When I was wrenching on these things everyday, I knew which of the four fittings was just to the right of the two pink wires. Lets say it was the ON fitting. In that case, the very next fitting, if you go from one fitting to the next one inline around the pattern of fittings is either the VENT or the RET. The next one will be the RET and the last one of the four will be either the VENT or RET fitting, and it won't matter if you connect one of those two to the wrong fitting as I said, they both just dump into the very top of the tank baffel and have no extensions to pick up fuel from near or at the bottom of the baffel. The RES tube into the gas tank baffel is always the longer of the two tubes that pick up gas from the lower part of the gas tank. The on tube is always the shorter of the two extending into a gas tank.

If a hose is connected to a wrong fitting ( with the exception of the RET and VENT hoses being reversed with each other ), it can cause the motor to accellerate for a second or two before running out of fuel and falling on it's face. The same happens if no air is entering the gas tank as you suck fuel out of the gas tank. That will stop the flow of fuel out of the gas tank in a short period of time when riding the pwc. The length of time depends on the fuel level in the tank. If it is low on fuel, there is more air in the tank above the level of fuel and it will take a bit longer before the motor stalls.

The next possibility is that the oring is missing from the top of the fuel filter bowl. If that happens, the fuel pump will suck air from the fuel filter assembly and not get enough fuel into the carbs to sustain higher rpm. The carbs will run dry of fuel and the motor will stall out at higher rpm. It may or may not completely die out if you let up on the throttle. It might still get enough to keep running at low rpm, but accelleration is not possible for more than a few seconds at best.

If your problem is inside the carbs, it will show up by the way the sparkplugs look when it stalls out. If they are wet with fuel, it may mean the high or low speed adjusters are opened too far from closed, or it may be an internal problem inside the carbs or fuel pump.

Make sure your pulse line is in good shape. If it has a hole or kink in it, it will not provide enough pulse to pump enough fuel to the carbs.