Bogs off idle when warm

[Jim Dawson]

I have a 97 Challenger that revs right up at first (usually) but after a few minutes of running, if you slow it down it really bogs when you nail it coming off idle. It might take 30 seconds before it hits 3000 rpm, then it revs right up to full speed. I had the carbs rebuilt but nothing changed.

 

[kustomkarl]

Welcome to the seadoo forum Jim. I own a 1997 Challenger too, with a single 787 engine. It sounds like the accelerator pump isn't pumping fuel at the bottom of the rpm range. To check it pull off the carburetor air box and sparkarester. Look inside the throat of the carburetor. You'll see a small brass tube sticking down into the carb. As you push the throttle cable forward as if to accelerate. It should squirt a small amount of gas into the throat of the carb. If it isn't, than you need to pull the carbs off and clean the accelerator pump lines from the pump to the carburetor throats. In the carbs is a small valve that gets clogged real easy. Pull it apart and use compressed air to unplug it. Do you have a repair manual? it would be a huge help. If you want you could join as a "premium member". As a premium member you can down load a authentic seadoo manual from the seadoo manual library. In the library is a variety of manuals for almost all years and models. You can view as many as you like on line as a PDF file, or download it and print it for your personal and privet use. There are operator manuals and repair manuals for you to do your own repairs on your seadoo. The repair manuals have everything from troubleshooting, repair procedures to winterizing. It contains wire diagrams torque specs and pictures for disassemble and assemble instructions. In the spec sheets it tells everything needed to maintain oil changes, spark plug gaps, carburetor rebuilds and impeller wear ring tolerances. Click on the "Seadoo Manuals" link at the top of the page for more details. If you need any help or get in a jam, we are always here to answer your questions too.

Karl

 

[Jim Dawson]

accelerator pump

Thanks, I'll take a look. Is the accelerator pump internal to the carb and should I see the squirt on both carbs? I saw a little black item hooked to the throttle cable near the PTO end of the motor. Is that the pump?

I question whether lack of accl pump is the issue since the problem gets worse when the engine is warm. Also, to rule this out a couple days ago I pulled the intake cover and flame arrester off once the engine was warm and it started bogging and sprayed a shot of WD40 in the carb and it didn't help it rev. Next I tried a shot of either (with cyl lube) and it didn't help so to me, that rules out fuel shortage as the problem. I had the carbs rebuilt by a shop that supposedly knew what they were doing at the end of last season and it didn't change anything. I would think that they would have addressed any plugging.

 

[Jim Dawson]

accelerator pump

Thanks, I'll take a look. Is the accelerator pump internal to the carb and should I see the squirt on both carbs? I saw a little black item hooked to the throttle cable near the PTO end of the motor. Is that the pump?

I question whether lack of accl pump is the issue since the problem gets worse when the engine is warm. Also, to rule this out a couple days ago I pulled the intake cover and flame arrester off once the engine was warm and it started bogging and sprayed a shot of WD40 in the carb and it didn't help it rev. Next I tried a shot of either (with cyl lube) and it didn't help, so to me, that rules out fuel shortage as the problem. I had the carbs rebuilt by a shop that supposedly knew what they were doing at the end of last season and it didn't change anything. I would think that they would have addressed any plugging.

The plugs pretty good so I'm not thinking it's ignition either. If not air, fuel, ignition, that leaves me with exhaust. Can you get too much water in the water box or does exhaust just blow that out instantly?

 

[kustomkarl]

Jim, Have you cleaned you RAVE valves in the last year or so? If not let me explain the RAVE valves. The RAVE, (Rotax Adjustable Variable Exhaust) valves are located above the exhaust valve. There are 2 of them per engine. They are round with a red adjustment screw in the middle. It has a clip that holds it together. How they work is that they open the exhaust port larger as the engine rpm's increase. When the rpm's drop down so do the RAVE valves. They work on the principle of the pressure of the exhaust system. Rpm's increase, pressure increases and the valve opens, rpm's drop pressure drops, Valve closes. They should be de-carbonized annual. To disassemble the rave valves, remove the spring clip on top, remove the black cover. There is a spring under the cover. Remove the piston by turning it with a metric socket. On the bottom of the piston is the rubber "Bellows" be careful with the small retaining spring that hold the bellows on the piston. Remove the 2 allen screws that hold the base on the cylinder. Remove the base and gasket. The long valve won't fall in the cylinder just pull it out. There is an o ring under the base, on the shaft of the guillotine valve. Be careful to see how it came apart as it has to go back together that same way again. On the base, notice the notch that it is facing down. Clean all the carbon off the guillotine valve. I use carb cleaner and 400 grit paper. Check the bellows for any small pin holes. If so replace it. If not, reassemble it on the clean guillotine valve, and install it back on the engine the same way it came apart. The guillotine valve only fits one way. The one closest to the exhaust pipe will come off differently then the other one. You will have to remove the allen screws and turn the base so it clears the exhaust pipe. I would do one at a time in case you forget how it goes back together again. This way you can look at the other one and copy it. Do both engines 2 per engine. Take your time and if you have questions give us a shout. We'll be here to help you out.
If the RAVE valves are dirty it will not rev up correctly and could be causing your problem.

The adjustment knob (the red cap) should either be screwed all the way in or flush to the top of the black ring of the cap. This will only affect performance, as far as how it jumps out of the hole or how well it runs for extended periods at WOT.

This might be your problem if you haven't cleaned them in a couple years.

Karl