2000 RX Lean

[etemplet]

I rebuild the carbs and did a new top end on the RX. Only rode it twice. I know it is lean as it tried to run away when I started it on the trailer but this didn't happen the other times I started it. When I get off the throttle it takes a couple of minutes for the idle to settle down to a consistent idle. It slowing drops from about 1300rpm to about 950. I'm pretty sure I don't have intake leaks I checked this thoroughly. I suspect maybe I have the Pop-off set too high or the accelerator pump may be leaking. I am going to remove the carbs and go over everything. Strange as I've not had a ski do this previously.

The run away began as I started the ski. I didn't let it idle very long maybe 10 seconds. When I opened the throttle a bit it tried to kill. I played with the throttle a few pumps then zoom. I figured it just didn't have enough fuel feeding the engine at the time. After water testing.... I'm comfortable that something isn't where it needs to be.

I plan on lower the pop-off and checking the accelerator pump. I'll look really hard at the carb intakes when I remount them. I will probably replace the fuel valve if that one isn't new. Am I missing anything?

 

[etemplet]

Okie Dokie, I pressure tested the carbs as removed. Fuel pump seems to be working very well. No leaks or bubbles from the carb soap test at 10psi (help pressure very well). Carb to intake Gaskets looked good, no signs of leaking. Low Speed adjusters are at 1-1/2 turns out. I am going to check pop-off on both carbs. Having just rebuilt them they should be spot on. I'll put the pop-off close to the bottom number. Basically I see no problems with the carbs so far.

I will pull the accelerator pump and have a look.

I know a tightly adjusted throttle cable can cause these carbs to hang up and my throttle cable does take some thumb power but it works well and closes completely. I may replace the cable.

Gonna pressurize the fuel system to check for leaks.

Touchdowns everyone.

 

[GGuillot]

I am going to check pop-off on both carbs. Having just rebuilt them they should be spot on.

Why didn't you check the pop off when you rebuilt them?

 

[mikidymac]

Pretty common on a 951

Bill's top 12 causes of runaway 947 engines.

1. Most common reason is out of the water and the idle set just 100 to 200 rpm too high. The confusing part to a 947 newby is that all other 2 stroke Sea doo engine models are set to 3000 rpm out of the water, but a 947 idles perfectly in the water when you set the idle speed at 27-2800 out of the water.

2. Allowing the head to get too hot becuasue it is running without water going through the motor when on the trailer.

3. And some of these next reasons could be a toss up in order, Replacing the carbs onto the engine for whatever reason and setting up the throttle cable adjustment too tight at the carb cable bracket, leaving the throttle plates slightly cracked open.

4. Clogged or partially clogged low speed jets.

5. Low speed adjusters are set too far in, not allowing enough fuel to pass at idle speed.

6. Water in the gas tank that ends up inside the carbs blocking fuel flow through the jets.

7. A poor job of keeping the carb base gaskets aligned when replacing the carbs onto the manifolds equals an air leak.

8. A pin hole or split in the plastic tubing that connects the engine case pressure fitting to the check valve in the rave valve pressure supply line, or a broken check valve in that same line. This allows air to go into the engine during up strokes, leaning out the mixture.

9. One stuck needle valve that will not open.

10. Rust inside the carbs, see #6.

11. A pin hole in the fuel pump pluse line.

12. A rod hanging out the side of the cases ( or just any crack or hole in the cases ). Do not laugh, I have had customers come in saying they needed a "tune up because the motor runs away on them " only to point to that rod hanging half way out of the motor and the lower case half nearly sawed in two.

Bill O'Neal
WCM

 

[etemplet]

LOL..... good info. Gonna be simple I expect. These engines are tedious to set idle in the right place. I'm gonna fatten up the Pop-Off first thing and go from there.

It was lean when I was adjusting and I believe it was just a chain of events but I'll leave nothing to chance. Fatter is better but not too fat. Being an old two stroke guy I recognize all the symptoms. It's taking it's time coming down to a constant idle in the water and I don't see where it is the throttle cable. I was careful to set that correctly as I have encountered this previously when setting up other 951s with carbs. This engine seems hanging at idle.

 

[etemplet]

All checks went well. I even tested the release pressure and check pressure on the accelerator nozzles. Accelerator pump looks great, working like a champ. Only about 1 hour on the engine after the work so all this should have been spot on. I just wanted to check. I'm gonna call this a stiff throttle cable issue. The adjustment was good but I think it just took too long for the butterflies to close after bliping the throttle with no load on the engine.

Gonna replace the throttle cable and call it done.