Need help with carb adjustment

[Jaiello]

I just finished the restoration and rebuild of my 2001 Sea-Doo xp. New crank, pistons, bore out .5 over. Rebuild carbs with mikuni kit. Went thru the whole ski. Gel coat was oxidized to hell and back sanded it with 800, 1000, 2000, running compound, polish and waxed. I now have two things left get it on the trailer and go get a key programmed. Primed oil pump and filled it up with gas and put some oil in there for the break in. My question is my carbs have two adjustments on the top and one on the front side for the idle. What is the procedure for the first run? I had to replace the throttle cable because it was sticking the idle screw doesn’t touch the stop now but I think the previous owner messed with the adjustments and having a stretched out cable he probably had to mess with it. What is the adjustment for the two top screws ? Any help is greatly appreciated. I have had a blast rebuilding this ski. Can’t wait to go try it out.

 

[JeremyD615]

The hulls turned out nice! I’ve always liked the grey on that model...

 

[Jaiello]

Thanks for all you guys help this forum has been a great help when I have gotten stuck. It turned out great I wish I would of taken pictures of the before this ski bent a piston rod. Overheated and was left in the yard for over a year and a half. It was rough. It’s amazing what a little elbow grease can do. Thanks again.

 

[mikidymac]

You want the idle a little low on the 951 or they will runaway on the trailer.

I wouldn’t set it anywhere over 3000.

The low speed screws should be at 1-1/2 turns out on both carbs and the High speed screws closed on both carbs.

Assuming your ski is stock with stock airbox.

 

[Matt Braley]

His will run away because there is not enough slack in the throttle cable.

 

[mikidymac]

Mine never tries to run away, there could be air leaks or idle mixture might be too lean if you have this issue.

Even with slack in the cable and everything perfect the 951's are known to run away if the idle is set too high. I am sure it has to do with the 46i carb and them being more of a lean ski for emissions.

Just don't set the the idle over 3,000 and you should be fine.

 

[mikidymac]

Runaway is indicative of fuel system issues, air leaks and such.

You are wrong on the 951. It can be perfectly fine and run away if the idle is set too high. I agree with you on all other engines, just not the 951 in particular.

Here is from the late great Bill Oneal even if you don't believe me.
"
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 pulse 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"

 

[drjack]

Mine was happening because of comment #7. The gasket was very thin material to start with. Found out during my recent carb overhaul you could obviously notice the squish pattern of the base gasket, there was a small area not compressed and allowing air to pass.

 

[mikidymac]

Yes, the 951 is a finicky beast but it sure fun when they are running correctly.

When I first got my 2001 XP the engine was out and it was perfectly air tight, 8 psi for 2 hours and not a single psi lost. Carbs and fuel system completely gone through, replaced and rebuilt. I set the idle at 3,000 like all my skis and the first time I touched the throttle in the driveway it ran away. Pulled the carbs and checked everything again, 1211 on the carb gaskets and the same exact thing, runaway. Pulled them a 3rd time checked everything once more and found absolutely nothing. New carb gaskets again and same thing. Got on google and found the article by Bill Oneal on the 951 and the idle having to be at 2800 and never had a runaway again and has been running perfect for years now.

So the moral of the story as most, try the simple things first before getting crazy. Adjusting the idle is about as simple as it gets, if that doesn't work then move to the next thing.

 

[mikidymac]

2-strokes need their fuel, set too lean or carbs jetted too lean, air leaks, etc. they have bad manners and nasty things happen. This is true for all 2-strokes. That familiar 2-stroke outboard "sneeze" you hear at the marina? Too lean.

The correct way is add fuel until it's obviously too much then slowly back off just enough to clean it up. Done. This holds true when rejetting, as well.

I agree the 951 factory calibration is too lean or I should say, not rich enough for me by just a little.

I totally agree with you Sportster. the issue is the 46i carb itself on the 951. If you get it rich enough on the lows to stop the runaway then you will have issues with it being too rich at idle. So... the easiest fix to make everything happy is to just set it at 2800 rpm instead of 3000.

This is only assuming you have no air leaks, dirty jets, or other issues. Also this only applies to the 951 runaway. All other skis if you have a runaway you have an issue described by Sportster.


Trust me, the first time you have a runaway you will crap yourself and swear the world is coming to a crashing stop when it is wide open and the lanyard and kill switch do nothing. Nobody wants that.