98 GTS runs great with the choke 1/2 way out

[Venturian1]

A little reluctant to start when cold, idles fine, revvs up when out of the water, runs ok at 1/4 throttle, but towards the top, it hesitates. I found that pulling the choke out a little it takes off and winds out nice. But I would rather keep both hands on the grips.
This carb has an accelerator pump, and I tested the diaphragm and check valves, and the restricting orifice on the input side that's in the small fuel hose.
Pop-off pressure within 35-42psi, fuel pump check valves both holding, correct jets and needle & seat is 1.5, and the arm is level with the bottom. could the lack of fuel be caused by not enough restriction in the return fuel line? I opened the high speed mix screw 1/8 turn it got worse. I put a hose pincher on the input side of the acc pump, it barely ran. I removed the tiny restricting orifice, no difference. Base gasket new, fuel hoses all new, screen in carb clean.
I know Y'all are smart. Any Ideas?
Oh, I lowered pop-off pressure to 25 - 30psi which improved it by raising the point at where it starts hesitating (crapping out), a little.

 

[etemplet]

Check the 3 small ports in the carb throat and also check the larger one for flow. You'll have to pull the low speed jet and shoot some lectra clean in there to check the flow. You should see 3 strong streams down the center of the carb and when you cover them the larger port on the left should flow well. You'll need to put the low speed adjuster in a few threads or you won't be able to see the flow as well. Having the low speed adjuster in there helps it pressure up a bit when you spray. Use the plastic tube on the can of lectra clean. If you shove it too far in the low speed jet hole you won't see as good a flow. You'll have to back it out a bit. Wear safety glasses and keep your mouth closed. LOL

What is likely happening is your transition isn't working and High speed circuit is fine because when you added fuel it got worse up high so you were too rich. There are different circuits in these carbs. Good Luck !!

 

[Venturian1]

Thank you for the help, carb is about to be disassemble again, I will do this. The reason for the pop-off pressure test to get the correct spring pressure on the needle arm, no? And, during engine running, it's the big diaphragm, that when pulled in by vacuum (from opening the throttle) pushes on the needle arm, which raises the needle off of its seat, thus allowing more fuel to enter the chamber where the main jet is located, where it is sucked into the incoming air stream of the carb, by way of venturi, no? So, I don;t understand why there are such a wide variety of pop-off pressure settings. Vacuum is directly related to compression, don't all new 717's have close to the same amount? The stronger the spring's resistance, the more vacuum it's going to take to overcome that resistance to open the needle valve, no? Throttle response would be slower with a higher pop-off pressure it seems. It's obviously running lean at the top end because pulling the choke out just a tiny bit fixes it, when riding.
If it had a float bowl, and the main jet is the correct size, raising the fuel level in the float bowl would seem like the thing to do, or raising the needle on a slide. Is raising the pop-off pressure kind of like lowering the float bowl fuel level? I'll do as you suggest and make sure all fuel passages are clear first. I always blow out all holes with brake parts cleaner with the carb totally disassembled, and there's two tiny holes near the throttle plate, which I assume are idle circuit via the low speed mixture screw passage, and the 3rd hole is in the main jet venturi which draws in fuel through the main jet, so if clearing all of these holes doesn't help, I'm thinking of trying a larger main jet.
This engine is new to me, bought a ski just to pull this motor and put in another ski, and when I bought it, the carb was off and apart in a bag.
It's never run right since I've owned it. had 150 psi on both cyls so I figured it would be fine, eventually!

 

[etemplet]

You can have "other than carburetor" fuel problems as well. Leaking fuel selector, leaking water separator, fuel lines that are not rigid enough (I had that problem for the first time a few weeks ago). What I do is go by the factory settings on the carbs. They should work at those settings with minor adjustments. To me, if opening the high speed adjuster helps.... you got a lean problem and it isn't the jets. Pop-Off adjustment can solve some problems but with the correct springs, good needle and correct seat.... Pop-Off is gonna be where it needs to be. Lowering Pop-Off will make your more rich at low speed and affect the high speed to a smaller degree. These carbs basically have 3 circuits. Idle (low speed) first 3rd of throttle, Transition, and high speed main jet. If you're bogging on the main jet you got a fuel delivery issue. Verify you have the correct seat size.
Good Luck !

 

[Venturian1]

Problem solved. not sure if it was fixed by cleaning out the fuel tank, installing the stock air cleaner, or blowing out the three holes in the lower section of the bore of the carb, (as etemplet suggested), I did all three before running it on the water again. So now it gets up to 50 mph, and this is on bumpy seas. It had an aftermarket air cleaner on it when I got it that was about 3" square, and 2" tall. If any water got slung around from the pto, some could have got into this air cleaner.

 

[Venturian1]

Problem was not solved after all. It ran great for two days, then went back to the s. o. s. (needing a little choke to fully rev up), and, surging occasionally like air getting into the fuel line, and very reluctant to start up when hot.
Checking the fuel filter, a few little foreign particles, and noticed the O-ring gasket looked like it wasn't making contact all the way around, so new O-ring, and no difference. So I ran across a carb off a 97GTi, without a fuel pump, rebuilt it, pop-off already set at 30psi, swapped carbs, and took it out for test run, and I love this ski again now. I've been through 2 full tanks of fuel now, it starts right up every time cold or hot, and gets full rpm, can do 50 mph on a bumpy ocean, and that's fast enough for me! Problem solved again.