Bad Check Valve SBN44?

[kawa js550]

I have a 650 Chicken that I recently went through the motor & carb. The ski runs really good but after riding when I go to start it again sometimes it doesn't want to start right away. I will have to to wait a minute or two and then it will go again. I thought that the needle and seat was leaking at first but I did not see any fuel dribble after I turn off the ski & it likes MORE fuel to get going again. I tested the pop off and the needle is sealing just fine. If I give it a shot of primer it will start right back up. It seems like when it gets turned off the fuel pump is loosing prime. I did replace the plastic check valves on the carb but manhandled them to get the rubber grommets on. Im starting to think I might have damaged them when installing.

What are the symptoms of bad check valves? I cannot find much info on this.

 

[WFO Speedracer]

I have a 650 Chicken that I recently went through the motor & carb. The ski runs really good but after riding when I go to start it again sometimes it doesn't want to start right away. I will have to to wait a minute or two and then it will go again. I thought that the needle and seat was leaking at first but I did not see any fuel dribble after I turn off the ski & it likes MORE fuel to get going again. I tested the pop off and the needle is sealing just fine. If I give it a shot of primer it will start right back up. It seems like when it gets turned off the fuel pump is loosing prime. I did replace the plastic check valves on the carb but manhandled them to get the rubber grommets on. Im starting to think I might have damaged them when installing. Also messed with the low adjuster and pilot jet and its happy where its at right now. Any more fuel and it doesn't like it.

What are the symptoms of bad check valves? I cannot find much info on this.

That sounds more like an air leak in the system somewhere, a loose connection or ill fitting fuel line , old dried out fuel lines , a bad one way valve on the fuel tank , a bad o-ring on the fuel filter, something along those lines is where I would be looking

 

[kawa js550]

That sounds more like an air leak in the system somewhere, a loose connection or ill fitting fuel line , old dried out fuel lines , a bad one way valve on the fuel tank , a bad o-ring on the fuel filter, something along those lines is where I would be looking

I leak down tested the motor and passed with flying colors. I thought it was the one way valve on the tank too but that checked out fine. I guess I could run a fuel line straight from the tank to the carb & bypass everything to rule the fuel system out.

 

[Harbor]

I was adjusting for a slightly too large of a pilot jet by leaning out the low adjuster for testing. Found the ski would not restart if you fell off or stopped to rest. Can’t remember the position, but 3/4 to 1 turn out or less I’d guess… so I opened the adjuster, think to 1 1/2 and it restarts now..

 

[WFO Speedracer]

I leak down tested the motor and passed with flying colors. I thought it was the one way valve on the tank too but that checked out fine. I guess I could run a fuel line straight from the tank to the carb & bypass everything to rule the fuel system out.

Not an air leak in the engine, an air leak in the fuel system itself , the fuel pump is just a pump , like any other pump if it can pump air instead of fuel it will do so .

The best way I can put it in laymans terms is sucking on a damaged straw in your drink cup, you can still get your drink out of the cup but it takes a lot more work to do so.

 

[kawa js550]

Not an air leak in the engine, an air leak in the fuel system itself , the fuel pump is just a pump , like any other pump if it can pump air instead of fuel it will do so .

When doing a popoff test I usually will bring the pressure just below the popoff pressure and let the carb sit to make sure that pressure is holding. It seemed to hold pressure just fine. I would assume that this is pressurizing the whole carb because I've had gaskets leak on the fuel pump side when doing this before.

 

[kawa js550]

I was adjusting for a slightly too large of a pilot jet by leaning out the low adjuster for testing. Found the ski would not restart if you fell off or stopped to rest. Can’t remember the position, but 3/4 to 1 turn out or less I’d guess… so I opened the adjuster, think to 1 1/2 and it restarts now..

Im at 2 turns out on the low adjuster right now. I went another half turn out and didnt notice much of a difference. Maybe I need to bump a jet size up so I have more room to tune my low speed adjuster. I might be having the opposite problem of you with a slightly too small of a pilot. Right now at a 115 pilot, could bump up to a 120

 

[WFO Speedracer]

Again I said fuel system, not carb, not engine, that means all the lines , filters , fuel selector valves and pickups that make up the fuel system , your idea of running a line straight from the carb to a fuel pickup is a good one and then you will know if there is an issue down the line somewhere, it is exactly what I do when I am tracking down an issue like this.

Think of it this way, you are siphoning gas out of something , if it gets air in the siphon hose at any point , either in the line anywhere or at the end where it is picking up fuel from it stops siphoning.

If you are two turns out I would go to the next size pilot for exactly the reason you just stated.

To answer your original question , damaged check valves usually still pump fuel but at a diminished capacity , this would show up on a wide open run , it would bog down like it was running out of gas because that is exactly what's happening the fuel pump would not be able to keep up with the demand for fuel.

 

[kawa js550]

Thx for the help. Sounds like these are my next steps.

1) Bypass fuel system with line going straight from tank to carb to verify I'm not sucking air into the fuel system.

if that doesn't work go to step 2

2) Bump up my pilot jet

I have no issues on the topend so I will rule out the check valves as a possible issue for now.

 

[fastgtfairlane]

Sbn44 on a 650 and you are using a 75 pilot jet? That is wayyyy too small. You need at least a 110-120 pilot and a 130-145 main. Popoff around 21-25 psi. Typical n/s for that is 2.0 with a 80g or 95g spring. Try both see which works best. You can play around with combination of popoff and low speed jet to get it tuned. Your low speed screw should be around 3/4 to 1 turn out from closed. I like my high speed screw to be 1/2 to 3/4 turn out so I adjust main jet according.

 

[kawa js550]

Not sure why I said 75 pilot but that is not right. Here are the specs per Jet Maniac recommendations.

135 main
115 pilot
2.3 N/S with 95g spring (im around 20-22 psi on popoff)

Im going to bump up the pilot to 117.5 or 120.

The high speed is two turns out already so after im done messing with the pilot I will probably bump my 135 main up to a 140 since I have one sitting around.

 

[fastgtfairlane]

What are you using as a flame arrestor? That will also affect popoff. Oem flame arrestor will need higher popoff typically than a open filter type. Try a 120 pilot 145 main and see what that does and go from there

 

[kawa js550]

What are you using as a flame arrestor? That will also affect popoff. Oem flame arrestor will need higher popoff typically than a open filter type. Try a 120 pilot 145 main and see what that does and go from there

Im using an open filter type.

 

[fastgtfairlane]

I'd even try a 125 pilot 150 main being that it's a chicken which is much heavier load than a standup or x2. You'll want to jet up.more to compensate. Try a big jet increase on the pilot first. Then adjust accordingly.. Hopefully you've made it too rich on the low speed circuit so that you've found the limit.. then try middle jet between what was in it and what made it go rich. Tune low circuit first then main circuit. Do it same way. I like to set the off idle transition to main circuit on a trailer backed into the water before riding it. Get it as close as possible on the trailer then go ride it.

 

[E350]

Opened my wife's SBN44 and found this:




Didn't see it on Jetmaniac's part list, so I ordered a new oem body from partzilla.com

 

[kawa js550]

Opened my wife's SBN44 and found this:

View attachment 448917


Didn't see it on Jetmaniac's part list, so I ordered a new oem body from partzilla.com

What symptoms were you having with this? Would it even run on its own fuel?

 

[E350]

It ran but it had a bog from low speed to high speed.
And it was a little hard starting which required more prime pump than usual.

 

[Storbeck]

I would listen to wfo and do all the stuff he said.

But, also.... The check valves are the thing the prevents the pump from losing prime, you suspect you damaged the check valves, and you are losing prime. Seems like I wouldn't be ruling out the check valves, it's pretty easy to pop open the carb and give them a look.

But you also need to know that all of the other stuff wfo mentioned is good, but just for this problem but for reliable operation in general. Especially take a look at the fuel pump pickup in the tank, those fall apart sometimes. I replace them with the "clunks" with a check valve that jetmaniac sells. You might find that your whole fuel pickup in the tank is a corroded mess.

 

[E350]

^^^ Do what he said.

Her symptoms would probably have been worse, but I run these check valves on the end of our rigid stainless steel fuel pick tubes in the fuel tank:

 

[JC-SuperJet]

What he said!