Gas not getting to carb

[JoeJoey]

My son and I are new to this. We ended up with a 1993 Sea doo sp with trailer pretty much for free. It's been sitting for probably 10 years. It's definitely not the stock engine nor is it stock carb and ignition. We got a battery, replaced fuel lines...drained gas and put in 4 gal of premix to the tank. It cranks and even runs if you prime it. But there is no gas getting to carb. We can suck the gas from the line going to carb so it's not clogged. My question is what provides the gas? Is it the carb providing suction or something else?

 

[POPPS]

If it doesn't have an external fuel pump since you said that it appears modified, the fuel pump side of the carb gets its pulse (vacuum), from the motor through a line from the motor to the carb at the front of the motor. Connect the out line of the fuel pickup directly to the carb. This bypasses the fuel selector that can plug up over time. The carb also has an internal micro filter that can get plugged over time. If you have the gray fuel lines, they break down internally and eventually plug orifices in the carb, along with that micro filter. I also like to blow gently (open your gas cap),into the on and reserve inlets on the fuel pickup to clear any debris on the screen at the bottom of the fuel pickup.

 

[Joey White]

I'm working on this jet ski as well. Just a different account. You said that there is a vacuum created by the motor. I Believe I know which line you are talking about. But when I turn it over the line does not create a vacuum but instead blows air out. I'm not sure if that's suppose to happen or not. Also with both of the carburetors (it is a dual carbonated motor) I can not blow into the intake for the gas. I'm not sure if I'm suppose to be able to do that but from what I've looked at inside the carburetors it seems to be clean and not clogged at all.

 

[NickCawks]

That is correct. The pulse line creates pulses of pressure not vacuum.

Have you tried pressurizing the gas tank? You would do this by putting a compressor nozzle to the 1 way valve that functions as a vent for the gas tank. You will find this on the outside of the ski just under the trim. There is one for the oil tank and one for the gas tank, make sure your doing this to the gas tank

When I first rebuilt my xp it would not start until I did this

 

[JoeJoey]

We tried that to no avail. Good suggestions though. Despite seeing anything obvious when we took the carb apart I'm going to take it off again and take it to the local jet ski service shop. I'm suspicious of it and that the fuel pump part isn't working as it's not pulling fuel.it's got 4 gal in the tank so that's not an issue and it primes fine.

 

[JoeJoey]

A rebuild kit is $48 for this thing and I'd hate to sink that money and time into it not knowing for sure that it's the problem

 

[NickCawks]

99% of fueling issues are carb related. As you said the ski has been sitting for 10 years it's probably time for a carb rebuild regardless.

 

[JoeJoey]

I'm leaning that way too, and I think I'm going to go ahead and sink $ into it and hope that takes care of it. As you said..it needs it anyway

 

[POPPS]

My son and I are new to this. We ended up with a 1993 Sea doo sp with trailer pretty much for free. It's been sitting for probably 10 years. It's definitely not the stock engine nor is it stock carb and ignition. We got a battery, replaced fuel lines...drained gas and put in 4 gal of premix to the tank. It cranks and even runs if you prime it. But there is no gas getting to carb. We can suck the gas from the line going to carb so it's not clogged. My question is what provides the gas? Is it the carb providing suction or something else?

You can't suck gas from the carb, there is the clear pulse diaphram, that pulls fuel in from your tank, and then 2 circular clear check valves, next to the pulse diaphram that work opposite to each other and draw the fuel in to the carbs.

 

[Joey White]

You can't suck gas from the carb, there is the clear pulse diaphram, that pulls fuel in from your tank, and then 2 circular clear check valves, next to the pulse diaphram that work opposite to each other and draw the fuel in to the carbs.

He meant to say from the gas tank. I can't suck or blow into the carburetor.

 

[JoeJoey]

Update on this. Rebuild kit came in. Rebuilt carb. Took a while to get fuel to come through the line but we did. Then we primed it and it fired up. It won't run for long before it dies, but definately running longer than the fuel we prime with. It was kind of late last night so we put it back in the garage and are going to look a the low and high screws and set them at their defaults and fire it up and see what it does. We did verify the pulse is coming from the engine when we crank. We have not checked the compression in the cylinders. It's definately getting compression and running. Likely it's OK and despite it sitting for a while looks like a barely used engine. So we will update later and if anyone has any suggestions before we go at it again let me know. thanks all!!

 

[mikidymac]

Fuel strainer and fuel selector are possibly sucking air and pretty common.

 

[JoeJoey]

Yeah it's just not sucking enough fuel after doing everything. We are going to temporarily take out the fuel filter. Can't find any air getting in...when we suck on the line at the carb that goes back to the gas tank it comes through fine with no air

 

[JoeJoey]

OK. We got it running where it's sucking the gas fine. It runs like crap on idle. We may need to mess with the low mix screw some more. Giving it throttle it revs well and sounds good. It doesn't leak water other than 1 exhaust bolt we need to tighten that drips a little. We are going to take it to the lake in the morning and see what it can do. Not bad for basically a free jet ski and trailer that we spent $180 on to get on the lake.
We are at 40-1 gas/oil mix and are bypassing the oil injection and have that disconnected. We decided that was just a bad idea to use the injection on an old jet ski like this. It smokes quite a bit running in the driveway testing it so maybe it's too rich with the oil. Maybe that's because it's idling with the rich mix. Either way at this point we are just happy it runs.
Details are 1993 sea doo SP, but it has a 657cc engine 2 mikuni bn44 carbs. From what I saw they only offered the SP that year with a 587cc. Ours has some kind of aftermarket electronic ignition and aftermarket valve cover and pulse plate. It's actually pretty cool looking as far as the engine goes. The cosmetic part of the jet ski is pretty worn and rough, but nothing structurally wrong. Should be fun!!!

 

[mikidymac]

The oil injection on these are absolutely reliable.

Also you have to keep supplying oil to the rotary gear on these even if you go premix.

 

[Joey White]

It is set up to still give oil to the rotary gear. The person who had this before us did all of that and we wanted to go premix anyways because we want to make sure the ski is getting oil.

 

[Joey White]

Took it out to the lake today. It runs terrible because the carburetor needs a big tune, but besides that the jet ski works. Any tips on how to tune it? I would like to tune it out of water. But I can hook up water to it.

 

[mikidymac]

There’s no tune on these.
Basically if it’s a stock ski it will run perfectly on the stock settings. If it doesn’t you have something wrong. Carbs should only be rebuilt with genuine mikuni parts.

 

[Joey White]

The carburetors are not stock nor is the engine. The adjustment screws for high and low have been messed with. So I do need to adjust them. The Carburetors are Mikuni BN-44 without a choke. And the Engine is a 657

 

[NickCawks]

You will find the stock carb settings on this chart. Although if it is not the motor and carbs that came in it, it might not help all that much. Sea Doo PWC Carburetor Reference

 

[mikidymac]

I’m going to move this to the performance section for you.

 

[JoeJoey]

I am having trouble with my compression tester, but thinking it might be worth testing compression to see if it's within range. Looks like it should be about 140-150..is that correct? As bad as this thing runs I feel like there has to be something else besides the carb settings, but maybe I'm wrong.

 

[mikidymac]

On a stock engine with a stock head the perfect compression should be 150 psi, at 120 you need to rebuild or if there is more than about 5 psi difference between cylinders.

 

[Joey White]

I had adjusted the carburetors to the settings in the User Manual for the carburetor screws (Low 1 High 1.5). I’m messing around with the low screw first. And at 1 turn out it can flood the engine so I turned it down to only 3/4 because I know the screw is very sensitive. But the engine was getting way to much gas. I’ll try starting it like that later and see how that works and base more adjustments to that.

 

[mikidymac]

Maybe @Matt Braley has some settings in his notebook that will get you close.
He will need all the info like head, carbs, pipe, engine size, porting and possibly impeller to be able to help.