1995 750 SLT Snorkel intake modification and triple output fuel pump install

[WaveChaser]

This has been a two year project as I have not had a lot of time to mess with this ski. This ski when I purchased it had the single outlet fuel pump and snorkel intake. I purchased the modern type flame arrestor and oilers plate. It said in the instructions to increase the the main jets in the carburetor and I did that.

I see gas dripping in the one of the carbs so I performed a pop off and it was ok. It will run and rev on trailer but bog in the water.

The one thing I cannot find is how to set the carburetors. These are the factory setting:
750 - Low Speed – 1/2
High Speed – 1m, 1/2c, 3/4p

I am thinking it has to be more set to my 1997 780slt with the triple pump and modern spark arrestor.

There use to be a pdf of all the factory settings for all the polaris models but I cannot find it now.

Does anybody know what the correct carb settings should be after this mod?

Here is the link I followed.

https://www.shopsbt.com/forum/showthread.php?t=23527

[WaveChaser]

Wow. Nobody?

[BlueFishCrisis]

This has been a two year project as I have not had a lot of time to mess with this ski. This ski when I purchased it had the single outlet fuel pump and snorkel intake. I purchased the modern type flame arrestor and oilers plate. It said in the instructions to increase the the main jets in the carburetor and I did that.

I see gas dripping in the one of the carbs so I performed a pop off and it was ok. It will run and rev on trailer but bog in the water.

The one thing I cannot find is how to set the carburetors. These are the factory setting:
750 - Low Speed – 1/2
High Speed – 1m, 1/2c, 3/4p

I am thinking it has to be more set to my 1997 780slt with the triple pump and modern spark arrestor.

There use to be a pdf of all the factory settings for all the polaris models but I cannot find it now.

Does anybody know what the correct carb settings should be after this mod?

Here is the link I followed.

https://www.shopsbt.com/forum/showthread.php?t=23527

The kit came with larger jet sizes, and didn't suggest alternate needle settings after install.. What size jets did you install? There is never a magic carb setting, just a starting point. You need to tune manually from there.

[RLACEMAN]

Set the mixture screws to the 1996 SLT setting. The 97 had them set all the same, but used different size jets in each carb, those did run a bit better cause they were easier to tune.

[WaveChaser]

The jets are 102.5 mains as it only said to replace them. From what I read you start at the "stock settings" and then turn out 1/4 turn, run and check the plugs to see if they are chocolate brown and wet.
I rebuilt the carbs including seats and float valve. the pop off pressure is around 18-20lbs. I replaced the mylar flap as well but I see fuel dripping down the throat of one carb. I have taken apart the carbs 3 times now and everything looks fine and in place. To me either with the new larger mains, I need to turn down the lows or something is not right in the carbs.

Here are the stock settings:
750 - Low Speed – 1/2
High Speed – 1m, 1/2c, 3/4p

If these are not correct settings? What should be my base settings?

[WaveChaser]

I am getting nowhere with this ski. I have gone through the fuel system and totally rebuilt everything:

rebuilt carbs
installed and rebuilt tripple output fuel pump
installed new gas valve
tested popoff pressure at 18lbs
Installed 102.5 main jets in all 3 carbs per airbox modification
Installed 1997 airbox modification.
new rings.
New plugs.

Here is the issue.
Set Low Speed – 1/2
set High Speed - 2

Idle machine on hose, pull plugs. Plugs are wet and sloppy.

Put ski in water and ride around up to 1/2 throttle for a minute or two. Check plugs and plugs are white and dry.
Start ski back up, let idle 30 sec, pull plugs, wet and sloppy again. It is obvious that it is starving for gas. I have clear gas line and there are no air bubbles in the line.

I have read on the net where guys do the airbox mod and just open their jets more. I have changed the pump from a single output to a tripple and increased the main jet to 102.5. Do I need to increase the high jet as well? This should not be this difficult.

[RLACEMAN]

You need to ride around 15 to 30 minutes to get color on the plugs. So what exactly is the issue, its bogging on take off? You need to determine if its a lean or rich condition, if its bogging on take off & you pull out the choke a bit & it takes off its lean if it falls on its face then its rich. When you figure out which it is then procede from there. With the setting you have listed I think the low speed should be out at least 3/4 to 1 turn & the high speed should be no more than 1 1/2. Usually when changing over to this airbox the pilot jets should also be one size larger. I had a low speed bog in mine & the only way to get rid of it was larger pilot jets. Also I ask everyone with this type of problem what type of fuel are you using?

[WaveChaser]

With all three plugs running an aluminum color and dry just riding the ski around for a minute or two, it is running super lean and I am going to burn up the top end. This thing is starving for gas but I don't know where. I figure with the Hi out 2 turns, the plugs should be super wet or at least damp. They are dry as a bone. Only when I idle it for 30 seconds do they become wet again.

[xplayer2885]

I know this is an older thread, but have you performed a crankcase leak down test? Only asking because when I had my 750 the symptoms you are describing are similar to what I was experiencing. In my opinion I would also remove the Stator cover and check for oil buildup. This is a sure sign the front crank seal is leaking.

hope this helps

[WaveChaser]

I still have not figured this ski out. One thing I noticed was the water separator was not filling full so I cleaned and replaced the Oring. I took the separator, plugged the out and tested it in a buck of water with air. It did not leak at all so I figure that is fixed. I have also installed new fuel lines again. I bought a new triple Mikuni pump. Now the ski at idle to 3k rpm, the Mag seems to be nice and wet but the Center and PTO are dry. The ski doesn't bog it takes off nicely but running the C and P lean, I can feel the difference on the plugs when I take them out to test. The M is warm but the C and P are hot and I find them dry. One thing I notice when I goose the throttle with the seat off, I see the water separator level dipping and sucking air once again. I even looked at and tested the vent valves and they seem to be passing air correctly. There is no logic to this machine and there is nothing obvious.

So Xplayer2885, i don't think I have a vacuum leak with what happens to the separator level and sucking air once more. I have taken the fuel system apart from tank to carbs. Until I get this water separator to stay full and not suck air, this thing will never run and adjust correctly.

[xlint89]

What fuel hose are you using?

[sdlvx]

I still have not figured this ski out. One thing I noticed was the water separator was not filling full so I cleaned and replaced the Oring. I took the separator, plugged the out and tested it in a buck of water with air. It did not leak at all so I figure that is fixed. I have also installed new fuel lines again. I bought a new triple Mikuni pump. Now the ski at idle to 3k rpm, the Mag seems to be nice and wet but the Center and PTO are dry. The ski doesn't bog it takes off nicely but running the C and P lean, I can feel the difference on the plugs when I take them out to test. The M is warm but the C and P are hot and I find them dry. One thing I notice when I goose the throttle with the seat off, I see the water separator level dipping and sucking air once again. I even looked at and tested the vent valves and they seem to be passing air correctly. There is no logic to this machine and there is nothing obvious.

So Xplayer2885, i don't think I have a vacuum leak with what happens to the separator level and sucking air once more. I have taken the fuel system apart from tank to carbs. Until I get this water separator to stay full and not suck air, this thing will never run and adjust correctly.

I had a similar problem to you at one point and it's because there was a small hairline crack in the fuel selector spigots. Mine were plastic so I don't if yours are metal, but if they are plastic it could be that. All it takes is one little leak somewhere, something not tight even, and it can be a problem.

[WaveChaser]

I started out with clear. It is pretty stiff and you cannot pinch it shut with your hand. So then I purchased some really stiff fuel line that is rubber inside and nylon outside. I have changed to that and no change.

Here is the weird thing. I bought a 20 gal/hour electric pump. I test by disconnecting the triple input and connecting the input house to the electric. I then connect the electric pump to the battery and pump the gas into a can. That is were I saw the separator and fuel switch leaking. I no longer see air bubbles with the electric pump. According to specs, 20 gal/hr is twice that of the triple pump of only 35L/hr or 9.2 gal/hr. I thought I had the air problem solved because the separator fills nicely and no airbubbles in the lines. However as soon as I connect the triple pump and test on the trailer, I see the separator level draw down when I goose the throttle and get air bubbles once more. I have replaced everything in the fuel system up to the carbs.

The 1995 does not have hoses in the tank. It has an all aluminum stack with the fuel gauge receiver. Maybe when the engine is running, the vibration is causing some component to leak air into the system. I agree that it is some small crack leaking. I thought it might be the separator bowl. Thats why I plugged the out and filled with air under water to test for leaks and nothing. I have also had the fuel stack out of the tank and tested it for leaks as well. Everything seems fine.

Even though the fuel switch is brand new and plastic, I will bypass it because it is before the separator.

[K447]

It is possible for the fuel supply nipple on top of the fuel sender to not be 100% air tight to the vertical aluminum tube inside the sender. The fuel fittings are just press fit into the aluminum extrusion.

Air leaks there will flow air bubbles into the separator.




The separator lid has an o-ring, which must seal 100%.
There is also a much smaller o-ring inside the top of the metal filter canister, if your separator has the inside.

http://greenhulk.net/forums/showthread.php?t=206730&p=2263984&viewfull=1#post2263984

[casey67]

When the fuel burns, its temp is like 3,000 deg F.
The spark plugs should not be cool.
The spark plugs job is to burn ALL the gas, so being tan and dry is correct.
The plug shouldnt be wet, unless when the engine is stopping, it draws fuel and doesnt burn the gas.

For tuning its best to use plugs that have a couple hours on them. The color will change in a couple seconds depending on mixture ( literally 2-3 seconds)
If it does not bog on take off, the mixture will be pretty close. Lean will cause bog. Too rich will cause a missfire, referred to as "girgle".
Plug color + piston wash will tell if mixture is correct.

As far as seperator, I would install a pressure gauge, before the restrictor, if pressure stays good it's fine.