Help ski super lean

[Qatar2stroke]

Hey everyone I need help with my ski, 2015 superjet 701 stock head bpipe msd

Last year I was in the ocean and the ski had a failed coil, had to limp it back to shore, changed coil leads got spark and still its unrideable, and can’t figure out what’s wrong with it till now!!!

Ski runs lean in the water, I have to turn the screws all the way up to 3 turns high and low and still super lean, so I figured there is a leak somewhere???

So this is What I got done so far

-new crank seals

-new cylinder gasket

-new head gasket

-new intake and exhaust gasket

-new piston rings bearings washers snd locks ( decided to change when I opened the engine)

-All New electronics from stator to ebox

-new Yamaha fuel lines and check valve

-new gold sbn 38 carbs from highspeed

(140main-75pilot 1.5n/s and 95g springs) I went through them and clean 3 times

-checked reeds back to back from stock to vf2s no bueno

-new battery

I inspected the cylinder, cases snd the crank bearings during seal job and they seem good,

pressure tested the engine and it held 10psi for 5 min, 150/150 psi both holes,

On the hose the ski sounds crisp but forget running it in the water if not turning the screws all the way out,, I’m getting pulse, but the engine is starvinggggg

Is there anything I could be missing, im not sure what else to look for, thanks guys!

 

[orangefinger]

Just tossing at u ..

check valve installed correctly and u tested its working ?
fuel cap still has rubber O ring inside it ?
fuel selector switch checked for clogging ?
Diaphragm in correctly ?

 

[Sparkplug]

What is a gold sbn carb? Why did you buy new carbs? Why didn't they set them up for you?

This is a good example of why you dont just throw brand new parts at a ski. You possibly compounded your issue. Or even added "new" parts that are defective. Always properly diagnose issues before replacing anything.

 

[Qatar2stroke]

What is a gold sbn carb? Why did you buy new carbs? Why didn't they set them up for you?

This is a good example of why you dont just throw brand new parts at a ski. You possibly compounded your issue. Or even added "new" parts that are defective. Always properly diagnose issues before replacing anything.

non oem super bn 38s? we call them gold sbns here,
My oem 38 carbs were shot from salt, all bolts seized and would not open even after ultrasonic cleaning,
it was time for new set..

 

[fastgtfairlane]

How do you have your fuel lines plumbed? The gold sbn 38s you got will flow more fuel than the oem 38s that were on your superjet. Are you running dual fuel pumps aa well? Also what intake manifold are you running? If you're running the stock manifold, you're gonna want to plug the crossover tube that connects both cylinders. Having that crossover opened with dual fuel pumps and fuel feed will affect your tuning quite a bit. Try plugging it and see what happens. I'm suggesting this because it's what you haven't checked yet and it sounds like you replaced everything else

 

[Qatar2stroke]

How do you have your fuel lines plumbed? The gold sbn 38s you got will flow more fuel than the oem 38s that were on your superjet. Are you running dual fuel pumps aa well? Also what intake manifold are you running? If you're running the stock manifold, you're gonna want to plug the crossover tube that connects both cylinders. Having that crossover opened with dual fuel pumps and fuel feed will affect your tuning quite a bit. Try plugging it and see what happens. I'm suggesting this because it's what you haven't checked yet and it sounds like you replaced everything else

carbs run on one pump on stock intake, line coming from reserve nipple to master carb bottom nipple and out to slave carb bottom nipple and return from slave carb top nipple to tank, previous owner tapped the case for second pulse but its capped, I doubt its a carb issue but ill try to get a hold of stock 38s of a friends sj with similar setup and update

 

[fastgtfairlane]

Those carbs are not designed to run that way. I bet if you set it up with dual pumps and dual feed, and plug the crossover, your lean issue will go away. Also the front carb should be the slave carb, not the rear. Those gold 38s are similar to the oem but different and flow more fuel. Similar to the a/m sbn 44s to the oem yamaha sbn 44s.

 

[Qatar2stroke]

Those carbs are not designed to run that way. I bet if you set it up with dual pumps and dual feed, and plug the crossover, your lean issue will go away. Also the front carb should be the slave carb, not the rear. Those gold 38s are similar to the oem but different and flow more fuel. Similar to the a/m sbn 44s to the oem yamaha sbn 44s.

thanks for the input, ok so I switched to old translucent lines to see what's going on, and I have plenty of fuel coming in and when I pull the return line from carb side it shoots plenty of fuel out, also tried to add another pump to slave carb and issue still remains, I couldn't find a way to plug the crossover though, is there a chance my MSD/stator is giving me weak spark and therefore causing a lean mixture ???

 

[fastgtfairlane]

You'll have to remove the intake manifold and use some epoxy putty to fill the crossover tube in. Your issue very well may not be carb related at all. It sounds like it could be electrical related since carb changes have made no difference.

 

[JC-SuperJet]

What is the actual measured pop-off pressure on each Carb? Those A/M Mikuni SBNs normally come with 115gr Springs. HSI could have forgotten to swap or installed wrong Spring?

You could insert a Jet (try a #60) in the Return Line to raise the Fuel Pressure going into the Carbs so that the Needle Valve pops and allows more fuel to go into the Carb Throat. Or even just pinch/squeeze/choke the Return Line down with a zip tie for a quick temporary test.

Are the Throttle Plates synchronized? Do they bofth open fully when the Throttle Wheel is turned?

Is the Supply Line Fuel Filter new, clean and not clogged? Beware of SIntered Bronze filters.

And just in case, cap the Primer Nipple on each Carb if there is no Primer System. Keeps the Air Flow into the Carb Throats straighter and stronger.

Note that the Fuel Tank Check Valve arrow must point towards the Tank as it allows air in to break the Tank vacuum which will starve a Carburetor.

 

[Qatar2stroke]

What is the actual measured pop-off pressure on each Carb? Those A/M Mikuni SBNs normally come with 115gr Springs. HSI could have forgotten to swap or installed wrong Spring?

You could insert a Jet (try a #60) in the Return Line to raise the Fuel Pressure going into the Carbs so that the Needle Valve pops and allows more fuel to go into the Carb Throat. Or even just pinch/squeeze/choke the Return Line down with a zip tie for a quick temporary test.

Are the Throttle Plates synchronized? Do they bofth open fully when the Throttle Wheel is turned?

Is the Supply Line Fuel Filter new, clean and not clogged? Beware of SIntered Bronze filters.

And just in case, cap the Primer Nipple on each Carb if there is no Primer System. Keeps the Air Flow into the Carb Throats straighter and stronger.

Note that the Fuel Tank Check Valve arrow must point towards the Tank as it allows air in to break the Tank vacuum which will starve a Carburetor.

View attachment 440492View attachment 440493

Thanks for the input, ok so I had some time to wrench on the ski, carbs got the dull silver springs, I made a diy pop of tester and both carbs are measuring low 40s ( not accurate ) tried OEM 38s off a friend ski and issue still remains, double check all line I have pressure in gas tank

Pinched return line Also switched to known good cdi/stator with no results,

Engine is very very lean no matter what I do

I’m getting desperate here

Could I have overheated the engine at one point and cause internal damage that I could not spot?

I did refresh the engine and inspected everything briefly, but maybe I have missed something that could cause me a lean condition..

 

[JC-SuperJet]

Maybe one of the Pulse Fittings or Pulse Hose is leaking. Repeat the Air Leak-down Test. Connect the Test Line to the original OEM Pulse Fitting/Hose.

You mentioned that the Original Carbs were severely corroded. Maybe the Exhaust Manifold, Head Pipe or Chamber have pin holes. Is the Exhaust Silicone Coupler split or torn?

Also inspect the Aluminum Waterbox for corrosion and pinholes.

Run the submerged Ski on the Trailer WITH the Hood latched down tight, Run for a minute feathering to full throttle, then remove the Hood to see if the Engine Bay is full of smoke.

And check, with the Hood removed and the Engine running, that Water isn't leaking into the Hull via the Midshaft and splashing Water into the Flame Arrestors/Carbs.

For reference, this is what Lean and Rich Piston Tops look like:

 

[Qatar2stroke]

Maybe one of the Pulse Fittings or Pulse Hose is leaking. Repeat the Air Leak-down Test. Connect the Test Line to the original OEM Pulse Fitting/Hose.

You mentioned that the Original Carbs were severely corroded. Maybe the Exhaust Manifold, Head Pipe or Chamber have pin holes. Is the Exhaust Silicone Coupler split or torn?

Also inspect the Aluminum Waterbox for corrosion and pinholes.

Run the submerged Ski on the Trailer WITH the Hood latched down tight, Run for a minute feathering to full throttle, then remove the Hood to see if the Engine Bay is full of smoke.

And check, with the Hood removed and the Engine running, that Water isn't leaking into the Hull via the Midshaft and splashing Water into the Flame Arrestors/Carbs.

I did pressure test the engine yesterday from both pulse lines with front cover off, passes test, as well as 150 on both holes

Last test on the water I did check for any signs of smoke, negative,

All couplings are ok and tight

I checked the waterbox for any sound inside and exhaust pinholes everything looks visually good, I even ran stock exhaust to eliminate any underlying issues,

This has been going on for months now and I made sure everything is leak free and tight, carbs and electricity went through multiple times back to back with other working components

A friend is saying a twisted crank/bearing could cause something like this? I don’t want to split the cases again but I think I have to atp

 

[Qatar2stroke]

This is prior to refreshing the engine

 

[JC-SuperJet]

Did you find and fix the issue?

What was the Root Cause?

 

[Qatar2stroke]

Did you find and fix the issue?

What was the Root Cause?

Hi thanks for asking I have been busy out of town, didn’t have a chance to follow up yet,

last test in the water engine and water from pissers were really hot, I’m not sure it’s hot because it’s lean or it’s lean because it’s running hot, also loads of carbon build up around spark plugs but electrodes are dry

On the hose it’s very cool,

I am hoping I don’t have to take eveything apart as soon as I come back I will check manifold and head pipe and all water routing from pump to overboard and see how it goes from there

Will update once back..