Air leak from hell!

[Quinc]

Been trying to tune this damn ski all season and some days it runs great all day other days it has an air leak. Hoping to get some ideas before I rebuild the damn thing again.. This is what I have done so far if anyone has any other suggestions or things to check it would be much appreciated.

-Engine is completely rebuilt with JM gaskets and oem seals last year with 1211.
-Rebuilt carbs
-cleaned and checked pop-off way too many times
-Leaked tested to 14 psi cold 30min
-Leaked tested to 14 psi on a 95 degree day with the engine in the sun 30 min spraying soapy water all over the crank seals and everywhere else including front crank seal
-replaced fuel line inside fuel tank
-replaced fuel line to carbs
-greased orings on boyesen intake
-new gaskets and 1211 under carbs
-confirmed you can move pole up down and side to side without effects throttle cable
-New stator, different CDIS and msd, 2x ground wires, freshly charged new battery, OCD coil, new plugs, cleaned and di-electric grease all connections.

 

[erik mx45]

electrical issue possible ? check plug caps connection

 

[DAG]

When you leakdown are you testing the intake manifold by sealing off at the carb mounting surface?

 

[DAG]

Also what are your symptoms? You say it has a airleak, what is the ski doing?

 

[Quinc]

electrical issue possible ? check plug caps connection

Brand new OCD coil and plug wires, OCD refurbished stator and also tried a stator out of a waveraider. I did have issues with an EPIC and switched it out for a known working enhancer. I will probably try oem cdi next.

Also running two grounds and a ground from the battery directly to the ebox.

When you leakdown are you testing the intake manifold by sealing off at the carb mounting surface?

Freeze plugs in the manifolds.

Also what are your symptoms? You say it has a airleak, what is the ski doing?

Ski idles fine and I can blip it to 1/4 throttle or so on the trailer, but a blip to 1/2+ and she takes off like a rocket and I have to give full throttle and hold down the stop switch. While riding when the pump leaves the water she revs high till the pump is back in the water.

 

[Quinc]

Maybe instead of an air leak could it be that it is not getting enough fuel? Grasping at straws at this point..

 

[Quinc]

As another test I removed the inline fuel filters and ran clear fuel line. Some tiny air bubbles in the line but not much. Symptoms stayed the same. Fuel lines are also as short as possible and zip tied.

 

[Ducky]

I had similar issues, and it was because my carb coupler loosened up and the carbs were out of sync.

 

[Quinc]

I had similar issues, and it was because my carb coupler loosened up and the carbs were out of sync.

I also had that issue last month. I checked them again last night to make sure and they are good.

I have a set of BJ'S I can toss on to rule out the carbs.

Current are mikuni 44s
125 pilot
120 low
27psi

Any ideas for jetting the 48 bjs? Or stay with the same jetting as the 44s?

 

[kswiatk]

My most recent air leak was my throttle shaft seal leaking. also maybe open your lower screw up some more?

 

[Quinc]

I think I found it!

Ran the ski on the trailer tell the head was 140F then ran just enough water through her to keep the temp at 140 and sprayed carb cleaner all around. Spraying under the intake manifold she will die. So going to pull the engine and put a new gasket and a poop ton of 1211 on her and put her back together... Also going to try doing a leak test with vacuum vs pressure to see if she leaks one way vs the other. Anyone know how much you can vacuum test up to? -10psi or -14psi etc?

 

[Tyler Zane]

I dont go over 10lbs and a vacuum test isn't necessary.

 

[Harbor]

Might as well check the carb and intake flanges for flatness while it's apart, if not done already. The R&D I had was warped up at the carb mounting studs, carb would not sit flush and rocked sideways.....migt richen idle screw if needed.

 

[Harbor]

On the vacuum test I'd go 18 to 20 inches

 

[Quinc]

Might as well check the carb and intake flanges for flatness while it's apart, if not done already. The R&D I had was warped up at the carb mounting studs, carb would not sit flush and rocked sideways.....migt richen idle screw if needed.

Boyesen intake I bought new last season so hopefully she is not warped.

A couple weeks ago I road at 5600ft and she ran awesome. Suppose the colder water kept the engine cooler and less air meant she had more fuel so the perfect combo not to have an air leak..

 

[Harbor]

Ya that manifold you have is way newer, the R&D I had was well used lol....

So the elevation change cured the issue for a bit so you've either got a leak from hell like your thinking or the base mixture is too lean..

Have you already tried opening up the lows 1/4 or 1/2 ?

 

[Quinc]

Ya that manifold you have is way newer, the R&D I had was well used lol....

So the elevation change cured the issue for a bit so you've either got a leak from hell like your thinking or the base mixture is too lean..

Have you already tried opening up the lows 1/4 or 1/2 ?

I went up a full jet size on the lows and no difference from 1/2 turn to 2 turns. Also lowered pop off. Going to do a new gasket and need to figure out a way to leak down the engine at 130F+. Maybe in the hot sun with a heat gun blowing on it?

 

[DAG]

Your test should have found the leak if there was one. I’ve herd of pin holes in the casting creating sporadic lean conditions. Is the runaway sporadic or can you pretty much guarantee it will happen if you open more than 1/4? Have you pulled the head to look at piston wash? How long has this been happening? If you suspect the air leak is happening all the time you should have lean washed pistons.


Do you have another set of carbs you could try. Maybe swap with a friend for a day to help rule out the carb.

 

[Harbor]

I went up a full jet size on the lows and no difference from 1/2 turn to 2 turns. Also lowered pop off. Going to do a new gasket and need to figure out a way to leak down the engine at 130F+. Maybe in the hot sun with a heat gun blowing on it?

Ok, Sound like went thru that well enough....

What about removing your stator and carbs and set up for pressure test and put the engine in the oven @ the desired temp and let it heat soak until evenly warm then presure test it ?

I guess the heat gun would be less work but not exactly the same in terms of even heating

My 49's I ran on my 865 were 135h 125L 2.3 seat 115 spring

No issues with your throttle shafts being worn or the the butterflies worn away at the shaft in the corners ?

 

[DAG]

OMG dont put the motor in the oven... If you want to heat it up why not pull the motor. Bolt it to a piece of wood. Run it on the hose and restrict water (at the pisser) to change operating temp.

Does the motor not run away when you first start it up on the trailer cold?