Running like crap now, but all of a sudden and don't know why.

[Zero Client]

Posting this for a friend, who has the following ski:

Its a 62t cases with 62t cyl which was just rebuilt 5 hours ago.
Carbs are dual aftermarket 44mm Mikunis.
R&D Intake.
B-Pipe
ADA-Girdled Head
Stock CDI
Dual fuel feed dual filters
Aftermarket FAs
Jetting specs were running absolutely perfect before performance degraded


Tuning was done and carbs were originally clean.

The story goes like this. Engine was running great all day. Then he went back to his ski and tried to take off from the beach stand. The ski stumbled and sputtered with little to no throttle response. Back on the beach stand, the ski ran like crap while we were troubleshooting, and finally we noticed both diaphragms of the 44mm carbs were leaking.

The ski feels like its very restricted and weak and wants to die/stall while running.

Things I've tried helping with tried:
1. We rebuild the the carbs two different ways: First all the seals and gaskets, then re replaced the butterflies and mechanisms to new spec. The carb is now clean with new parts everywhere and very tight. Carbs are running dual pumps with feed lines from the top/inside of each reed cage. No changes after this.
2. The reeds look a little bit worn, with one of them slightly open maybe 2~3mm. Local gurus say the reeds are likely still OK and not causing the problem. Reeds are questionable but research shows these may not be a problem.
3. Tank was drained and cleaned. New filters. New gas. Premixing Pensoil. Tank vent OK. Carbs cleaned and checked again as well. No change
4. E-Box opened for inspection. Fuse replaced. CDI replaced. Coil replaced. No change at all.
5. Compression is great. Still 195psi per jug. Engine should be healthy with recent professional rebuild.
6. Checked woodruff key/flywheel and was normal. Timing is set just slightly advanced
7. No real good way to check the stator. Hey, it starts, and the battery charges - it just runs like a POS.
8. Waterbox flows free as in no blockage. Same with exhaust back from W/B to tail end.
9. E-Box temperature sensor removed and disconnected - wires left disconnected inside eBox.
10. New plugs.
11. Fuel pickups checked and pressure tested
12. Tested grounds into eBox at 0.5 ohms meaning good connection. Tried a second ground just in case.

Any other ideas? Could it be a stator or anything?

 

[Quinc]

Are both plugs getting spark? It sounds like it is only firing on one plug.

 

[550/440]

I did a ton of work like that once only to find it was a bad plug... but you've checked and replaced those.
Have you blown all the fuel lines clear to ensure no blockage and no leaks / cracks?

 

[Zero Client]

Plugs have been changed out. All the fuel lines are transparent and - not only have been blown out but show to be pumping fuel when limp/running.

We'll try pulling one plug boot at a time to see how the engine runs/if on one cyl at a time.

 

[x2Ufoolz]

I have pulled both plugs and they are both arching to the head

 

[blaster800]

QUOTE : ''The ski feels like its very restricted and weak and wants to die/stall while running. ''' when my stator and flywheel met after the bendix went bad it acted just like this , the stator was forced into a RETARDED timing position , just FYI .

 

[Zero Client]

The timing hasn't moved it's still 1/10 inch advanced. That's not to say it might be a bad stator but clueless really.

 

[SJ Thumpa]

Guessing the carbs are sinchronised and the joiner not loose?

 

[OCD Solutions]

I'd also check to see if it's load related with something going wrong with the pump or midshaft bearing possibly. Something stuck in the impeller.

 

[KTM434]

Don't rule out the reeds. Open 2-3mm means they're junk anyways. If you didn't want to buy new ones at least flip them for testing purposes

 

[tor*p*do]

replaced the needle and seats?

 

[x2Ufoolz]

We replaced an oring on the girdled head, it looked kinda pinched but not broken, put a very clean perfect running stator and flywheel from another ski, ran it straight piped to make sure it was water box, unhooked start stop switch, checked pump bearings with plugs out fine, tried to mess with carb settings more. The carbs have been rebuilt with new parts twice with perfect sync and new butterfly's. Nothing has changed at all.

Could it be the cylinder base gasket??

 

[Quinc]

If it is the base gasket a leak down test should show it. Or start her up and spray some ether down and around it to see if it takes off. Another thing you might check is the spark plug tester on the actual plugs to make sure they are getting spark while she is running. There might be a bad spot in the plug wire where it is grounding before it makes it to the plug. I also had an issue where it would spark great for 10-15 seconds and then stop.

 

[XJCrawler]

Does it try to run away when not under load?

Have you confirmed your get a strong spark from each plug?

Did you check pop off after the rebuild? Might be a leaking needle and seat

 

[x2Ufoolz]

it was trying to run away and then it stopped doing it, I just took the ski on a surf trip with a different motor and it ran perfect so that rules out start stop switch, pump, tank, waterbox

 

[x2Ufoolz]

I took it to the lake 4 times last week trying to get it going. The low and high screws make no difference whatsoever. It boggs and then takes off wide open and rips, let off the gas starts boging for like 5 seconds and then rips.

I also switched the stator and flywheel out of the motor I just rode in the surf that ran perfect, so that rules out anything electrical

 

[x2Ufoolz]

I took my bpipe off to put a stock motor in and the manifold was soaking wet. I guess I need to take the jugs off because thats the only thing I havent checked. And/or do a pressure test on it

 

[550/440]

If it tried to run away, you might have a pulse signal issue - the pressure test is a good idea.

 

[Big Kahuna]

Check your plug wires for breaks, also check the wiring harness where the wires go through the electrical box. Had this happen before where the wires were broken and caused the ski to run like yours.