Someone please help, running out of ideas

[Jhucke]

I held off as long as I could making a thread like this but I'm quite literally running out of ideas for my issue.

My superjet is 61x/61x pretty much all stock. Jetting is what it has been at for the last three years running great 135 main, 115 low, 30 psi pop off single 44. THe motor runs like a top until consistent full throttle which results in the motor losing almost all its RPMs or dies completely. The more I ride, the worse it gets.

Initially I thought it was lean for some reason but without touching the jetting or screws or anything on the ski for that matter. FIgured it was the carbs time, rebuilt it with fresh everything including needle and seat (all genuine mikuni). None of this matters anyway because the issue still happens with a different carb (found out today).

Things I've checked and/or replaced via tearing down a running ski as a parts boat:

CDI
Stator
voltage regulator
coil
cleaned s/s connections which werent dirty in the first place
rebuilt carb with new needle and seat and later tested a completely different carb
Lines are 100% clear direct to carb by the way, no fuel selector
Filters are 100% clear
Check valve
Rear crank seal (long/different story)
New gas after draining tank
compression is 150/150
cleaned ground connections
Fuel tank straws
Exhaust leaks


Things I need to try:
Possible flywheel malfunction
Completely replace the SS switch with a known working one
Adding another ground direct to battery from Ebox post
cleaning up connections again in the ebox
Broken waterbox baffle?????
Leak down test??? But why does it run flawlessly until ive been full throttle for awhile and at inconsistent times?

Other that this I have no idea what to do. Please note that the issue is not consistent. It only does it when the boat is warm or has been running for awhile which is why I immediately thought it was electrical based. I'm not talking hours of run time, but sometimes its 30 seconds of full throttle, sometimes 4 seconds, etc but gets worse with more ride time. When it loses RPMs but doesnt die, the motor sounds really dirty and bubbly then clears up. Does not always die from the same amount of sustained full throttle. It sounds exactly like an exhaust leak, but I've had those before and my engine bay is clean as a whistle. Anyone else have any input?

 

[Jetfiend]

Are you running the fuel selector switch?

 

[Jhucke]

Are you running the fuel selector switch?

Nope, straight to the carb from the reserve line.

 

[Jetfiend]

Nope, straight to the carb from the return line.

My mistake, I just read your original post again..

There goes that theory.. I would swap out that S/S and run a new ground next. I know it's frustrating man, I just went through this to find out that the fuel switch was choking fuel to the carbs. Hang in there and just keep eliminating things.

Edit: also check your gas cap for cracks and that the seal is good.

 

[Davidomilligan]

You check your reeds?

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[Jhucke]

My mistake, I just read your original post again..

There goes that theory.. I would swap out that S/S and run a new ground next. I know it's frustrating man, I just went through this to find out that the fuel switch was choking fuel to the carbs. Hang in there and just keep eliminating things.

Edit: also check your gas cap for cracks and that the seal is good.

Thanks for tryin, lol. I will do those things.

 

[Jhucke]

You check your reeds?

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Nope. People are telling me on Facebook to check reeds and cages, too.

 

[Davidomilligan]

Nope. People are telling me on Facebook to check reeds and cages, too.

Ya make sure they are flush on the cages and you can't see light through them

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[Jhucke]

Ya make sure they are flush on the cages and you can't see light through them

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I pulled them. They are boyesen two stage reeds. I could definitely see light through more than one of them, I'm suspecting that they are worn. I replaced them with some stockers for tomorrow. I also ground all the earth wires down to bare metal, ran an extra earth to my ebox, rigged in a known working s/s switch through the bilge pump hole (seriously?). Flywheel on the bench ready to go to be swapped in if I need to. Hoping that the water is smooth tomorrow I can ride with the hood off to see if I have any weird poop happening.

 

[Pro-pulsion]

Sounds like the coil to me. I know you mentioned you have tested it but when they get to the end of their life span they can breakdown when under varying load ranges. Some will heat up and breakdown, some will fail under higher RPMs due to the copper windings being deteriorated just enough to not conduct fully. This can also be seen with the high tension leads typically at the boots. This is why a lot of people will trim the leads back about 1/4 of an inch. If it is a stock coil then I would think it is safe to assume it is due for replacement. I was talking to a couple of friends the other day about this very thing. The one guy said he has had to swap out the OEM coil with either a JetManiac or OCD coil on all 4 of his Blasters. One of which was running the 61x/61x single carb 701 motor.

Edit: I misread the things your have checked/replaced. I missed the "replaced" part. Did you swap out the coil or just test it?

 

[Jhucke]

Sounds like the coil to me. I know you mentioned you have tested it but when they get to the end of their life span they can breakdown when under varying load ranges. Some will heat up and breakdown, some will fail under higher RPMs due to the copper windings being deteriorated just enough to not conduct fully. This can also be seen with the high tension leads typically at the boots. This is why a lot of people will trim the leads back about 1/4 of an inch. If it is a stock coil then I would think it is safe to assume it is due for replacement. I was talking to a couple of friends the other day about this very thing. The one guy said he has had to swap out the OEM coil with either a JetManiac or OCD coil on all 4 of his Blasters. One of which was running the 61x/61x single carb 701 motor.

Edit: I misread the things your have checked/replaced. I missed the "replaced" part. Did you swap out the coil or just test it?

Matter of fact this was the first thing I tested an replaced. Cut back the wires, installed MSD boots. Didn't work. Replaced coil with a known working one, didn't work again. Thanks for the thought tho.

By the way, all the extra parts are coming from a poor blaster that keeps getting bastardized by me stealing all the parts off it.

 

[Pro-pulsion]

Another thing you may need or want to try is a crank case pressure test. It should hold 8 psi for about 15 minutes before slowly decreasing. New gaskets will be needed though as you will have to remove the carb off of the manifold and the exhaust pipe completely off of the cylinders unless you make a block off plate for the headpipe to manifold mount.

 

[Pro-pulsion]

I would assume this is not the issue but is an easy item to look at, but what is the condition of your pulse hose? If it or the spigot is loose, or the hose has some rough spots on it, it may be leaking air which would act like you are describing too. A lack of fuel charge due to a drop in pulse signal to support the fuel pump, it would be more like a gasping for air but can easily be mistaken for rich conditions by the response you are describing.

 

[Jhucke]

Another thing you may need or want to try is a crank case pressure test. It should hold 8 psi for about 15 minutes before slowly decreasing. New gaskets will be needed though as you will have to remove the carb off of the manifold and the exhaust pipe completely off of the cylinders unless you make a block off plate for the headpipe to manifold mount.

A leak test is high on my priority list.

I would assume this is not the issue but is an easy item to look at, but what is the condition of your pulse hose? If it or the spigot is loose, or the hose has some rough spots on it, it may be leaking air which would act like you are describing too. A lack of fuel charge due to a drop in pulse signal to support the fuel pump, it would be more like a gasping for air but can easily be mistaken for rich conditions by the response you are describing.

No this is spot on as something so small but so easily overlooked. It's in my mind that the solution to this problem is going to be something small like that. I will look tomorrow. Another thing I was thinking of was maybe my hood is pinching off my tank breather hose. I do have issues with the hood and the check valve, I know it sits bent over in there when the hood is on.

Also a buddy of mine suggested that maybe my main fuel line could be caving in on itself at full throttle fuel pressure. It seems super unlikely, but my new lines are very flimsy. (Tygon)

 

[Freakrider]

Flimsy pulse lines are a potential problem I've learned before from Chuck of Team Scream Racing.

 

[Jhucke]

Flimsy pulse lines are a potential problem I've learned before from Chuck of Team Scream Racing.

I've heard this before as well and actually my pulse line is similar to oem style, not the squishy tygon.

 

[Rushford_Ripper]

If it was the start/stop switch, I would think it would die completely. I went through that on two skis before. That's where I'd start as its pretty easy to fix.

 

[Quinc]

When it happens does it start right back up?

 

[chixwithtrix]

I'm not a tuning guru by any means, but I'm having kind of similar issues.

I suspect reeds or a weak fuel pump in my case. Partially rebuilt my carbs, but didn't touch fuel pump.
Swapping the vent check valve and eliminating fuel selector helped, but issue returned. Some say it could be my temp sensor, but my ski is an SXR.

On my other ski my running issues were resolved with a new ebox setup. Sometimes the CDI gets weird and issues can be hard to trace.

Sorry to hear, gremlins can be so frustrating!

 

[Jhucke]

If it was the start/stop switch, I would think it would die completely. I went through that on two skis before. That's where I'd start as its pretty easy to fix.

It sometimes does die completely. I have replaced the S/S to test today after work among other things.

When it happens does it start right back up?

This is why I think it could be fuel related but I was having trouble putting it into words before. When it happens, if I let off the gas right away it will always stay running. It dies if I keep holding it open, but not right away. It loses RPM, revs back up slightly, about 3500 as if its scavenging for fuel for a fraction of a second, loses RPM again, revs back up <3500 rpm, and either dies or cycles again. So it's like its losing fuel, system catches back up slightly, then completely loses signal.

Please keep in mind that the above is not ALWAYS the case, sometimes it doesn't rev back up for the fraction of a second before dying.

It always starts right back up but it sounds really groggy almost like when you ride a ski that is extremely rich and you have to hold it wide open for it to clear out for a few seconds. Could the case described above actually be a extreme rich condition like the ski is getting an absurd amount of fuel dumped in at high RPMs and it floods out? Why did a different carb do the exact same thing? Or maybe the grogginess is a lack of fuel... I have no clue, its hard to say.