Super Jet Full throttle stall??

[San Diego SN]

61x 701. Runs good untill i WOT and it will stall like its not getting enough full. Half choke and it starts to go away. What should i check? The fuel is 2 gallons relativly old( 3 months with stabilizer) mixed with 3 gallons of fresh full. I recently rebuilt the carb and replaced needle and seat but it did get stuck shut not too long ago randomly.

I still run the reserve knob fyi.

thanks in advance.

 

[Yami-Rider]

Did it run good before? or have you changed things and now it runs bad? Any ski I build i remove the fuel selector, they have gave me troubles in the past.

 

[Matt_E]

First of all, you want to stop doing that. Every time it happens, you seize the topend a little.
Second, clean and rebuild your carb(s).

 

[San Diego SN]

Ran fine intially. Carbs rebuilt because it was time. Ran fine again. Sits for a couple months for paint and footholds. And now this WOT stalling issue. Thanks matte for that its back on the trailer.

 

[burton148]

First of all, you want to stop doing that. Every time it happens, you seize the topend a little.
Second, clean and rebuild your carb(s).

What do you mean? Seize the top end with what?

 

[Matt_E]

What do you mean? Seize the top end with what?

Seize the pistons against the cylinder walls

 

[San Diego SN]

Do u guys run the stock water filter thing hanging from the port side? Where does the fuel line come form that is going into it? Somewhere on the back of the tank is what it looks like.

When i pull apart the carb what should i look for? Its looks very clean with fresh gaskets. Is there a fuel filter inside the carb? Stock mikuni 44...

thanks

 

[burton148]

Seize the pistons against the cylinder walls

I mean bypassing the fuel selector? or running WOT with choke?

 

[wanderer1]

He means running it WOT and it shutting down. He means fix the issue and don't let that happen.

 

[Yami-Rider]

Do u guys run the stock water filter thing hanging from the port side? Where does the fuel line come form that is going into it? Somewhere on the back of the tank is what it looks like.

When i pull apart the carb what should i look for? Its looks very clean with fresh gaskets. Is there a fuel filter inside the carb? Stock mikuni 44...

thanks

The water separator is part of the tank vent system. The line you see going behind your tank goes up threw your handle pole.

There is a fuel filter screen on the fuel pump side of the carburetor.

 

[Vumad]

Closing the choke is the same as letting off the throttle, less air. You're running lean. Fix the carbs before you end up buying a new motor.

Carbs get gummed up after sitting for a few months doing foot hold installs. Clean them.

 

[Matt_E]

I mean bypassing the fuel selector? or running WOT with choke?

The reason he gets it to run better with the choke is because it gives the carbs more gas through a bypass. That's a perfect indication that the motor is running far too lean and about a gnat's ass hair's width from seizing.

 

[San Diego SN]

Could a bad check valve/one way air valve on tank cause this? I can blow into it and suck air through it...

I cleaned the carbs. They looked fine, no gum, clean fuel filter, and gaskets are fresh from the rebuild kit a few months ago. I bypassed the stock fuel filter and fuel selector. Is there a way to by-pass the check valve on the gas tank?

 

[Matt_E]

You don't want to bypass that. It has nothing to do with the one way valve.
Was the rebuild kit you used original Mikuni parts? Or aftermarket?

 

[Ben Holloway]

get a new check valve on there... Matt wont this cause fuel starvation at higher RPM?

Could a bad check valve/one way air valve on tank cause this? I can blow into it and suck air through it...

I cleaned the carbs. They looked fine, no gum, clean fuel filter, and gaskets are fresh from the rebuild kit a few months ago. I bypassed the stock fuel filter and fuel selector. Is there a way to by-pass the check valve on the gas tank?

 

[San Diego SN]

I used a mikuni rebuilt kit. And it ran fine after I rebuilt the carb with the mikuni carb kit. Then it sat for a bit and caused this.

 

[Matt_E]

I used a mikuni rebuilt kit. And it ran fine after I rebuilt the carb with the mikuni carb kit. Then it sat for a bit and caused this.

Tear the carb(s) apart again and clean every orifice with compressed air. Filter, jets, passages, everything. I have seen tiny debris blocking pilot jets before.

 

[San Diego SN]

Update: Cleaned carbs again thoroughly. New check valve, fuel lines, fuel filter, and by-passed the fuel selector. Problem persists with new symptoms.

Now there is black unburned fuel pouring out exhaust (gas, not oil) takes a lot of cranking with choke on to get it started. Also, i have had the ski run away on me on the trailer before i was having problems but I'm thinking an air leak could be causing all this. I have a pro tec head and I have heard they are known to leak. Im in the process of doing a leak down test to figure out where the leak is.

Any other ideas? I appreciate the help.

 

[Matt_E]

Unburned fuel out of the exhaust usually indicates that the carbs are leaking fuel into the motor while the ski is sitting around.
Usual culprits for this:

• leaky needle & seat (did you replace those during your rebuild? They are not part of a rebuild kit!)
• low popoff pressure (what is the size of your seats, and what weight are the springs?)
• Malfunctioning tank one way valve (allows excessive pressure to build up, which pushes open needle & seat and floods motor with fuel)

Now, an air leak would be a likely candidate for the "full throttle stall" as you describe it. However, the head is not a source for an air leak.
If I were you, I would perform a leak down test on the motor. I'm pretty sure that's described in the tech FAQ somewhere.

 

[San Diego SN]

Ok thanks. I did replace the needle and seat with the rebuild. Its a 2.3. (701 protec ported, protec head, protec pipe). Not sure on spring but it ran great with that setup before. Il try to figure out the leak down test and report back.