Other How Does a Return Line Make a Ski Run Poorly

[UneducatedFX1]

This was definitely not caused by water. The only thing that I did was replace the return line and it is back to normal. I have since done bigger stabs, subs, and falls and have no problem with water through the motor.

Now that I think about it, it was a little sluggish overall, probably from vapors. It is due for a carb rebuild, and when I say it is running great or normal, I just mean for this particular ski. I still don't quite understand why it would make it run completely terrible, similar to sucking in water, for the first bit. I'm still thinking that check valves in the pump aren't quite sealing and it is letting fuel drain back with a break in the return line.

I had a simular sort of issue with my Fx1 i was doing tricks fell of and when it started it kept wanting to die, pulled the carb today as we couldn't even get it to start, turns out the pulse pump is was weak and one the floats that pushes fuel through (those round disc like things that suck and push fuel) was bent out of shape and was broken so i've just order a rebuild kit, might solve your sluggish problems maybe, (sorry if this isn't helpful)
Dale

 

[waxhead]

When you have no pressure in your tank it runs funny. You can tune it out to run fine. But when you fix the pressure issue you have to retune. So most people here are right. Their ski could run just fine with no pressue. My hx800 ran with no tank pressure. The change in the URL pressure because your line fell off caused your issue

 

[nbatch95]

I would like to hear someone explain there theory behind "your ski will run like crap if your tank doesn't hold pressure."

 

[waxhead]

Sure ok. when the fuel is under pressure in your fuel tank it increases the pressure one side of the diaphragm in the carburetor.
The other side is open to atmosphere pressure the difference, while there is still pressure on the diaphragm when the tank is open to atmosphere it is less and it changes the fueling. Also as fuel flow is a direct relation to the pressure in the carburetor throat and the fuel pressure on the other side of the needle this also effects the fueling
How is that

 

[nbatch95]

I don't see how fuel pressure in a fuel line that is down stream of the fuel pump makes any difference on a running ski. Crank case pulse pulses a diaphragm witch pumps fuel though check valves to create fuel pressure in the carb. Where does this presure in the tank side of the fuel system come from? Agitation of fuel? More fuel is leaving the tank than returning this should make the tank have a negative presure. Thats what the one way valve does lets air in as fuel level decreses. While the motor is off pressure in the tank is a plus as it keeps your fuel from siphoning back to the tank and making it difficult to start.

 

[Joker]

I don't see how fuel pressure in a fuel line that is down stream of the fuel pump makes any difference on a running ski. Crank case pulse pulses a diaphragm witch pumps fuel though check valves to create fuel pressure in the carb. Where does this presure in the tank side of the fuel system come from? Agitation of fuel? More fuel is leaving the tank than returning this should make the tank have a negative presure. Thats what the one way valve does lets air in as fuel level decreses. While the motor is off pressure in the tank is a plus as it keeps your fuel from siphoning back to the tank and making it difficult to start.

Vapor pressure.

 

[waxhead]

Open your tank when you pull up at the beach does air go in or out.
Have a look at the diaphragm on the other side of the carb. That is open to atmosphere

 

[nbatch95]

I understand the tank is pressurized by agitation of the fuel I don't understand how this pressure effects a running ski. The pressure will be different with temp, amount of fuel, how agitated it is to many variables.

 

[nbatch95]

Open your tank when you pull up at the beach does air go in or out.
Have a look at the diaphragm on the other side of the carb. That is open to atmosphere

mines Always pressurized.

What are you trying to get at with the diaphragm being open to atmosphere?

 

[Matt_E]

Reference pressure for the diaphragm (which establishes popoff pressure against that reference pressure) is atmosphere. That small hole in the diaphragm cover? That's what it's for.

 

[nbatch95]

Pop off pressure has nothing to do with the regulator diaphragm.

Still don't have a good explanation of how non-pressurized fuel line will make a ski run like "crap"

 

[waxhead]

The difference in pressure between one side of the diaphragm and the other side effects your pop off pressure.
If you have reduced pressure in your tank then you have reduced pressure on one side of the diaphragm.
The fuel pump adds to the pressure thats already there

 

[Matt_E]

Pop off pressure has nothing to do with the regulator diaphragm.

Still don't have a good explanation of how non-pressurized fuel line will make a ski run like "crap"

Popoff pressure has everything to do with the diaphragm. No offense, but I think you should go back to the drawing board here if you don't understand that. The system must have reference pressure to establish what popoff pressure is.
Try taping that hole over and see how it runs.

 

[nbatch95]

Popoff pressure has everything to do with the diaphragm. No offense, but I think you should go back to the drawing board here if you don't understand that. The system must have reference pressure to establish what popoff pressure is.
Try taping that hole over and see how it runs.

maybe you should go back the drawing board because pop off pressure is made by the fuel pressure against a closed needle and seat. Once the fuel pressure has piped the beadle open it makes its way into the regulator portion. Diaphragm acting as a bowl to keep fuel in and float so when fuel runs low bypasses the pop off.

 

[waxhead]

maybe you should go back the drawing board because pop off pressure is made by the fuel pressure against a closed needle and seat. Once the fuel pressure has piped the beadle open it makes its way into the regulator portion. Diaphragm acting as a bowl to keep fuel in and float so when fuel runs low bypasses the pop off.

Ok your right sorry. Have a great day

 

[TheBuzzard]

since tank pressure varies with amount of heat causing vapor, amount of gas compaired to air in the tank, those 1 way valves not quite holding pressure, wouldnt it be stupid and a tuning nightmare to rely on varying tank pressure to insure proper tune? in my experience, the 1 way valve only affects how old 440/550s with round body carbs and weak fuel pumps run. i've never had any problem on anything with a remote fuel pump running 48s and no valve. i just took the valve off my 03 sj and it runs just the same with b-pipe , head and 38s

 

[MADMAT]

This topic has driven me crazy for years. I have felt immediate effects and corrected those effects by replacing the check valve right away.... yet I have seen countless people on the X say they can't feel it at all. Its like those few people out there who don't hit/feel/mind their rev limiters!

 

[TheBuzzard]

i guess you and your ski have a mental connection. i ride so much different stuff, i know it either runs right or it doesnt.

 

[nbatch95]

This topic has driven me crazy for years. I have felt immediate effects and corrected those effects by replacing the check valve right away.... yet I have seen countless people on the X say they can't feel it at all. Its like those few people out there who don't hit/feel/mind their rev limiters!

Is your vent under your hood? If so could it be fuel vapors leaking into your engine compartment?

 

[Joker]

maybe you should go back the drawing board because pop off pressure is made by the fuel pressure against a closed needle and seat. Once the fuel pressure has piped the beadle open it makes its way into the regulator portion. Diaphragm acting as a bowl to keep fuel in and float so when fuel runs low bypasses the pop off.

Dude quit acting like a deuche