Gas Tank Mod.

[SuperDrifter]

Following Group K's directions for tuning carbs, I came across something that was different than what I've thought.

GROUP K

"Pressure test fuel system - All pwc utilize a sealed fuel system that has a check valve on the gas tank vent. This check valve (which permits pressure in the gas tank but not out) causes pressure in the gas tank that helps deliver fuel to the carb(s). Any air leak in the fuel system that permits the leaking off of this pressure, will also affect fuel delivery to the carb(s) at low speeds. To test for leaks, follow this procedure. 1) remove the return line from the fitting on the carb. 2) Blow into the return line while sealing off the return fitting on the carb with your finger. This will pressurize the entire fuel system. In a quiet room you'll be able to hear any remaining leak in the fuel system. When you remove your finger from the fitting on the carb, fuel will eventually drip out indicating that the float chamber is primed full of fuel."

Aren't gas tanks setup to vent? Pressurized tanks make sense, but where does pressure buildup release? :Eyecrazy:

I pressurized my tank and found air leaks @ areas where I relocated the internal fill opening. What is the best way to seal the polyurethane pieces? Is there an Auto parts, 'off-the-shelf' product that could work, ie. Seal-all?

 

[Idok]

yamabond, hondabond or 1211

NO SILICONE!

 

[DAG]

ducktape the fix all


...jk/jk/

 

[SuperDrifter]

I would be the 1st to use duct tape, but not here :Banane09:

Any auto store products?

 

[restosud]

his description of venting the tank isn't accurate.
if the tank has pressure in it,it will not help the carburators get fuel as they return fuel to the tank as well so the whole system becomes pressurised negating the effect.

use hylomar or even 5200 to seal it assuming the gaps aren't too large.

 

[SuperDrifter]

his description of venting the tank isn't accurate.
if the tank has pressure in it,it will not help the carburators get fuel as they return fuel to the tank as well so the whole system becomes pressurised negating the effect.

use hylomar or even 5200 to seal it assuming the gaps aren't too large.

so....pressurizing is not important? Or even wanted?

 

[onesojourner]

I just talked to Chuck at Xscream and he said the tank does not need to be pressurized for the carbs to run correctly.

 

[SuperJETT]

The vent valve does 2 things: lets air in to replace the fuel that has been consumed and holds a certain pressure to prevent fuel vapor from filling the engine compartment creating an explosive environment. However, it does open after a certain pressure (5psi I think) to relieve pressure and prevent the gas tank from bursting or lifting the needles in the carbs which would then flood the engine.

 

[SUPERTUNE]

The vent valve does 2 things: lets air in to replace the fuel that has been consumed and holds a certain pressure to prevent fuel vapor from filling the engine compartment creating an explosive environment. However, it does open after a certain pressure (5psi I think) to relieve pressure and prevent the gas tank from bursting or lifting the needles in the carbs which would then flood the engine.

That's his problem....floods the carbs after he shut off the engine.
Once the carbs prime up, the check valve really has no running effect. I told him to help find maybe a bad check valve would be to put in a 60 or 70 main jet screwed right into the nipple of the tank and remove the check valve for now and use a few coils of hose zip tied the the tank straps to test and see why his carbs are leaking. I sent him all new Mikuni parts but he's still having problems...