Dual Fuel Supply Diagram With Return.

[OsideBill]

I use a 1/4" (6mm) brass barbed tee and tap the end that goes to the tank for a main jet. I will get the thread size later sorry I am at work. I start at 100 and shoot for 1-2 psi at idle and 5-7 psi at WOT. Spud just did this set-up he had only 1.5-2 psi in all positions his returns are not opened up in his carbs though so this does make a difference.

[mrbtd]

his returns are not opened up in his carbs though so this does make a difference.

I am embarrased to say I dont know what opening up the returns means ?

I know there are returns on the outside of the carbs. Do you mean on the inside somewhere like in the pic ?

[OsideBill]

I thought there used to be a post with pics but maybe it was on Riva here is what I could find here from another post. I hope it helps.



I got these instructions for a fuel pressure mod from Fercho last year on the Riva site. It works great! I think I ended up with a 95 main jet restrictor to get my fuel psi to 6 @ WOT.

"Remove the pump side of the carbs, remove the inner filter and tape the hole, drill out the restrictors on the stock carbs using a 1/8 drill bit at the same time vacuum to prevent shaving from flying around,.deburr the edges of the hole clean well and reassemble the carbs.
Connect a 3" long 1/4 in hose to the end of the return line fitting in the carbs. Connect a 1/4 Y adapter to the hose and a 80 main jet restrictor to one end of the Y adapter. Connect a 1.5 SS liquid filled Fuel Pressure gauge to the other end of the Y using a long enough 1/4 inch nose. The end of the Y that has the main jet restrictor will go back to the tank.

The idea is to build pressure between the carbs pump and the main jet restrictor and take the reading from in-between these two.

The advantage is that the pressure is equalized for all of the carbs, all 3 carbs will have the exact same PSI."

[dhoad]

Mrbtd- you are the right track. Drill out the return with 1/8 bit - not sure if that is the correct size.
that fuel restrictor you highlighted from jet-world is exactly what you want

[mrbtd]

found this..I assume I can do this same thing on stock carbs ?

[OsideBill]

That's the link from Novi I had earlier in the thread that is dead now. Good find

[mrbtd]

Has anyone tapped the return barb for a jet instead of using a in-line restrictor ? I know some of the stand up guys do this but their carbs are very easy to get to...

I am thinking the advantage to it being in-line is I could change without pulling the pipe.

[OsideBill]

I put a tee in my return line and have enough length hose so that it is accesible from the front once you remove the buket. looking through the tee I tapped the side going to the tank the branch of the tee goes to my pressure gauge. you can do the same thing with a straight hose to hose barb if you are not using a gauge. I have one if you need it.

[mrbtd]

This is the return that I need to drill out right ?

[OsideBill]

Correct that is the hole. Fercho was opening it to 1/8"

[mrbtd]

that was easy to open up. Only took me an hour to get the nerve to start drilling...

Thanks for the offer on the gauge - I am going to mount one somewhere on the cowling (maybe like Duke did his).

[Duke]

that was easy to open up. Only took me an hour to get the nerve to start drilling...

Thanks for the offer on the gauge - I am going to mount one somewhere on the cowling (maybe like Duke did his).

Yup

http://www.greenhulk.net/showthread.php?t=37537

[Hybrid AWD]

So as a nOOb I assume the purpose of this mod is to accomodate the modified ski's so there is never a chance of fuel starvation?

With our season (warmer season) right around the corner, I am trying to knock out a few things to both ski's before riding this year. I am just trying to determine if this is something I should go ahead and do.

[flyman]

Well I finall got my ski on the water this weekend. With rebuilt carbs and drilled restrictors. Brand new motor. I have a permenantly attach fuel pressure gauge. Ran the ski with 28/1 mix for first tank. I took a lap around lake perris about a 20 min. ride. It ran great! Had to control myself. Did'nt want to go over 5000 rpm on new motor. On my second lap, it died. Started back up and it ran fine. Third lap it It started to spudder. Wouldnt get over 5 miles an hour. It would just bog and die. I have a primer system on my ski. So I pumped the primer and with the throttle slightly cracked open it took off like a bat out of hell. Pulled ski out. Replaced plugs. They were light brown. Mixture screws are at 7/8 and 1 1/2. Put ski back in water and no change. any ideas?

Fuel press. is 2 psi at idle. When I crack throttle open fuel pressure goes up to 5-6 psi but ski just bogs out. I did a compression check. 110 psi on all three cylinders.


1998 xl1200 65u

[gixxedraider]

carbs: loose or bad pulse line(s); clogged jet(s), or internal filter(s); bad diaphram(s); loose parts inside carb(s)

i know its a pain but you need to pull the carbs