carb petcock questions 81 gs750l mikuni's

[Anonymous]

i have had my gs750 sitting in the garage for about 4 years,figured i try and start her up....didn't happen
i took the carbs offf....yuck hey were so dirty and some old gas must have gotton in the bowls even though i drained em
soaked the carbs overnight, # 2 flooding out spurting out of the tube between # 1 and #2???
i had a few hoses off it must have used it for something else
on the petcock theres the main and the vacuum line where does the vacuum hook to on the carb and theres another inlet coming off the tank.....where's that go i forgot! LOL

[earlfor]

Re: carb petcock questions 81 gs750l mikuni's

The vacum line connects to the #2 carb on the fuel side. The hose fitting is on top beside the jet.

Earl

i had a few hoses off it must have used it for something else
on the petcock theres the main and the vacuum line where does the vacuum hook to on the carb and theres another inlet coming off the tank.....where's that go i forgot! LOL

[Anonymous]

the other line

The only other line to the tank would be a drain hose coming from the fuel guage sending unit.

[Anonymous]

theres a square like box built right under the tankwith the fuel gauge wires coming out and an inlet to hook some hose for fuel or vacuum?? not on the PETCOCK the tank
anyone >????

[moto_dan]

theres a square like box built right under the tankwith the fuel gauge wires coming out and an inlet to hook some hose for fuel or vacuum?? not on the PETCOCK the tank
anyone >????

I believe that is for an overflow or vent and uses a length of tubing that runs back to the air cleaner area and does not connect on the other end.

[Jay B]

On most GS's there should be 3 hoses on the tank. On the right side (as you ride) by the fuel guage unit is 1. Its a vent hose and connects to nothing. Just thread it down towards the bottom of the bike.

On the left side there are 2 hoses.

1 comes from the vacuum side of the petcock (the inlet on the petcock usually points up and/or towards the front of the bike) and will either route to the front of #2 carb or between #'s 1 and 2.

The other come from the fuel outlet side of the petcock (The outlet ususally points either down or to the rear of the bike)and routes to the airbox side of the carbs between carbs 2 and 3.

[Anonymous]

thanks guys!
i have one more question
on the petcock the down position should the gas free flowly or just on prime...when i first turn the gas on ...think i have petcock problems ,when its on prime gas is spurting out of the overflow on the carbs between #1 and 2
what should i inspect on the petcock to see if its workin right???
or could it be a float not closing but i soaked my carbs for a few days so i would imagine there clean?

[Anonymous]

Feeling so fresh off the carb scene...

There is an overflow between #1 and #2 and then again between #3 and #4 carbs. If fuel is pouring out of these, then either the float needle and seat are not closing or float is set too high, or the o-ring around the seat is bad and even if the float closes the fuel keeps a'comin. There are also o-rings on the two vent t's and the fuel inlet T and the two cross-over couplings between 1&2 and 3&4, so make sure you determine the fuel that's a'pourin is coming from what fitting. If you had hoses on the overflow T's, this fuel should be coming out away from the carbs -- off the engine. That's what the two long hoses from the carbs do -- divert fuel away from the hot engine and hopefully onto the ground (hum, I wonder if the EPA knows about this...).

The fuel petcock is vacuum operated, so it only "flows freely" when the valve is in the Prime position. It requires vaccum from the #2 carb to open the valve in the Run and Reserve position. This hose goes to the backside of the petcock (the smallest of the two hoses on the petcock).

Sounds to me that you may need to also replace all the o-rings in these carbs too. Unfortunately, the carb kits don't usually have the interconnecting o-rings, and I was lucky to have a bulk o-ring kit. You should be able to find appropriate o-rings locally, though.

Good luck!

Roger Moore

[Anonymous]

Oh, yeah...

Did you totally dissasemble these carbs when you "soaked" them? Rubber, like o-rings, would not have survived this. In any case, how far down did you go taking these apart?

Roger

[Anonymous]

I just took off the bowls and put the carbs in sideways in the pan ,took the floats off the next day and cleaned the float jets and pilot jets -blew em out with the compressor, i couldnt get the top part screws off of the carb where the diaphrams are.
#2 float wasn't springing up like the rest....think it needs a better cleanin maybe?

[Anonymous]

I just took off the bowls and put the carbs in sideways in the pan ,took the floats off the next day and cleaned the float jets and pilot jets -blew em out with the compressor, i couldnt get the top part screws off of the carb where the diaphrams are.
#2 float wasn't springing up like the rest....think it needs a better cleanin maybe?

does the #2 float have liquid in it??

[Anonymous]

slowpoke- thats a good question,tommorow i'll turn the bowl screw and see.

[Anonymous]

slowpoke- thats a good question,tommorow i'll turn the bowl screw and see.

No doubt that seeing if there is fuel in the bowl is a good idea. HOWEVER I WAS JUST REPLYING TO YOUR SAYING THAT THE FLOAT WAS NOT SPRINGING BACK. i MEANT TO PHYSICALLY CHECK THE FLOAT ITSELF TO SEE IF LIQUID HAS LEAKED INTO IT AN THEREBY RENDERED IT NO LONGER BOYANT OR TOO HEAVY FOR THE SPRING TO SUPPORT

[SqDancerLynn1]

if you soked the carbs in carb cleaner you will need to completely disasemble them and replace all of the rubber orings Check with robert Barr of complete set of O rings $12 very quick delivery. do a gs forum search ( robert Barr) to find the ordering info

[Anonymous]

Did you "dunk" these carbs in carb cleaner "sideways"? Do they have vacuum operated sliders? If they do, you may have ruined these because they are made of rubber. If you couldn't get the screws off, get a $10 impact screwdriver and support the carbs well and get those covers off. I'm concerned now about these diaphrams.

You also really need to take these apart totally and do the cleaning one at a time to get these right. Trust me, I thought I had done it to the tee, but I found these carbs just require that nothing is overlooked. It may be the difference between success and repeated failure. The carb kits I bought for mine were $15 a piece and had all the new jets and o-rings (except for the ones between each carb), so you may want to look into these. In reality, I could have got by with just all new o-rings because all the jets were fine. The needle and seat were both made of metal, so they were good (no wear looking at them under glass).

Also, I took the floats off and dunked them all in a jar of gas and pushed them all down overnight. Then in the morning I released them and let them float and checked that they all floated up to the same height. These are compressed foam/plastic floats and I'm told they can get saturated. You did take them off too before you dunked them in carb cleaner?

Roger