bs38 needle and seat

[eosdelb]

Hello everybody,
Has anybody had a problem with a bs38 carb letting a stream of gas run out of a pod filter about the same diameter as the inside of the fuel hose coming into the carb?
I can take the carbs off and pop off the bowl and nothing seams to be binding, no trash. This is the second NEW needle and seat. Put the bowl back on and pop them on the bike and open up the petcock and everything is great. Go for a ride and turn the bike off and turn the petcock off. ((((( get ready to start it again, turn on the petcock and a stream of gas comes pouring out!!!)))))

I just thought of something, should I leave my petcock open?
Am I causing the problem by closing the petcock on a hot bike?

Is there a rubber tipped needle I could use?

Im glad there are people smarter that me. I would appreciate it if someone could help me here. Throwing new parts at it hasnt helped.

 

[eosdelb]

I just took them off and checked for something at the needle and seat and found nothing to keep it from operating. The float level is at .937 from the gasket. I dont see anything wrong. I put it back together.
((((This time it still leaks.)))) I took a picture of where the gas was coming out of but I dont see where you upload it. I see from a url but not from my computer.
Oh well.

 

[gggGary]

is there fuel in the float? (leaky floats are a common problem)

 

[grizld1]

You're doing the right thing to turn off the fuel as soon as you stop and the float setting is definitely high enough. Have you checked both sides of the float to be sure it's level? If it isn't, that can cause a bind. Check the float pin; is there any possibility the float could be binding on it due to a bend, etc.? It's not unheard of to find a very small burr or other irregularity in the float needle seat; sometimes lapping in the needle lightly with Simichrome or similar fine polishing compound straightens things out. Finally, could the float have taken on a little fuel and lost some buoyancy?

 

[eosdelb]

I checked the float. It is dry inside. I checked the pin. It is smooth. I have tryed to move the float on the pin to each side and manually get it to hang up and it wont. The little spring pin in the needle works fine and comes out to the same position every time. Ive checked it about ten times with a pair of calipers.

 

[eosdelb]

Thanks for helping everyone.

 

[gggGary]

here's the pics. I would open my gas cap and see if the carb still leaks.

 

[eosdelb]

Both sides of the float are set at within .010 of an inch of each other. Im a bit of a nut about stuff like that. I couldnt live with one side higher than the other. The pin Is straight as can be. I grabbed it in a drillpress and it spins true. There is something I am not seeing. Im looking at the carb guide where the gas is routed. Maybe the PO somehow spread the two float cans apart and it is catching on the inside of the bowl. I guess I will take them off again tomorrow.

 

[eosdelb]

Ok i will try opening the gas cap first. Please tell me more. I have a peanut (harley) tank with a pingle petcock. Hose down to a inline filter that then splits off to go to each carb. I will post tomorrow evening. Thanks

 

[Sundie]

what height are your floats? they should be 22mm *from the lip*, or 24mm *from the base of the gasket*.

 

[gggGary]

My take is; that isn't a mis-adjustment or leak, that is pressurized gas being forced out through the carb. So my suspicion is that the gas cap vent is blocked.

 

[Sundie]

<ponder> So your theory is that the fuel heats up enough to cause air expansion in the gas tank to force that kind of stream out?

That's a lot of pressure, and way more than can be accounted for by expansion, IMHO.

 

[Visegrippe]

Well, gas IS highly volatile, (evaporates easily), and will build up quite a bit of pressure. I wouldn't be surprised if going from cold to running temp in a sealed tank generated 10psi or more.
(It's been too long since my chem classes toremember the math)

Posted via Mobile

 

[grizld1]

Pressure can only build up if the tank isn't venting through the cap, and when that happens you get fuel starvation at speed. If would take near-total blockage to retain pressure when the bike's been parked for awhile; if the engine isn't losing power at cruising speed, the cap is venting.

 

[650sf]

This may seem obvious, but did you replace the washer when you replaced the seat?

 

[eosdelb]

Hey everybody, I tryed the gas cap. There was no change. 650sf, There is a thin aluminum washer under the seat. Is that significant?

 

[eosdelb]

Can those spring be too weak in the needle? Seems like when I adjusted the float the spring let the pin sink down a quarter of the travel.
Do you adjust the float touching the float tang to the top of the needle pin or let the weight of the float push down the spring pin (letting gravity find its level) as I did?

 

[eosdelb]

There aint a speck of dirt inside here anywhere. The tang has no problem as it rubs against the needle pin. Im going to give up for tonight. staying up all night wont help.
Thanks again

 

[650sf]

Hey everybody, I tryed the gas cap. There was no change. 650sf, There is a thin aluminum washer under the seat. Is that significant?

I was just making sure gas wasn't leaking around the seat if the washer was missing.

 

[eosdelb]

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html
says dont compress the spring. I will reset them and try again. Did not know this. I never saw a needle with a spring in it either.