Carb Problem?

[system-f]

This might be a stupid question, but I need to be sure. This is a Rochester 2GC carb and I just put a kit in it according to the Mecrusier manual.

My question is I see gas dribble off the top of the venturi cluster down the throat when it is idling. The boat runs perfect so far save a rough idle which I think maybe vacuum related. This is NOT a gasket leak as the fuel is flowing down from above where the gasket for the venturi cluster meets. I read somewhere that there is an idle bleed on top of where the venturi cluster and float body meet, is that what this is?

See where the middle screw is that holds the venturi cluster to the body? The gas is trickling from behind there. I did put a new gasket on that screw and it is tight. Is this flow of gas normal?

 

[Bifflefan]

Re: Carb Problem?

Gas should NOT come from there at an idle. nor any other time.
the gas is running down the outside of the booster leg if im looking at the pic correctly. There is something wrong if so. did you double gasket it by accident?
As for the vacum leak, this can cause gas to spill over from the boosters. A low vacum signal is a bad thing. Fix this first. Then look at it again.
Also check the timing to make sure its correct as retarded timing can cause this too.
Also the float level may be just a bit to high.

1: Fix vacum leak.
2: Check timing.
3: Check float level, gasket under booster and for a crack in the booster leg or around the mounting screw. Also there is a gasket on the screw itself.

 

[jtybt]

Re: Carb Problem?

If you're talking about the mounting screw. it should be sealed.

I haven't done the 2 GC before but I bet if you remove the top and re-seat the venturi, it'll seat. Might be cross threaded

 

[TowRoper]

Re: Carb Problem?

i believe it is normal at idle, when at idle there is not enough suction to atomize the fuel BUT i don't know this carb very well so lets see if anyone agrees lol

 

[TowRoper]

Re: Carb Problem?

i see i type to slow sooooo never mind my reply lol

 

[system-f]

Re: Carb Problem?

there is no vacuum leak from the carb at all, I thought there might be one on the adapter plate but now I am not sure. Timing and all ignintion is good, new points, set dwell, set timing, etc.

I put a new gasket on that screw. I guess I need to pull that apart and check the float. I bet the float isn't set 100% correct even though I quadruple checked it. What is the toe of the float? Closer to the float valve or further away?

 

[Apollo75]

Re: Carb Problem?

Find that leak --- no fuel should be coming from there with a new gasket.

Idle

At idle there is an idle circuit --- it is all below the throttle plates. Should not see any fuel anywhere inside or outside the carb at idle.

Partial Metering -- Just off idle

Just off idle there are extra holes or slots just above the throttle plates in the carb walls to allow more fuel into the carb for this purpose. No main metering flow at this time either.

Main Metering

Finally when you open the throttle past idle and past the off idle ports --- and if there is enough air flow to create a low pressure area under the main venturi --- main metering will start and fuel will come out of the venturi.

My best guess is float level or a sunken float !


OFM

 

[system-f]

Re: Carb Problem?

Check float level, gasket under booster and for a crack in the booster leg or around the mounting screw. Also there is a gasket on the screw itself.

What exactly is the booster? The center screw, which is wet, that you can see in the picture has a new gasket and the gas is actually coming from behind it.

 

[system-f]

Re: Carb Problem?

My best guess is float level or a sunken float !

Float is good as far as being sealed, but it could be the level...the manual is not 100% clear.

 

[Apollo75]

Re: Carb Problem?

Well, sorry I am not there. People call parts many different names --- there is nothing in there that is really a booster. There are tubes with air mixture holes for main metering and there are tubes for metering and there is the accelerator pump ball, spring, keeper, tube and the accelerator nozzle assembly.

Booster has been referred to as the smallest inside venturi ring --- as it helps boost main metering at low throttle settings.

If you just pumped the throttle and fuel leaked there from the accelerator pump then gasket is leaking a little --- if it is tight and coming out of the nozzles also --- and you can adjust the idle mixture screws for good idle --- go have a nice day

I the engine is shaking all over like Elvis Presley --- and some fuel leaks there --- it is probably not the carb's fault.

OFM

 

[system-f]

Re: Carb Problem?

Thanks for your help. I wil check back through everything, but I think everyone has it with the float adjustment as it makes sense. Maybe the backside of the gasket is leaking and it is coming over the top. I guess I have to dig back in there...

 

[fat fanny]

Re: Carb Problem?

Gasket may not be seating correctly try rubbing a little vasilinon both sides and re-seat also make sure there is no debree whatso ever on the mating surfaces this might help .Good luck!

 

[system-f]

Re: Carb Problem?

Thanks everyone for your suggestions. I am going to try everyone's suggestions and rip this thing back apart tonight. I will take better pictures of the assembly for refernce and post back the results. Hopefully this gas leak is the cause of the not so perfect idle.

 

[system-f]

Re: Carb Problem?

I tore the carb apart and checked the float. I think I was adjusting the wrong end of the float and made sure it was set properly which it is. I am still getting fuel out of the top of the venturi stack on these two little holes, but nowhere else. No gaskets are leaking the fuel is very obviously coming from these holes. Idle has drastically improved and the engine runs good at 500rpm.

The engine is running in this picture. See how the screw is dry? Notice those two tiny holes right above the screw that is where the gas is coming from at a very very fine trickle. When I increase the idle to over 1500rpm the gas stops flowing from these holes. Does the float need to go down some? I can find no problems with the carb and all of the pieces seem to be in good order.

 

[Apollo75]

Re: Carb Problem?

Hello;

Carb upside down and float a little higher than level works every time.

Looks like this :

http://www.tocmp.com/manuals/Carbs/Rochester/2-Jet/Manual/Part2/MCarbRoch73802GPart203.jpg

Three screws holding the venturi assembly ---- inside one has shank on it ---- not all thread like the outside ones.

Good pump shot ---- can adjust idle screws for good idle --- idles nice and smooth --- quit working on it and go have fun


OFM

 

[system-f]

Re: Carb Problem?

Good pump shot, good idle, no leaks... and the exhaust doesn't smell stupid rich like before. I think I am going to just put it in the water, do the idle in gear adjustment and run it. Thanks for everyone's help.