Rich Carb

[MGB922]

I still have a rich carb. Float is good, right needle, the enrichment valve came out of it's track ounce but is good now, have good airflow through charcoal canisters and crackcase vent, dampner is fine. What else is there to zenith on a 79B?

 

[aeronca65t]

pinhole in damper diaphragm?

 

[MGB922]

I ran out of dampner oil and using 10W 30. Would that cause it too?

 

[DrEntropy]

naah. Anything from ATF or 3-in-1 to motor oil will work. Have you got any adjustment on the needle?

 

[tony barnhill]

Is the needle flush with the carb body? (You'll have to manually lift the piston to see) Or, where is it in relation to the bottom of the carb body as you look through the air filter hole?

 

[MGB922]

Needle adjusts but doesn't do any good. I set the needle flush to the bottom of the piston before trying to adjust.
Tony
What do you mean flush to the "carb body"?

 

[DrEntropy]

I'm guessin' he means the piston.

 

[DrEntropy]

I've been cogitatin' this and... the needles in those pistons are sprung. I've seen some instances of amazing wear on both needle and jet receiver due to the needle being constantly sucked toward the intake, rubbing on the jet. Wore the orifice to a point the mixture couldn't be trimmed lean.

 

[JPSmit]

I no longer run a Zenith Stromberg on my Midget but every conversation we have had on the Spridget boards says that they just run rich. I vastly prefer my SU

 

[tony barnhill]

My '79 MGB that has always had the ZS carb doesn't run rich....

I meant to say, the jet - when you remove the air cleaner & lift the carb, & look into the hole, is the jet level with the carb body....&, is it centered in the hole? Does the needle go into the jet without hitting the jet?

 

[MGB922]

I think I'm understand what you are all saying. The needle needs to be all the way in the jet or the piston and needle need to be all the way to touch/strike the carb body where the jet sits. If the piston or needle are hung above the jet or bottom of the bore there would be too much fuel at idea which is where I'm running rich. Also, if the needle doesn't run through the jet straight and rubs on the jet it can wear the jet causing a bigger hole and more fuel. Sound right?

I do hear a clack when i drop the piston so I'm thinking it is making contact with carb body. I'll have to check the jet and needle.

How would a pin hole in the damper diaphragm cause rich carb?

 

[DrEntropy]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]
How would a pin hole in the damper diaphragm cause rich carb? [/QUOTE]

It wouldn't. It'd be leaner.

 

[MGB922]

That's what I was thinking. I thnk it's time for me to pull the carb again and go through it with a fine tooth comb. Anybody know where I could get a jet if that's what it is?

 

[DrEntropy]

Joe Curto.

 

[MGB922]

Needle ok Jet ok. What I did find was that the enrichment valve body moved back not allowing the valves needle to close all the way. Scary that it did that since there realy isn't anything to hold it in place. The float was a little high and there is a pine hole in the diaphram. Might be a combination of 3 causing the richness. I'm now looking for a way to ancher the enrichment valve in it's proper place so this doesn't happen again or casue a fuel leak. Got too much money tied up in this car to see it go up in flames.

 

[MGB922]

I safety wired the enrich valve so that it will not move. Also layed some high temp RTV in the back of it before installing the brass plug to insure no leakage. Drove it to work today at she's back in the pink. My next job is to adjust the fuel gage.

 

[Deleted member 8987]

Please note:

NEVER, as in EVER, use regular RTV in a fuel situation.

I am confident someone will say they have never had a problem, or that some NASA configured MIL-Spec version will work....but standard RTV will be attacked by fuel, swell, break apart, and plug the sXXt out of your system.

I have had to dig that stuff out of lines, carbs, pumps, just absolutely horrible.

This stuff (and a couple of others) are fuel resistant:
https://www.matweb.com/search/datasheettext.aspx?matguid=77449fa51b1d4f4093c4302056f83dfc

https://www.specialtyadhesives.com/dow_corning.htm
https://www.specialtyadhesives.com/dow_sealants/736_heat_resistant_sealant.pdf

MSDS does NOT indicate fuel or solvents compatibility

This stuff claims to be, yet MSDS does not specify:

https://www.dowcorning.com/applications/search/default.aspx?R=406EN&DCCSF=2815EN

Hopefully one of these are what you used.

I use liquid (paste) Teflon sealant.

Dave

 

[tony barnhill]

AMEN!!

 

[DrEntropy]

Yup-yup. RTV turns to slime in contact with fuel. Baaad juju. :smirk:

 

[MGB922]

Sorry I hit the alert button but I tend to use the RTV term loosly. This stuff says it can be used on a fuel system so it's not general RTV. You guys are on the ball though. I also wouldn't use any material that can beed anywhere that the beeds could brake off and clog up the works. I use an aviation type for the engine but don't use any on a carb. Where I used this stuff is at the end of the enrichment valve where there is no way it can get into the fuel system. I layed it in there as a backup in case the seals on the valve started leaking for some reason. Just don't like where is sites, over the converted and exhaust pipe and that the valve started coming out. I can't remember the name of the stuff but it did say on the tube it could be used on fuel systems. But Dave you bring up a good point about the MSDS. I was going by what the tube said an didn't look up the MSDS, maybe I'm putting a fauls hope in this stuff.