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TJTony 05-14-2019 09:42 PM

MC2100 Help
 
6 Attachment(s)
I bought a MC2100 last year, and finally got around to installing it in my 85 CJ7 Laredo, which had a weber 32/36, and have a few questions. I thought I had purchased one with an electric choke, but i do not see where i'd hook up the choke wire- is this a manual choke (first 2 pics)? There are also 2 inlets on the carb, a smaller one by the choke, and one in the back by the firewall (3rd and 4th pics)- what are these for? Finally, there is an opening on the top of the carb, that closes when you give it gas (5th and 6th pics). i was revving it, and a bunch of gas came out. I still have to adjust the linkage, and get an air filter, and maybe remove some of the old emissions, but it did run without stalling. Thanks-

ECJ-7 05-15-2019 04:27 AM

Quote:

Originally Posted by TJTony (Post 40618783)
I bought a MC2100 last year, and finally got around to installing it in my 85 CJ7 Laredo, which had a weber 32/36, and have a few questions. I thought I had purchased one with an electric choke, but i do not see where i'd hook up the choke wire- is this a manual choke (first 2 pics)?



There are also 2 inlets on the carb, a smaller one by the choke, and one in the back by the firewall (3rd and 4th pics)- what are these for?

https://www.jeepforum.com/forum/f8/mc2100-help-4355865/

Finally, there is an opening on the top of the carb, that closes when you give it gas (5th and 6th pics). i was revving it, and a bunch of gas came out. I still have to adjust the linkage, and get an air filter, and maybe remove some of the old emissions, but it did run without stalling.



Thanks-

1) It is an automatic thermostatic choke. It draws heat by the choke stove to automatically open the choke.
2)You need to find the emissions diagram to figure out what lines you need and what you can eliminate.
3)That is a vent, if it is spitting fuel, the float may be set to high.

jeepdaddy2000 05-15-2019 05:54 AM

Quote:

There are also 2 inlets on the carb, a smaller one by the choke, and one in the back by the firewall (3rd and 4th pics)- what are these for?
Pic 2 and 3. The two tiny holes facing forward on the hoke housing are mounting holes for the heat shield. The brass nipple at the bottom of the carb is the vac adv.
Pic 4. The fresh air inlet for the choke. The rubber choke line seen at the bottom of the picture connected to the choke should be a steel line running down to the choke stove in the exhaust manifold. If you are going to keep the thermo choke and don't have a stove stock in the manifold, you can use a section of brake line and wrap it around a section of the exhaust manifold. The other end should stick up close to the back of the carb and a rubber vacuum line will link it to the brass nipple. This will provide air heated by the exhaust manifold to the bi metal strip in the choke cap. If you are going to convert to an electric choke, you will need to connect the lower hose directly to the nipple, as most early MC series have the choke pull off internal to the housing and the vacuum will be needed to operate it
Pic . Float bowl vent. If you are getting fuel through here, you have a float level issue.

uptillnow 05-15-2019 10:50 AM

2 Attachment(s)
I think Jeepdaddy2000 has this figured out.

I was looking at my notes, when I worked on a few of these 2100/2150's.

1.08 venture #47 jet (1.08" x 25.4 = 27.43mm venture)
1.21 venture #46 jet (1.21" x 25.4 = 30.73mm venture)
6.5 power valve @ 3000 ft and up
7.5 power valve to 3000 ft
the power valve choice was estimated at 80% of the driving at these altitudes, seemed to work well.

I stole these pictures from somebody's post (??) for clearance issues and vacuum leaks. Take a look.
UTN

TJTony 05-15-2019 02:04 PM

Quote:

Originally Posted by jeepdaddy2000 (Post 40618957)
Pic 2 and 3. The two tiny holes facing forward on the hoke housing are mounting holes for the heat shield. The brass nipple at the bottom of the carb is the vac adv.
Pic 4. The fresh air inlet for the choke. The rubber choke line seen at the bottom of the picture connected to the choke should be a steel line running down to the choke stove in the exhaust manifold. If you are going to keep the thermo choke and don't have a stove stock in the manifold, you can use a section of brake line and wrap it around a section of the exhaust manifold. The other end should stick up close to the back of the carb and a rubber vacuum line will link it to the brass nipple. This will provide air heated by the exhaust manifold to the bi metal strip in the choke cap. If you are going to convert to an electric choke, you will need to connect the lower hose directly to the nipple, as most early MC series have the choke pull off internal to the housing and the vacuum will be needed to operate it
Pic . Float bowl vent. If you are getting fuel through here, you have a float level issue.

thanks- In pic 2, there is a narrow brass nipple below/in front of the choke, pointing straight out towards the valve cover. in pic 3, there is a thicker brass nipple going out at an angle in the rear corner of the carb. did you mean this one is the vac advance? if so, what is the narrow one for? I don't know if i have a stove stock.

TJTony 05-15-2019 02:06 PM

Quote:

Originally Posted by uptillnow (Post 40619287)
I think Jeepdaddy2000 has this figured out.

I was looking at my notes, when I worked on a few of these 2100/2150's.

1.08 venture #47 jet (1.08" x 25.4 = 27.43mm venture)
1.21 venture #46 jet (1.21" x 25.4 = 30.73mm venture)
6.5 power valve @ 3000 ft and up
7.5 power valve to 3000 ft
the power valve choice was estimated at 80% of the driving at these altitudes, seemed to work well.

I stole these pictures from somebody's post (??) for clearance issues and vacuum leaks. Take a look.
UTN

Thanks- i bought my adapter from Gronk, i didn't notice any clearance or vacuum issues-

jeepdaddy2000 05-15-2019 10:25 PM

Quote:

Originally Posted by TJTony (Post 40619507)
thanks- In pic 2, there is a narrow brass nipple below/in front of the choke, pointing straight out towards the valve cover. in pic 3, there is a thicker brass nipple going out at an angle in the rear corner of the carb. did you mean this one is the vac advance? if so, what is the narrow one for? I don't know if i have a stove stock.

Pict 2:
The small brass nipple toward the front and low on the body of the carb is the vac adv,
The larger nipple above and behind the choke is the fresh air inlet for the choke housing.


Personally, I would opt to switch to an electric choke.

John Strenk 05-16-2019 12:55 PM

1 Attachment(s)
Yes, switch to electric choke.
They didn't have a choke stove on the exhaust since they went with an aluminum intake manifold. although Jeepdaddys Idea of wrapping a brake line is cool.

Do make sure to plug those connections if you don't use them. there is a vacuum supplied to the choke housing to draw heated air from the choke stove. If you don't plug it it will suck in a lot of dirt and jam your choke housing.

https://www.carburetor-parts.com/ass...ke_circuit.JPG

https://www.carburetor-parts.com/Mot...al_ep_422.html

Same for the upper fresh air intake. You don't want to be sucking dirt into your engine either.

attached pictures, Choke heater in CJ's up to early 80's

jeepdaddy2000 05-16-2019 11:14 PM

Quote:

Originally Posted by John Strenk (Post 40620479)
Yes, switch to electric choke.
They didn't have a choke stove on the exhaust since they went with an aluminum intake manifold. although Jeepdaddys Idea of wrapping a brake line is cool.

Do make sure to plug those connections if you don't use them. there is a vacuum supplied to the choke housing to draw heated air from the choke stove. If you don't plug it it will suck in a lot of dirt and jam your choke housing.

https://www.carburetor-parts.com/ass...ke_circuit.JPG

https://www.carburetor-parts.com/Mot...al_ep_422.html

Same for the upper fresh air intake. You don't want to be sucking dirt into your engine either.

John, if you plug the hot air inlet, there won't be any air movement inside the housing. This will keep the choke pull off piston from moving properly(there needs to be a pressure differential on either side of the piston). The best way to fix all this is to just connect the hot air inlet directly to the fresh air inlet and be done with it.


The brake line trick works great with headers......

John Strenk 05-17-2019 07:06 AM

Quote:

Originally Posted by jeepdaddy2000 (Post 40620977)
John, if you plug the hot air inlet, there won't be any air movement inside the housing. This will keep the choke pull off piston from moving properly(there needs to be a pressure differential on either side of the piston). The best way to fix all this is to just connect the hot air inlet directly to the fresh air inlet and be done with it.


The brake line trick works great with headers......

Good point.
There is a small bypass along side the piston that originally used to draw warm air into the chamber, the pressure in the chamber will eventually equal out and the piston will move back.

Not sure how quickly this will happen and eventually the e-choke heater will open the choke up all the way.
But it's the in-between time when a cold engine starts and needs some air to idle until it warms up. That's when it critical for the pull off piston to operate properly or die.

At least stuff some filter paper up inside the intake port. Or drill a small hole in a cap to cover the port and put in a small amount of filter paper inside the cap.
You could use a brass cap or even a plastic plug to do this.

I've seen far too many of jammed chokes with dirt/soot that have to be cleaned out to make the choke work properly.

I wonder how they do that with a MC2100 designed to work with an e-choke.

MC 2100 Service Manuals: https://drive.google.com/open?id=1NT...eiY4-Ynp5jryZ5

TJTony 05-17-2019 09:38 PM

thanks for all the info. i have to go through the plumbing and see what i can eliminate. i don't have everything hooked up right, but drove it tonight, and it hasn't ran this well in years. it seemed to skip a little when going up an incline, and puttered a little, but it still ran pretty good.

jeepdaddy2000 05-17-2019 10:05 PM

Quote:

Originally Posted by John Strenk (Post 40621139)
Good point.
There is a small bypass along side the piston that originally used to draw warm air into the chamber, the pressure in the chamber will eventually equal out and the piston will move back.

Not sure how quickly this will happen and eventually the e-choke heater will open the choke up all the way.
But it's the in-between time when a cold engine starts and needs some air to idle until it warms up. That's when it critical for the pull off piston to operate properly or die.

At least stuff some filter paper up inside the intake port. Or drill a small hole in a cap to cover the port and put in a small amount of filter paper inside the cap.
You could use a brass cap or even a plastic plug to do this.

I've seen far too many of jammed chokes with dirt/soot that have to be cleaned out to make the choke work properly.

I wonder how they do that with a MC2100 designed to work with an e-choke.

MC 2100 Service Manuals: https://drive.google.com/open?id=1NT...eiY4-Ynp5jryZ5

I'm not sure where any dirty air will come from. The manifold vacuum port is inside the choke housing. It draws clean air through the brass nipple on the top of the carb (inside the air cleaner) down through the heat sink in the manifold, then pulls the heated air up into the choke housing. The entire system is sealed with the only opening being again inside the air cleaner.



I've seen the heater tube break/rot at the connection to the manifold. This will allow dirty air to be drawn into the system.



If I remember correctly, early models were a combination of electric and manifold heat. Later models used an external pull off.

TJTony 05-18-2019 08:17 AM

the air filter stud i bought, spectre 4213 5"x 1/4" 20 thread, is not screwing in- do i need 5/16"? there is mr gasket 6399, comes with an adapter, says its for dominator carbs...


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