Who's good with carbs?

[Phantom17]

I have a rochester 2 bbl on a 1981 GM OMC 120 inline 4. The choke housing houses the choke parts, and on the back, the choke ball, pin and choke piston. After the piston is inserted, what holds it in? It looks like it should be a spring and cover, or maybe a rubber seal, something to hold the vacum. The link shows the best schematic I can find. I had (from the previous owner) a bolt, with a washer and 2 nuts holding the washer, stuffed in and glued with gasket sealer. Trying to do it right. Thanks-Jeff<br /><br /> http://www.dougrussell.com/partscat...,3347,3348,3349,3350,3351,3352,3353,3354,3355

 

[Silvertip]

Re: Who's good with carbs?

It's been awhile, but I think a welch plug is used to seal the housing. No springs in there.

 

[Phantom17]

Re: Who's good with carbs?

Any idea where I can find one? I just combed a huge used auto parts "dump" for a 2 bbl, and found 3, all non GM. It's not the heat tube part, thats in tact.

 

[Silvertip]

Re: Who's good with carbs?

Measure the opening carefully. Your local auto store should have them.

 

[Silvertip]

Re: Who's good with carbs?

If it slowly ran worse, you need to do some choke adjustment work. With the engine cool, open the throttle a little. Loosen the three screws on the choke cover and rotate the cover counter-clockwise. The choke butterfly should open as you rotate the cover. Then rotate the cover clockwise until the butterfly just closes. Tighten the cover screws. When you start the engine, the piston you were trying to seal, should pull the choke open a little. If it doesn't blip the throttle. If it still doesn't open, you still have something wrong with the choke linkage. The heat tube, or electric heater coil should open the choke the rest of the way as the engine warms. Remember, make choke adjustments on a cool engine.

 

[Phantom17]

Re: Who's good with carbs?

OK, I got one, popped it in, hooked the h2o, started the engine, and it slowly ran worse and worse......It seems like thats the right part, but with the homemade seal that was there before, it ran ALOT better. I'm thinkin' locktite!!!!!!!!!!!!!!!<br />Thanks for your help.-Jeff

 

[Phantom17]

Re: Who's good with carbs?

OK, now that you have me back into this one (which I really appreciate), I removed the plug last night, which I had to remove the choke body to do. I will install the second one (I got 2). Now I'm not sure how tight I should wind the choke thermostat coil on installation? So;<br /><br />Q1 is, when installed, (I'll call this coil tension "0"), should I turn the thermostat spring x number of times clock / counterclock wise, or at no tension at all, before I make the cold adjustments you mentioned? Thanks again, appreciate your help.-Jeff

 

[Phantom17]

Re: Who's good with carbs?

I installed a new plug, reistalled the choke housing, and set the line on the cover to the middle of rich and lean. Tried getting it running and drained the batt trying. Nothing but a few coughs. How sensative is the setting between rich and lean. Is a turn either way less than one eight of an inch a good try to find the right setting, or is it the entire dial? Ive been doing minute turns until I get a "better" cough (meaning there IS combustion".

 

[Silvertip]

Re: Who's good with carbs?

Why did you remove the plug again? You do not wind the spring. When you install the cover, just make sure the tab on the spring catches the tab on the linkage the piston is connected to. As you rotate the cover clockwise (probably less than 1/4 turn), it carries the choke plate closed (have the throttle open when you do this and the engine MUST be cold). Rotate the cover until the choke plate just barely closes. This should put the pointer on the cover somewhere near or close to the center marks on the housing. Those marks are simply reference point and serve little use for the actual adjustment. Again, when you start the engine, vacuum on the piston pulls the choke part way open (about 1/8-inch or so. If the engine runs too rich at that setting, try rotating the cover counter clockwise one-notch. As the engine warms, the spring heats up and releases the choke plate until it finally stands vertical. With the trottle open (engine off and cold) if there is any binding in the choke linkage, you need to get that freed up.

 

[Phantom17]

Re: Who's good with carbs?

I removed the old plug last night, so I put in a new one. <br /><br /><br />Just re-installed everything. Turned COUNTERCLOCKWISE to close the choke plate. Tried it, went leaner....and leaner....and leaner until wallah! Had to adjust the idle setting as the carb spit gas straight up if I hit or reduced the throttle too fast, but it ran better than ever! Actually solved my smoke problem too (ran too rich). <br /><br />Thanks, it's people like you Bondo, Don, Boomer, Marine tech, Achris, etc etc that not only make this forum fun to read, but help us novices learn to do things right. Thanks again.-Jeff