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  #1   IP: 74.87.48.81
Old 11-08-2013, 06:19 PM
steveas0321 steveas0321 is offline
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Carburator Problem??

The reason I say that with a question mark is because I'm not really sure that's the problem, but likely it is. I'm a fare mechanic but only been tinkering with friends boat (atomic 4) for a while. I'm sure I could take the carb apart and spend endless house rebuilding it. Not really into it. I was thinking of just buying a new one and being done with it. If that's a good idea? Boat is about mid 1970's 32' Islander

Engine has always ran well. Some choke problems, idle problems, but all in all not bad to live with. Well, the other day she just decided to give us fits on a short little sunset sail. Going out of the harbor died several times.... restart.... struggle.... jetty.... Made it out. Coming back in died after a couple minutes.... restart.... struggle.... jetty.... Made it to the slip. I not good with stressing about running aground.

Fresh gas, getting fuel, electronics OK. Question is to rebuild or not to rebuild? The carburetor looks simple enough but just haven't gotten into it yet. Is it worth it?

HELP!!!
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Old 11-08-2013, 06:44 PM
JOHN COOKSON JOHN COOKSON is offline
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Yes it's worth a rebuild if the carb is the problem.
Mechanical or electric fuel pump? If electric try bypassing or shorting across the OPSS (oil pressure safety switch). Sounds to me like you are running on one carb bowl full of fuel then the enging dies.

TRUE GRIT

Last edited by JOHN COOKSON; 11-08-2013 at 06:52 PM.
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Old 11-08-2013, 06:47 PM
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The carb is simple to rebuild. In many cases, you can just open it up and clean it, without replacing anything. If dirt in the carb is the problem, it may return quickly if you don't find the source of the dirt.
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Old 11-08-2013, 07:52 PM
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You didn't mention filters. These days it is necessary to have a filter/separator right at the fuel tank and a secondary "polishing" filter just before the carb. Courtesy of ethanol and your intelligent government.
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Old 11-08-2013, 08:49 PM
steveas0321 steveas0321 is offline
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Quote:
Originally Posted by Loki9 View Post
The carb is simple to rebuild. In many cases, you can just open it up and clean it, without replacing anything. If dirt in the carb is the problem, it may return quickly if you don't find the source of the dirt.
Is there a rebuild kit? i.e. gaskets, springs screws etc? Or just go for a good cleaning and hope you don't tear anything?

Adjustments?
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Old 11-08-2013, 08:50 PM
steveas0321 steveas0321 is offline
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Pretty sure filter and pump are good to go.
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Old 11-08-2013, 10:33 PM
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There are rebuild kits available from www.moyermarine.com like this one.

You'll need to determine if you have an early or late model carb to choose the right kit.

There are no adjustments inside the carb, just the idle mixture screw on the outside. Some early models also have a main mixture control (external screw) but the late models are fixed.

You may not need any parts, or maybe just a gasket that can be ordered separately.
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Old 11-08-2013, 11:02 PM
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Perhaps if you drain the bowl (plug at bottom of bowl) into a clear glass container you might see some contaminants.
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Old 11-09-2013, 06:25 PM
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You can break down the carb in 30min. Just pull it apart and have a look. Read up on cleaning tips etc. Like use a piece of wire to clean ports and jets and all of the other things to inspect. I have never used a rebuild kit. I have one but a basic cleaning always does the trick. It sounds more like a fuel pump issue. Carb will normally refuse to run, not run, need choke, not restart immediately. Check your filters and fuel lines too.

Last edited by yeahjohn; 11-09-2013 at 06:28 PM.
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Old 11-11-2013, 09:51 AM
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Easy

When I first had problems a few years ago, I thought cleaning the carb would be difficult. I was so wrong. 2 bolts to remove, 4 screws to disassemble, a new gasket (the carb had never been removed in 33 years), soaking in carb cleaner, wire in orifices, done. I experienced starting then stalling before I cleaned the carb. I'm guessing some gas got through, but then not enough. I thought the problem was the pump (a good reason to have a fuel pressure gauge), so I replaced that and things worked for a short while (probably just because it increased the pressure slightly). But then stalling returned. After I cleaned the carb, engine roared to life and has run great since.
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Old 11-11-2013, 12:37 PM
steveas0321 steveas0321 is offline
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Quote:
Originally Posted by prstack7 View Post
When I first had problems a few years ago, I thought cleaning the carb would be difficult. I was so wrong. 2 bolts to remove, 4 screws to disassemble, a new gasket (the carb had never been removed in 33 years), soaking in carb cleaner, wire in orifices, done. I experienced starting then stalling before I cleaned the carb. I'm guessing some gas got through, but then not enough. I thought the problem was the pump (a good reason to have a fuel pressure gauge), so I replaced that and things worked for a short while (probably just because it increased the pressure slightly). But then stalling returned. After I cleaned the carb, engine roared to life and has run great since.
Sounds like a good cleaning is what it needs to me as I checked everything else and all seems good with fuel system...... Likely get into it next weekend.

Thanks to everyone for comments and support. I'll post my results.
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Old 11-18-2013, 07:31 PM
steveas0321 steveas0321 is offline
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Cleaned the carb!!!!!

Everything taken off and cleaned. Pretty simple job.

One question. What is the setting for the needle valve?

When I took it out.... it was 4 to 5 full turns in clockwise..... nearly bottomed out.

Is that right? Only 1/4 to 1/2 turn is all that's left to complete bottom???

HELP???
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Old 11-19-2013, 08:56 AM
Dave Neptune Dave Neptune is online now
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Lightbulb Idle mix

Set the idle screw at 1 1/2 turns open~IE screw it all the way in to the seat GENTLY then back it out 1 1/2 turns. That is about where most idle, you will need to adjust a bit from there once running.

Dave Neptune
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Old 11-19-2013, 01:32 PM
steveas0321 steveas0321 is offline
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Carb adjustments

Can anyone help me with the proper adjustments (initial settings) on the carb? FYI - this is an older one.

1.) The fuel mix valve at the bottle of the carb...... Is there a certain setting to start with? I had it all the way in (no start). Backed it out about four full turns and engine started.
2.) There is a needle valve on the top (side) of the throat. I am assuming that's the idle screw and will set it according to last post.......
3.) I've played around with the idle screw on the throttle arm. There's no mysteries there.
4.) Engine starts with choke all the way out. Push it in about 1/4" to 1/2" in once it starts. Even after the engine is warmed up you can not push the choke all the way in or it will die..... Is that normal?

THANKS

Last edited by steveas0321; 11-19-2013 at 01:41 PM.
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Old 11-19-2013, 02:10 PM
Dave Neptune Dave Neptune is online now
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Lightbulb Also

Aha, didn't catch that is was an old style carb with the adj main jet. If I recall properly the main jet sets between 1 1/2 ~ 2 turns off of the seat. You will need to be running hard against the dock lines to adjust the main and then do a better results type adjustment when out and at hi cruising speed. You should be able to get a decent idle adjusting in the slip.

If you still have problems running without the choke check the gaskets for integrity, you may just have a vac leak.

Dave Neptune
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  #16   IP: 76.7.135.1
Old 11-19-2013, 07:19 PM
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Marian Claire Marian Claire is offline
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Found this. How do I adjust the carburetor on an Atomic Four engine?

Early model Atomic Four engines were fitted with a cast iron Zenith 61 carburetor with 2 adjustment screws, one for the high speed main jet, and another one for the low speed idle jet. Atomic Four engines after 1968 were fitted with an aluminum alloy Zenith 68 carburetor with a fixed high speed main jet (some Zenith 68 carburetors have had adjustable main jets installed), but the same adjustable low speed idle jet as the Zenith 61. Assuming the flame arrester is not partially blocked by dirt and oil, and the carburetor is clean and in good condition with the float level set properly, the proper procedure is as follows:

Carburetors with fixed high speed main jets should have the main jet removed and checked to see what jet number it is. The jet number is stamped in very tiny numbers on the face of the jet. If it is not a #21 main jet, it should be replaced with one.

To adjust the idle mixture screw, initially adjust the idle mixture screw (the upper adjustable jet with the slot for a screwdriver) clockwise (in) until it bottoms lightly, and then out 1 turn. Connect a tach to the engine, start the engine, run the engine in gear until it is fully warmed up, then close the throttle, leave the engine in forward gear, and adjust the carburetor idle speed screw (the screw on the carburetor throttle arm that controls the throttle stop) until the engine is idling at 700 rpm, turn the idle mixture screw slowly out until the rpm drops noticeably, and then in again until the fastest idle speed is obtained. Readjust the idle stop screw to again set the idle speed at 700 rpm. Repeat the idle mixture adjustment again.

Carburetors with adjustable high speed main jets should be initially adjusted by turning the main jet adjusting screw (the lower adjustable jet with the little cross on the adjustment screw) clockwise (in) until it bottoms lightly, and counter-clockwise (out) 3 turns, and the idle mixture screw (the upper adjustable jet with the slot for a screwdriver) clockwise (in) until it bottoms lightly, and then out 1 turn. Connect a tach to the engine, start the engine, and with the boat running at top speed in forward gear (or tied to the dock) slowly turn the high speed mixture screw clockwise (in) until maximum rpm is obtained on the tachometer and then counter-clockwise (out) about 1/8 of a turn until the rpm just starts to drop.

Close the throttle, leave the engine in forward gear, and adjust the carburetor idle speed screw (the screw on the carburetor throttle arm that controls the throttle stop) until the engine is idling at 700 rpm, turn the idle mixture screw slowly out until the rpm drops noticeably, and then in again until the fastest idle speed is obtained. Readjust the idle stop screw to again set the idle speed at 700 rpm. Because the idle mixture setting has an effect on the main jet setting, repeat the main jet adjustment, and then the idle mixture adjustment 2 more times.

The rationale for setting the idle speed at 700 rpm in forward gear is to ensure the engine is idling fast enough to prevent stalling or erratic running when docking. An engine speed of 700 rpm in gear will also automatically increase to about 800 rpm when the transmission is shifted to neutral, which is high enough to allow the alternator to continue charging the battery.
From http://www.cncphotoalbum.com/atomic4/faq/atomic4faq.htm
Dan S/V Marian Claire
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