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Hello (and help with gas fouled plugs and rough idle.)

M

Mendocino_marine_salvage

New member
Hello everyone, love the Forum used it before in the past... long-time lurker.
I have a 74 Century ski fury that I've been restoring over the last couple months it's coming out amazingly well. pictures to follow.
Last 3 or 4 days I've been working on the ccw lm318. Electonc igntion via accel dizzy, stock coil. Carter afb 6212.
The motor was known to be running as it was a replacement crate motor in the late 90s, got a couple hundred hours on it and was very well maintained.
So I did plugs changed the oil, did the impeller, put some fresh gas in it fired right up.
So now I'm fighting a severe hesitation a really lumpy and erratic idle and it's gas fouling plugs. It'll idle like this for a hundred years but if you even look at the throttle it'll pop and spit and sometimes flame out of the carb. I checked plug wiring, static timing, checked and rechecked grounds and 12v electrical.
When I disconnected the manifold vacuum source that operates the choke to hook up my vacuum gauge....when I restarted it, i thought i had fixed it...it idled great and then would rev fine but then within let's say less than 5 seconds it went back to what it's doing.
I fiddled with the fast idle screw the idle screw and the air mixture screws no changes in RPM. All the way in or all the way out generally it won't stall. The reason I haven't timed it yet is because it ran perfectly according to the previous owner and nothing has been changed so I'm assuming it's the carb.
My next step is to remove the carb clean it rebuild kit etc.
Any thoughts from the pros? I'm not a Wrench who throws money or parts at problems.
Thank you like I said love the Forum pretty awesome source. William
 
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So. I removed carb, it literally looked like it was soaked in sand. Totally destroyed plungers, float bowl cavities were packed with rust and sand. Totally fascinated by why this thing even idles at all. So now I'm making the decision whether to buy a new carb or to rebuild this one. Leaning towards just buying a carb from a reputable source and then tuning with the known good carburetor.
 
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Mendocino_marine_salvage said:
Hello everyone, love the Forum used it before in the past... long-time lurker.
I have a 74 Century ski fury that I've been restoring over the last couple months it's coming out amazingly well. pictures to follow.
Last 3 or 4 days I've been working on the ccw lm318.
CCW is standard rotation as viewed from the flywheel end.

Electonc igntion via accel dizzy, stock coil. Carter afb 6212.
The motor was known to be running as it was a replacement crate motor in the late 90s, got a couple hundred hours on it and was very well maintained.
So I did plugs changed the oil, did the impeller, put some fresh gas in it fired right up.
So now I'm fighting a severe hesitation a really lumpy and erratic idle and it's gas fouling plugs. It'll idle like this for a hundred years but if you even look at the throttle it'll pop and spit and sometimes flame out of the carb. I checked plug wiring, static timing, checked and rechecked grounds and 12v electrical.
Have you looked at the progressive ignition advance?


When I disconnected the manifold vacuum source that operates the choke to hook up my vacuum gauge....when I restarted it, i thought i had fixed it...it idled great and then would rev fine but then within let's say less than 5 seconds it went back to what it's doing.
Verify the quality of the ignition spark. Yellow or yellowish = weak spark. White or whitish/blue = good high energy spark.

I fiddled with the fast idle screw the idle screw and the air mixture screws no changes in RPM.
These adjustments should affect low speed.

All the way in or all the way out generally it won't stall. The reason I haven't timed it yet is because it ran perfectly according to the previous owner and nothing has been changed so I'm assuming it's the carb.
Check/re-set BASE advance.

My next step is to remove the carb clean it rebuild kit etc.
Any thoughts from the pros? I'm not a Wrench who throws money or parts at problems.
Thank you like I said love the Forum pretty awesome source. William
Click to expand...

Mendocino_marine_salvage said:
So. I removed carb, it literally looked like it was soaked in sand. Totally destroyed plungers, float bowl cavities were packed with rust and sand. Totally fascinated by why this thing even idles at all. So now I'm making the decision whether to buy a new carb or to rebuild this one. Leaning towards just buying a carb from a reputable source and then tuning with the known good carburetor.

Check your fuel source. Install a new filter cartridge. Make sure that the fuel lines are clean and are in good condition.
If questionable, replace all fuel lines with USCG approved lines.
Click to expand...
 
Think I figured it out. After rebuilding the carb, setting the float heights and the float drop. timing, plug wiring, and chasing various vacuum leaks. I found that when I jumpered the coil 12v positive directly to 12v battery positive that it ran perfectly. So now I'm chasing maybe a faulty ground? Any ideas are welcome. Thanks for the suggestions and moral support.
 
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