2012 Suzuki Df9.9AES rough carb or choke issues?

nphilbro

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Dec 19, 2011
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I think I'm dealing with a carburetor/auto chocke issue. I just acquired this motor with 5 hours on it on trade after original owner gave up on it after over filling the oil and locking it up, then his dad burned up the electric starter trying to get it running again. First, I purchased a manual but it turned out to be for the older models so it's not helpful for my question. I can rebuild a OMC 2-stroke with my eyes closed so am comfortable with a wrench but not so familiar with 4 stroke operation.

I slowly worked the oil out of the crankcase and fuel system with the pull start until it would fire and actually run on its own. I flushed new fuel through the carb, pulled the plugs 8-10x to clean burnt carbon off them as the oil worked its way out. I'm having issues with low idle/rough idle at this point.

So my questions are several:
There is the electric start chocke assembly on top of the carb, I'm hand starting this motor due to the electric starter being burned out. I have the battery leads connected to to a good battery to make current available when needed and not burn up the rectifier (if it isn't already). Do I need to override this electric choke somehow?

What's the proper way to set/check the carb linkage? I've noticed I get painful a compression lockup pulling it if the rear armatures are adjusted with linkage arm sticking up higher out of the barrel lock vs. if it's flush.

I haven't completely removed and rebuilt the carb, yet. I removed the choke, drain screw, and top cover and blew compressed air into all the accessible orifaces, including the tiny idle orifaces on top of the carb with motor in gear and fully open as well as neutral/idle. There was no visible sign of oil after that but it still ran rough. I'd like to test a few simple possibilities out before pulling the flywheel and tearing the carb apart.

Again, I suspect the rough running condition has something to do with either the electric choke or throttle linkage setting. I'm working on a new motor that's already been "worked on" by someone that should never have touched it, as evidenced by the completely destroyed impeller.

Hoping you guys can give some good pointers.
 

nphilbro

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Dec 19, 2011
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I see no responses yet, so I'll share what I've done so far.

*This is after removing the carburetor, and giving it a thorough chemical and physical cleaning with a 80PSI compressed air nozzle. I hit every oriface I could see, every passageway, removed the rubber plug and entire pilot jet.

1. I replaced the spark plugs (gapped to .031) and noticed now it was only the top one getting fouled with dry black soot after running several minutes in the tank.

2. Sprayed carb cleaner into each cylinder while it was at TDC, let it soak, blew it out with compressed air, rotated the flywheel 369* and repeated until the black sludge quit coming out the plug hole. I also turned the flywheel to the exhaust struck and blew the remainder of the sludge out the exhaust system (into the tank).

3. Briefly it seemed to settle down and idled almost to spec, but still a little bumpy. I had to leave town for a few days so it sat with (new) fuel in it from Wed-Friday. I figured id just add some seafoam to the tank and problem would be completely solved.

Yesterday I went out to start it and was back to square one. with the idle issue. The low speed/idle range is where I'm not getting a carb response. Took the carb off and cleaned it as before, repeated the cylinder blast, replaced the fuel line between the pump and carb.

Any ideas on how to proceed? How do I get the auto choke to turn on and off? All I have is a green button, the Plc heater. I'm still pull starting it because the starter needs to be rebuilt but have it connected to a battery with the red wires to start jumpered and black wire grounded to the block.
 

tommarvin

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Nov 22, 2015
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999
I would do a compression test if you have a compression tester, if not consider buying a leakdown tester, HF has a leakdown test kit for 40 bucks.
Check for spark on all sparkplugs, then check timing.
Fix the starter or buy a new starter and get the motor back together 100%.
 

nphilbro

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Dec 19, 2011
Messages
304
Tore the carb down once again and worked it thoroughly on a table inside. Used a magnifier to locate every jet and oriface and used various copper wire strands to clean each one. I also found small cracks between the fuel line between the pump and carb so replaced that, it finally idled but still acts like it's running a bit lean. It will go into gear but the idle doesn't act stable and I have to keep the idle set screw turned in half way. Is it just seafoam time now?

Spark is good but haven't located a new tip for my compression tool. However, it WOULD go into gear without stalling. Is there a mix plug hiding the mix needle on this motor? If there is it seems that could speed up the workout proses to getting it run like new.
 
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99yam40

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Sep 7, 2008
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if you did not remove the idle mixture screws and clean \out those passages then you did not clean the carbs properly yet
 

nphilbro

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I was looking for the idle mixture screw plug on the diagram and couldn't find it, but I agree - that's once of the most common places that needs deep cleaning. I'm not positive this model with the "EPA" listing has an adjustable one, even if it's behind a plug that needs to be drilled out.
 

nphilbro

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No Title

Is the idle mixture screw behind this brass plug?
 

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nphilbro

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Or is it behind this plug "Option 2"? Now I seem to recall seeing a needle screw in that area. I cleaned the area really well but I know from experience they need to be removed to be cleaned completely.
 

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nphilbro

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Dec 19, 2011
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304
It was option 2. Drilled out the plug and unscrewed the needle. It was covered in a little black crud. Cleaned it up, blew it out, set the mix for best idle setting. Idled great now but going to get another new set of plugs now so I know it's firing right. It's only a trolling motor for me so it'll be running mostly in the lowest RPMs. I normally do a "hot lap" once or twice a day at high RPMs to burn any residual carbon out.
 
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