2007 Honda BF50 falls flat after carb rebuild

I have a 2007 Honda BF50AKO that keeps falling flat on throttle advancement. I have replaced the fuel tank, fuel lines, primer bulb, in line fuel filter and added a large fuel water separator. I spent over $250 on new carburetor rebuild kit to include gaskets o-rings seals needles clips and Jets. I soaked the carbs and Chem-Dip and dumped two entire bottles of carburetor cleaner into every single hole and tiny passageway outside the carburetor and inside around the butterfly valve.

I reassembled everything according to the Honda shop manual for my motor to include the air mixture screw and float valve height. I also popped in three brand new spark plugs and had spark on all three cylinders when I tested against the block.

After a few seconds of cranking and choking the motor fired up and idled decent. After the engine was warm, I installed my carb synchronizer and got all three cylinders mirroring the number three cylinder. Next I started to adjust the air mixture screw and I got no response from the top carburetor while making adjustments. It did not matter if I turned it all the way down or six turns all the way out, there was no change in that cylinder. So I started adjusting the second and third cylinder and was able to get a rpm response so I shut the engine down for further investigation.

I pulled all three spark plugs out and found the number one spark plug was wet with fuel not water and the second and third spark plug had a nice light brown color on it like I am used to seeing. (Note.... when I pulled the original spark plugs out when I bought the boat the number one spark plug was black and the number two and three spark plug were light brown)

Not knowing exactly what was going on I disassembled the carburetor and rechecked everything to see if I possibly had debris stuck in my jets and I found nothing, then dumped an entire bottle of spray carb cleaner getting every single small passage way around the butterfly valve, and every opening until it was spewing everywhere. I then reassembled and tried starting again only to have the same problem.

After fumbling through the forums for a little while I could not find anything so I called my local Honda marine dealers within a two hour radius of me to pick their brains and this is some of the ideas that came up with:

1: check the float needle and seat to see if there’s any damage because it sounds like it is getting stuck shut. (I checked that and found no issues )
2: Clean the carburetor in and ultra sonic parts cleaner for a few cycles then clean the carb again with a bottle of carburetor cleaner and blow everything out. ( I do not have a ultrasonic cleaner so I’m not able to do that)
3: Bring it in and our certified mechanics with over 60 years of carburetor rebuild in experience will get you the right. Haha
4: pull the three spark plugs out and let the fuel dry out of the engine since it is probably flooded and pop in a new fresh set of spark plugs, set the mixture screw to 1 turn out as opposed to 2 1/8 turns out and give it a try. ( I did this yesterday and won’t be home until later to try and see if this works. )

So is there anything that I am possibly missing or anything you guys have experience that I have obviously overlooked?

Have you checked valve clearances and compressions? Best to do this before messing with carbs.

As above - I would check the valve clearances and compression's. Also try a small spray of ether or fuel into the mouth of the bad carb at idle to see if that does anything. A wet plug sounds more like spark or maybe compression than fuel. The other thing that may be worth checking is the fuel pump. That could cause your engine to fall over under power.

After you check the compression and valve clearances....

You said that to start the motor, you were choking it.

I think this has a bystarter on top of the #1 carburetor. This provides a richer fuel mixture and shares it with the other carburetors.

If there is an issue with the bystarter circuit or the bystarter itself, then #1 carburetor could still be operating in the "start mode" internally. So it could be running rich, while the others are ok. In that case, the idle mixture screw will have little or no effect and the plug will be too wet to fire correctly.

Make sure that bystarter is operating when 12v is applied to it. Check to be sure that the needle is being pushed out. The manual sometimes says how far it should go.

Also, make sure that it is seated correctly in the carburetor and is sealed properly.

Also, check the base gaskets to make sure they are on correctly and not blocking the openings.

Mike

What Hondadude is refering to is called The starter enrichment SE Thermal Valve.