Honda BF20D5 woes...

Hello, I have a 2005 Honda BF20D that only has 8 hours time on it (long story). Anyhow, the motor has never idle smoothly whether hot or cold from day one. When I bought it and questioned this fact the guy said "well, they all run kinda rough until they break in". Anyhow it was stored for many years in a dehumidified garage and was started occasionally but it never idled right.

I have done the following to it ..Replaced: Fuel Chamber, Carburetor (not rebuilt but replaced with new one), new fuel enrichment valve, engine oil, filter, gas filter, fuel lines, water pump, new portable gas tank, primer bulb, hose and gas is fresh, waiting for new spark plugs.

Still after this nothing has changed it continues to run poorly at idle whether hot or cold. I have noticed some white smoke at start up sometimes. Checked plugs they are dry but black (I thought it was from the oil I put in the cylinders burning off). Pulled each plug wire and motor stumbles badly so I guess its firing ok. Also seems to be idling rather slowly when cold, shouldn't it be faster when cold? I did not mess with the carburetor idle screw since I assumed it is set at the factory.

Seems to me that whatever has caused this likely existed from day one and is still there but what that is, I don't know. Sure would appreciate any ideas at this point. Thanks in advance.

When you start this motor, it should start at a rather fast idle then gradually reduce to about 900 plus/minus 50 rpm. I like to set it on the high side. The idle is reduced by your new fuel enrichment valve closing down the passage for the extra fuel/air needed at start up.

I would not assume that the idle stop screw is set correctly out of the box. So you may need to make some slight adjustments.

Getting new spark plugs is good....especially if the old ones are black.

Check your oil level and make sure it is about 1/4 inch below the full mark. Too much oil will affect the running and cause fouled plugs.

If your motor starts but does not reduce in rpm, then you have an issue with the extra fuel/air mixture. Check the voltage to the fuel enridhment valve and make sure it is there while the motor is running. Usually about 12 - 18v ac. You attach you meter before you start the motor.

Pulling one spark plug wire will actually open the circuit to both spark plugs. So a cylinder drop test on this motor is not conclusive. Both plugs fire off the same coil through both spark plugs to ground.

Three other things that you have not mentioned or tried that could also affect the idle are...
1. Bad compression
2. Valve clearances not in spec
3. Thermostat stuck open and not allowing the motor to warm up to temperature

One other thing....since it was stored for a long time, critters could have got into it and built a nest. Make sure all vent hoses are clear as well as the crankcase vent that goes from the valve cover to the carburetor muffler.

Mike

Hi,

Sorry you're having problems with your 20. They are GREAT outboards! While Mike is the resident expert and his advice is pretty much gospel (yes, he's THAT good!), Something came to mind while reading his response to you.

I wholeheartedly agree that, at this point, you should really perform a compression check to verify both cylinders are about the same and contributing equally. Equal compression in both cylinders can be considered good "balance" and is pretty crucial to engine operation.

When Mike mentioned that critters get into passages and can foul things up...it made me think of something I saw once on an 8hp that was stored a long time. Wasps that I call "dirt dobbers" had built a mud nest under the cowl right on the edge of the cam sprocket that the timing belt drives. I remember thinking: "if the engine started with that big clump of dirt there, it could cause the timing belt to jump and maybe even break".

I'm not saying that is what is wrong with your outboard but in the course of doing a valve lash check/adjustment followed by a compression test on both cylinders....the timing should be verified as well.

The blackened spark plug ends do suggest RICH running and that would indicate something is up with fuel delivery. But I wouldn't go back to carburetor UNTIL the valve train adjustment and timing is checked.

Sadly, I have to tell you that I have found dirt particles in SEALED, BRAND NEW carburetor parts purchased from Honda. I believe that it is residue from the casting process for the parts that didn't get thoroughly cleaned out. So, it is VERY possible that your new carb may be contaminated in that way.

Could it also be possible that you may have been sold the WRONG carburetor for the application? A carb that has larger jetting could cause over fueling and that may show up in poor idle al;ong with blackened spark plugs.

The "white smoke on start up" is concerning because there is no white smoke per se'. What most people refer to as "white smoke" is typically STEAM....and that COULD indicate water is somehow getting into the combustion chamber. IF that were the case, that could cause lower combustion temperatures and might result in partial burning of the fuel....which looks just like a rich condition. This is one of the harder problems to diagnose on an outboard because you can't easily pressurize the cooling system to check for leaks as it is an "open to atmosphere" system.

On the other hand, BLUE SMOKE, which is an indication of engine oil being burned, can sometimes be seen as being white colored if it is very light and faint. If that is what you are seeing then I might consider that 'normal" on an engine with almost no time on it or one that has had the crankcase overfilled at some point. It is VERY important to NOT overfill the oil on these engines! AND, to store them in the upright position if at all possible. Until the outboard is properly broken in and has some accrued time on it (100 hours or so), faint, blue oil smoke is entirely normal as the piston rings have not fully "seated" in yet.

These are just some things to ponder as you seek a solution. DON'T GIVE UP ON THIS OUTBOARD! The Honda 20 D is the best outboard...pound for pound....in the WORLD!

And, as always...I can't stress enough how useful the official shop manual and Honda Marine Carb manual from HELM INC is for the guy doing his own repair.

Keep us posted as we are ALL interested in your SUCCESS at fixing your HONDA.

Well first let me say; Thank you very much for sharing your experiences and expertise with me on this matter, I am truly grateful. Does the Helm Carb Manual go into any more detail than the OEM Honda Marine Manual that I have??? I have the old carb to take apart and learn from it and thats my plan. Even if it proves to not be the carb I think with these motors its a good idea to know about them...seems to be their "achilles heel". I will be on vacation in mid July (staying home) so I won't be really working much on the motor until then, you guys have given me much to do though so I will be given you updates and probably asking more questions then. Thanks again guys.