BF 20 - hard cold starting and engine running lean

Problems started late last fall. Engine stalled during cruise and wouldn't start. Cleaned the carburetor, changed rge spark plugs and it worked well for 15 minutes and stalled, wouldn't start again.

Next spring I started a closer cleaning/inspection of the carburetor. Reassembled and could only get it running by spraying gas into the carb. Eventually, took the carb to the local Honda dealer for a professional cleaning and inspection. Still wouldn't run

Emptied the fuel chamber; fuel lines, changed fuel filter, spark plugs but still needed gas sprayed into the carb continously for it to start and continue running

Finally noticed something looked weird in the bottom if my tank and realized there was about 30% water in my fuel!!

After finally emptying all the fuel from the tank, hoses, fuel filter, fuel chamber I managed to get it started(after about 20 pulls) and it ran perfectly once started .

Only problem is that it will no longer start with the choke and it takes upwards of thirty pulls to get it started. Even after it just fires up, if I try to open the choke a tiny bit the engine starts to stumble and stall.

So here's my three problems.:
1. Very hard to start when cold.
2. Using the choke only makes it worse.
3. Spark plugs have a whitish electrode(curved metal arm) which suggests that it is running lean and maybe fuel starved. HOWEVER; once started, it runs well, all day and hot starts always on first pull.

The motor was bought in 2011 so has about 9 seasons of use for the fuel hose and primer bulb(never been changed). The bulb pumps firm but never completely fills rhe small fuel filter before the carburetor Is this normal? I thought it should be completely full of fuel to prevent any priming problems...??? The hose and primer bulb looks fine but could this cause the hard cold starting and lean running???

Please do offer an advice or experience in this matter. It will be most appreciated!

Hi,
Frustrating problem I know.

First off, the little, clear, inline fuel filter will always look sort of "half full". It never looks full of fuel. Perfectly normal.

I think you've proven it's a fuel starvation issue since you can spray fuel in the carb and get it running.

And, since it runs ok after fighting to get it cold started, I think the fuel pump is probably ok.

Curious as to how you got 30% water in your fuel? The only time I've ever seen that is when the tank is left in the rain with the vent open.

Have you drained the fuel chamber again? It wouldn't hurt to try as it will trap any moisture in the fuel and store it.

Having said that, I think that you will need to either replace the carburetor (easiest solution) or clean it properly. All that water, especially if it was rain water, will have left mineral deposits in critical passageways and she's never going to run correctly until those are clear.

For around 1/2 the cost of a new carb, you could instead purchase the HONDA MARINE CARBURETION MANUAL and do a proper cleaning yourself. I'm not one to trust the knowledge and skill of most outboard shops, including "authorized" Honda dealers. They simply don't know what they're doing when it comes to servicing these little, precision and finicky carburetors.

I suspect that your problem lies mainly in the accelerator pump circuit. Specifically in the spray nozzle tube feed portion of that circuit. That circuit, when even slightly restricted, will cause all sorts of starting and running issues.

But it could just as easily be the float chamber feed, the low speed air bleed circuit or the idle and intermediate circuit orifices. That's why a thorough going through is the only way to be confident the thing is going to work correctly when bolted back on.

One other thing I would do here is to replace the plugs with new NGK's. There's a good possibility that one or both have been damaged from running lean and hot like you describe.

These engines run surprisingly smooth on only one cylinder and that can obviously be misleading when troubleshooting "runability" problems.

jgmo said:

Hi,
Frustrating problem I know.

First off, the little, clear, inline fuel filter will always look sort of "half full". It never looks full of fuel. Perfectly normal.

I think you've proven it's a fuel starvation issue since you can spray fuel in the carb and get it running.

And, since it runs ok after fighting to get it cold started, I think the fuel pump is probably ok.

Curious as to how you got 30% water in your fuel? The only time I've ever seen that is when the tank is left in the rain with the vent open.

Have you drained the fuel chamber again? It wouldn't hurt to try as it will trap any moisture in the fuel and store it.

Having said that, I think that you will need to either replace the carburetor (easiest solution) or clean it properly. All that water, especially if it was rain water, will have left mineral deposits in critical passageways and she's never going to run correctly until those are clear.

For around 1/2 the cost of a new carb, you could instead purchase the HONDA MARINE CARBURETION MANUAL and do a proper cleaning yourself. I'm not one to trust the knowledge and skill of most outboard shops, including "authorized" Honda dealers. They simply don't know what they're doing when it comes to servicing these little, precision and finicky carburetors.

I suspect that your problem lies mainly in the accelerator pump circuit. Specifically in the spray nozzle tube feed portion of that circuit. That circuit, when even slightly restricted, will cause all sorts of starting and running issues.

But it could just as easily be the float chamber feed, the low speed air bleed circuit or the idle and intermediate circuit orifices. That's why a thorough going through is the only way to be confident the thing is going to work correctly when bolted back on.

One other thing I would do here is to replace the plugs with new NGK's. There's a good possibility that one or both have been damaged from running lean and hot like you describe.

These engines run surprisingly smooth on only one cylinder and that can obviously be misleading when troubleshooting "runability" problems.

Click to expand...

Hey, thanks so much for the thorough response. Much appreciated!

I was surprised how much water was in the tank also. I do leave my portable fuel tank in the bottom of my boat exposed to the elements so it is possible a little rain water got through the vent. However the problems started all at once and I think it was from a bad tank of mid grade gasoline. Must have been the bottom of the barrel so to say!

Yes, I did thoroughly drain the fuel chamber again as well as all other fuel components. I'll try to attach a photo of my contaminated gasoline if I can.

I swear I removed the carburetor at least 4 times to clean, disassemble and inspect. I used laquer thinner and carburetor cleaner(spray bottle). Yes, I removed the plastic and rubber parts. And like you, I have very little trust for most marine mechanics and their intimate knowledge of how to properly service carburetors. Nonetheless, I did let them clean it(they use Gunk) for $100....

I even changed the carburetor bowl because I had lost a tiny retaining clip in the accelerator pump bore the first time I cleaned it. The float and needle valve looked perfect as did the main jets.

Changed the spark plugs a couple times and even disconnected the emergency stop circuit to eliminate that problem.

What really bugs me is that logically the choke should richen the mixture but it doesn't help. It feels like it's not getting enough fuel to start but the choke makes it worse. But when it does finally start, if I pull on the choke knob just a little it wants to stall. When it's warm it starts easily.

It used to start first pull with the choke pulled out and required it for a few minutes until it warmed up a little.

So basically, it just seems like a carburetor blockage somewhere to you? Should I buy an ultrasonic parts cleaner? So the fuel hose/primer bulb is a non-issue here in your opinion?

Thanks!

I wouldn't bother with the ultrasonic unless you can afford a really good one. The "bargain brand" cleaners just don't work well.

I doubt the hose and primer bulb are causing this but who knows? They are items that do need to be replaced every few years so I could be wrong.

I'm sticking with it's the carb and it has blockage. Most likely in the accelerator pump circuit.
Some cleaners can be too harsh for these carbs and I wouldn't recommend submerging one in the old, conventional carb solutions.

Hondadude used to admonish me about even using spray carb cleaner. He recommended brake Kleen instead. But, then, he was in Ohio and I'm in California. We're not allowed to have Volitile Organic Compounds or even BB guns out here because we'll put our eyes out!

Let me ask you these questions:

Did you remove and clean and magnify inspect the low speed jet (jet set)? If so, did you use a new oring at the top of the tube? Did you see any cracks? Inside of tube COMPLETELY clean?

Did you blow out the low speed and high speed air bleed passages?

Did you backflush, foreflush and backflush again the idle, transition and high speed orifices with the idle mixture screw and jet-set removed?

Did you backflush, foreflush, backflush and foreflush the accelerator pump orifice and feed tube until a minimum 6 ft.stream of cleaner would shoot out the back of the carb throat with the throttle plate linkage propped wide open?

Your understanding of these items and how you answer those questions is pretty important as to whether or not you did any effective cleaning when you had it off.

Hello @jgmo. Hey, sorry for not getting back to you after your last message to me. I feel bad about it. Really appreciate your help.

Figured I'd let you know how things have been going with my BF20 since we last chatted.

I went ahead and removed the carburetor again. Removed all screws, jets, emulsion tube, bowl, slow jet and o-ring. Removed rubber parts and sprayed a full can Brake Kleen and half a can of carb cleaner down all holes and passageways. had a real nice spray(8 feet) coming out the accelerator pump nozzle in the carb bore. Pretty confident that everything was pretty good(again!). The only thing that didn't satisfy me was trying to clean out the long brass tube jutting down from the carb beside the accelerator pump. Finally managed to see some cleaner come through one of the orifices on top of carb. Just seemed a little weak but couldn't do any better so proceeded to blow out all holes with compressed air and re-assembled with new valve needle, emulsion tube, slow jet tube and new o-ring.

Cleaned out all fuel system components and installed new spark plugs.

Managed to get it started after about 15 pulls but could tell right away that the said problem was still there. went fishing the next day and took me about 10 minutes of tortuous pulling to get it started. Still won't fire with choke(manual) engaged.

But I noticed something when it started, I had twisted the throttle grip a couple of times before I pulled the cord. So I just came back inside after some testing.
Results:
-ignition produces a nice strong spark
-will start with choke disengaged eventually
-will NOT fire if choke is engaged UNLESS I twist the throttle a couple of times before pulling in which case it will stutter and die after a second or two.
-after starting, the motor idles nicely, accelerates well with no hesitation, has solid high speed performance and hot starts on first pull everytime.
-spark plug ground straps look nice, maybe a little lean? Light grey colouration and insulator tip clean. Maybe I'm just used to my oil burning snowmobiles and their nice brown ground straps...


Questions:
-I assume that by twisting the throttle a couple times the accelerator pump blasts a couple of streams of fuel into the carb throat, giving it enough fuel to fire for a couple seconds until it is depleted?
-If this is true, is the problem only related to the fuel enrichment circuit and maybe that feeder tube I was telling you about?
-If this is blocked is it logical that the engine will NOT get starting fuel if choke is engaged? Seems like the choke LEANS out the engine?
-assuming this is true, could I bother you, once again, for a little advice?

You wouldn't have a diagram of exactly what holes to blow in/block and where cleaner should come through to clean out this circuit, would you?

I probably spent about half the price of a new carburetor in little parts but haven't fixed anything yet and am willing to give it one last shot before I have to spend $450CAD for a new one.

Like you've said before, I want to be confident that it will work if I put it on one more time!!!

Thanks.

Hi JGaz,

Well, these little carbs have given me and many others plenty to grind our teeth over through the years. I do my level best to try to understand the problem and come up with a solution but trying to diagnose blind and through a keyboard has me batting at less than 400 as they say.

The brass tube you're referring to sounds like it is the high speed jet tube. They can get badly plugged up and it sounds as if yours might need mechanical cleaning. That can be a VERY tricky chore as accidentally enlarging the jet could render the carb junk. I've always been able to clean them out with flushing and back flushing over and over again. But there was one guy that I helped here that had to get "physical" with his using very small diameter wire along with flushing to dislodge the clog. I suspect that there has got to be a jeweler's drill that might work for cleaning the tube but I certainly don't have one. The Carburetion manual barely mentions that jet and there is reference as to what size that passage should be.

However, I'm not at all convinced that the high speed jet is the cause of your cold start issue.

You are correct that twisting the throttle a couple of times should have the accelerator pump squirting fuel into the carb throat and enriching the mixture some but, while it may help a little, it's totally unnecessary with a properly operating carb. And, if you still have passages that are a bit clogged, it will probably not help at all as they will likely cause the condition to worsen as to passages "fill in" again.

The main thing you need to do to understand "what to plug up when spraying " is to remove the idle mixture screw and the "jet set" tube. When you flush in the hole that the jet set pushes into at the top of the carb, the fluid will come from the front mounting flange (slow speed and high speed air jets) the idle mixture screw orifice and the small orifices at the top of the carb throat in the rear.

I use my finger tips, including thumb, to block two of the passages as I spray if possible.

For example, if I shoot fluid into the idle mixture hole, I try to plug the front flange holes and the jet set hole. This puts most of the spray force going out the tiny drillings at the top of the carb throat. I do this with the throttle plate linkage propped open so I can see what's coming out of those little holes. It turns into a bit of contortionism to do this.

When spraying into the jet set hole, I block first the air jets at the front flange and then the idle mixture cavity next to get maximum flow out one way and then the other.

Then you put the spray tube into the front flange holes and block the jet set hole. This maximizes flow out of the idle mixture hole and the tiny carb throat passages. While still spraying into the front flange holes, block the jet set hole and the idle mixture cavity to force maximum flow out the carb throat orifices by themselves.

You then take that spray tube and carefully try to cover each of those small carb throat holes and give them a burst of fluid to backflush each passage.

I have had to do this several times, back and forth, to clean very plugged up Honda carbs. It's a lot of messy work and can take much time and spray cleaner to get a bad one working properly again.

I suspect that your idle mixture passage and/or orifice may still be dirty. But I have learned that all the circuits in these carbs are somewhat dependent on each other flowing correctly for the carb to "breathe" and there's no short cutting the cleaning process I've outlined here.

Believe me, I've bolted many of these carbs on only to find myself taking them back off to try the cleaning "dance" again. But, I've never had one that I couldn't get working properly in the long run. Maybe I've just been lucky???

I wish you luck and that's for sure!

Hold on! I am an idiot! This is very embarrassing to admit but I just realized I've been neglecting the "choke"!

Which isn't a "choke" at all!

It's a manual fuel enrichment valve! That HAS to be your problem!

My poor excuse for missing this is that ALL the BF20D outboards I've worked on are electric start, including the one I own. But I'm completely familiar with the cable actuated enrichment valve from other models.

That cable actuator is NOT the best thing Honda has ever hung on their outboards. As a matter of fact, I have it filed under my personal nomenclature file of "junk items" that fail frequently.

You will need to remove the carb to unscrew the actuator. If you inspect it closely, you will probably find a crack in the cable sheath. If the sheath is cracked it won't support the full "throw" or movement of the cable and that will affect your ability to enrich the mix for cold start.

I should have caught this MUCH earlier to save your poor shoulders! But I've been out of the biz for some time and when CHOKE is mentioned my old, feeble brain reverts to the old "trap door" chokes of my time. I apologize for not realizing this sooner!

Yes, you will find your problem with that cable or enrichment valve at the end of it.
I remember trying to repair these but with little success. I ultimately found that replacing the valve AND the cable together the most reliable way to go.

The valve set is made of soft plastic and the threads for screwing it to the carburetor body are very delicate. They will easily strip if over-tightened. It's also easily cross-threaded. So use care when replacing it.

I hope this FINALLY brings your ordeal to an end!

Hey jgmo! No worries about missing the choke part.

I have inspected this item. Cable looks nice and when actuated(pull on choke lever), the piston-like valve rises accordingly. I will have to look closer for any cracks like you say. Yes the plastic threads are fragile and in my last attempt to fix my motor I changed the plastic threaded part and the little piston or valve with new Honds parts and no change in cold starting.

So basically you are saying that it doesn't pull the valve up high enough when I engage the choke? Might be a threaded adjuster behind choke knob to remove slack? Hmmm...

Well, I don't recall an "adjustment" but, yes, it's a possibility.

The enrichment passage might be clogged but I don't recall ever seeing that either.

My recollection is that these things were problematic unless I replaced cable and valve as a "set".

But I didn't do more than a handful so that experience level isn't all that deep.

Make sure the oring under the valve is in good shape. Air entering there could effect it's performance.

Keep digging in that area and I'm confident you'll find your issue..

Hi JGaz,
I just thought of something that might be causing your problem. In the bottom of the fuel chamber (float bowl) are three passageways. One is for the drain screw, one is the fuel feed to the accelerator pump chamber and the third is the fuel feed for the SE valve (enrichment) dip tube.
You may have a blockage in that passage causing the enrichment system to be starved for fuel.

I have never seen that passage plugged up but I have had to clean out the feed passage to the accelerator pump on many carb bowls I've cleaned. I've had to use small gauge wire to "dig" the crud out of the little accelerator pump "feed tunnels" as they will get packed in pretty solid sometimes.

This is kind of a long shot but something that came to me as I was wondering how you might be getting on with trying to sort out your problem.

As always,

Good luck.