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Honda BF20D Hard Starting

T

tcoop

New member
Hi All, I am new to the forum but I have have read many of the older threads that mentioned BF20D's.

The engine has sat with gas in it from the previous owner for the last 3 years and has been difficult to start all along. So I wanted to get it running correctly so I embarked on cleaning the carburetor. I replaced all the O-rings and gaskets during the cleaning process. The only thing that seemed odd to me was the brass tube that is by the accelerator pump didn't seem to be drilled. I can only get a small wire to enter 1/8". I convinced myself that the tube is used on another model so I reassembled it all and still have a difficult time starting. For 5-10 minutes it will fire immediately and then die within a second or two. Once warmed up, it seems to run fine and starts first key turn. The carb is now on the bench again and I discovered I tore the Fuel Enrichment O-ring, I have a replacement now. Working to remove clog but not making traction, I left just the tube soaking overnight with the rest of the body dry. Still feels like it wasn't drilled.

Other things done: Using E0 gas, drained fuel chamber, replaced fuel filter, replace water separator, replaced plugs, all jets removed cleaned, inspected and reinserted, all other passages cleaned(I think)

I am hoping I am headed down the right path with unclogging the brass tube? Looking for ideas or suggestions so I don't ruin the tube/body.

Thanks
Tim
 
tcoop said:
I am hoping I am headed down the right path with unclogging the brass tube? Looking for ideas or suggestions so I don't ruin the tube/body. Thanks Tim
Click to expand...
That jet you're trying to clear in the brass tube is about the size of a whisker hair. I use a single strand of a stainless steel wire cleaning brush. The small dollar variety. Hopefully your's isn't damaged beyond the point where it needs to be replaced.
 
That tube is called the "primary fuel jet" tube. It feeds the two primary (or "high speed") fuel orifices that you can see at the top of the carb throat when you look in the engine end and open the throttle plate. You will know that it's clear when you spray cleaner into the tube end and it sprays out of those two orifices. The Carburetion Manual references cleaning the tube with the "correct size jet cleaner" but doesn't bother to list what that size might be. At least not that I can find. So Alan's "diameter of a hair" is the best specification that I know of.

The problem with what you describe though is hard starting and I wouldn't think that the primary (high speed) tube being plugged would necessarily cause that. Although...these carb's individual circuits work together during most operating parameters so I could be wrong about that. I do know that the accelerator pump injection tube being plugged can cause hard starts so anything is possible to be sure.

Have you thoroughly cleared the accelerator pump feed tunnel in the bottom of the float chamber and checked that the accelerator pump tube injection nozzle is COMPLETELY clear? Charge the accelerator tube with spray cleaner and you should see a minimum 6 to 8 foot stream out the rear of the carb from the pump nozzle with the throttle plate held fully open. If not, backflush the nozzle using the spray straw. It can take many tries to clear the nozzle.

The main air jet and slow air jet passages are two holes sort of stacked one above the other just above the entrance to the carb throat. Don't neglect to spray the heck out of those because that's where critters will take up living on a long stored unit. Same goes for the atmospheric breathers. Spray them out well.

Brass pickup tube for the SE valve should be sprayed out well too on one that's been sitting with old fuel.

If you haven't removed the idle mixture screw and hosed out the idle passage backwards AND forwards....several times....I would urge you to do so. As I said before, all of the circuits work together and it is especially true that the idle circuit delivers during idle, transition AND high speed operation.

Don't try to reuse the small orings for the jet set and idle valve. Have replacements on hand and treat them with kid gloves during installation.

As you may know, the idle screw "false head" can be broken off during removal of the limiter cap but it won't break if you're careful and take care when heating up the cap. I've even reused broken ones by cutting a new screwdriver slot. But they aren't very expensive to just replace and give your work that "finished" look with a shiny new limiter cap glued on.

I also recommend removing and completely emptying the black "fuel chamber" that's mounted on the engine oil dipstick tube. Those WILL collect water and should be shaken dry every season. Using WD-40 can make removal and installation much easier. Do not get "frisky" with the dipstick tube. If you break it off by accident you will be in trouble.

Good luck and let us know how it's coming along.
 
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WOW thank you for the in-depth reply. I have done about half of the things listed if I understand correctly. I will need to complete the tear down again. I wasn't that thorough with the accelerator pump. More to come I hope to spend some time this afternoon on it.

On the primary fuel jet tube, the hole seems large at the bottom of the tube compared to other jets. Does it get smaller as it goes up the tube?

Thanks
Tim
 
Yes, the tube should "neck down" about 1/8" or so above the opening if I remember right. It's been a few years since I cleaned one.

The way it works is that atmospheric pressure is trying to push fuel up the tube. When the throttle opens a given amount the air moving through the carb throat helps pull the fuel up and through the two orifices.

The tube gets smaller above the intake to take advantage of the Bernoulli effect so that it speeds up the flow. It is effectively a "jet" in that sense and that's why it's important to not enlarge or distort the passage.

I have always been able to hose the tube clean with carb spray. But I start by bending the end of the straw and putting it against the orifice holes in a backflushing action. I do this also with the accelerator pump nozzle and tube. I've never had one that I couldn't clear that way but I realize I've probably just been lucky. I am stubborn and will spend a lot of time flushing and backflushing to get a tube clear. It can take a couple of cans of carb spray to clean out a clogged tube but it works for me.

Other guys use sonic cleaners and wire but I've never had a great deal of luck with sonic cleaners (I have two) and I'm paranoid about breaking a wire off inside a nozzle.
 
Today's update:

Primary fuel jet still won't pass cleaner through. I haven't given up yet but getting an all new carb is sounding better after each spray of the cleaner. See responses to questions below.

Have you thoroughly cleared the accelerator pump feed tunnel in the bottom of the float chamber and checked that the accelerator pump tube injection nozzle is COMPLETELY clear?
TC: I thought I had done this the first time through but last night I had my doubts it was clear. After soaking overnight it is clear now.
Charge the accelerator tube with spray cleaner and you should see a minimum 6 to 8 foot stream out the rear of the carb from the pump nozzle with the throttle plate held fully open. If not, backflush the nozzle using the spray straw. It can take many tries to clear the nozzle.
TC: I am seeing a spray 6-8 feet.

The main air jet and slow air jet passages are two holes sort of stacked one above the other just above the entrance to the carb throat. Don't neglect to spray the heck out of those because that's where critters will take up living on a long stored unit. Same goes for the atmospheric breathers. Spray them out well.
TC: Sprayed all with the bent and angled straw.

Brass pickup tube for the SE valve should be sprayed out well too on one that's been sitting with old fuel.
TC: Completed

If you haven't removed the idle mixture screw and hosed out the idle passage backwards AND forwards....several times....I would urge you to do so. As I said before, all of the circuits work together and it is especially true that the idle circuit delivers during idle, transition AND high speed operation.
TC: Screw removed and thoroughly flushed

Don't try to reuse the small orings for the jet set and idle valve. Have replacements on hand and treat them with kid gloves during installation.
TC: Have new o-rings

As you may know, the idle screw "false head" can be broken off during removal of the limiter cap but it won't break if you're careful and take care when heating up the cap. I've even reused broken ones by cutting a new screwdriver slot. But they aren't very expensive to just replace and give your work that "finished" look with a shiny new limiter cap glued on.
TC: the cap had been removed before I got the engine.

I also recommend removing and completely emptying the black "fuel chamber" that's mounted on the engine oil dipstick tube. Those WILL collect water and should be shaken dry every season. Using WD-40 can make removal and installation much easier. Do not get "frisky" with the dipstick tube. If you break it off by accident you will be in trouble.
TC: Completed
 
Well....
I agree with you about cutting your losses and getting a new carb. They are relatively inexpensive and can often be the best way to go. There comes a point where your time and the cost of carb spray makes it the smartest move.

It's too bad though because you seem to have checked all the boxes except that tube. I have never had one that plugged before but I have tried helping others that have had major problems with getting them clear.

You could install the new carb and continue to try and clear the tube. If you succeed you will probably have a spare carb to put in a baggie. If you don't clear it the old one is still valuable because, if you break a piece of the plastic linkage or the return spring on the replacement it can be a donor for those parts since you can't buy them separately. So, there is a small bit of sunshine.

If this happened to me I would probably try drilling it out with a very small twist drill in a hand powered mandrel chuck. The problem with doing that is....what size drill???
All I know about that is "the size of a hair" as Alan said. But, if it can't be cleaned any other way, there's not much that keeps me from taking a shot at it.

Sorry I don't have the magic bullet for this one.

Good luck
 
So, I put a couple more hours into cleaning the carb without success. I ordered a new carb bolted it in turned the key and it started and stayed running until I turned it off. I had never had that happen before so I am quite pleased how it is running. Since I owned it, it has never started so easy.

I did think about drilling the port out but I would have had to get a size 80 drill not knowing what size it should have been. Then the worry about where would the shavings go. I do have a a lot of spare parts now but hope I won't need them for a long while.

JGMO and Allen thank you for the input. I really appreciate your time and input.
 
Glad to hear you won this battle! Probably goes without saying this is why guys that have been messing with this stuff for a while nearly always make a big point of draining the carbs if it's going to be sitting for more than a couple of days, running some sort of fuel conditioner/stabilizer, or BOTH!
 
Congratulations on pulling the trigger and getting the job done. The BF20D is one of the finest outboards made. That's why I call them "for life" machines. Other than that pesky carb they are very rugged and reliable for the most part.

Alan is right and we do plenty of preaching about keeping the Honda carbs drained to prevent what's happened to yours.

But...they are machines and they do break. Despite the best of efforts they can find ways to let us down and cost us money. That's why I've always kept an anchor, line and oars on my boats. Although, a vfh radio or cell phone will do in a pinch.

Thank you for the update and best of luck.
 
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