BF2D carburetor adjustment

Had not run my 2 HP Honda in a few years. Unfortunately left gas in it and was unable to start, etc. Finally decided to buy a new carburetor after unable to clean adequately. With new from Honda carb installed engine starts fine but not idling very well plus cutting in and out as I advance throttle. I did change the spark plug also. Starts on first pull and does run after choke is in. I noticed what seems to be an adjustable screw. Can I tweak that a bit.
Bruce

Hi bbradb,
Looking at the parts diagram for the carburetor, there is an idle MIXTURE screw and an idle SPEED set screw.

Yes, you can use both to adjust the way the engine IDLES.

If you can get it warmed up, you can adjust the MIXTURE screw out 1/4 turn at a time and see if it smooths out while counting how many turns. If it does smooth out, continue to back it out until the engine begins to run slightly worse. Then, turn the set screw clockwise about 1/2 the turns that you counted.

This should put you near the sweet spot for idle mix.

Then you can use the other screw to adjust idle SPEED where you want it.

Try that and see if it makes an improvement. You can't hurt anything doing this.

The only thing I would caution you about is to never turn the mixture screw inward until it bottoms out and then over tighten it into the seat. Doing that could ruin the carburetor.

Let us know how you make out.

Good luck.

jgmo
Thanks for reply. I'm encouraged to hear from someone. Appreciate your info. Here's where I am at this time. Managed to get repair manual on-line for a few $. It's Honda so should be good. Printed off carb stuff. From that, pulled gas tank and checked fuel line and fuel filter. They both seem good and no trash in tank that I can see. I've replaced gas a couple times to make sure it is clean. Also saw both adjustment screws and went through process you described and also covered in manual. The idle mixture screw has some sort of limiter cap which only allows maybe an 8th of a turn. Saw some slight changes in idling by these adjustments. However, my real issue is what I would now describe as SURGING at higher RPMs. In other words, you can't get smooth constant increasing RPMs by twisting and holding throttle handle. Anyone have any idea where I can go with this. Remember, I have brand new Honda carb and new spark plug. Starts in one pull. Thanks all for reading.

Well, it does sound like a fuel issue but let me ask you a couple of questions.

Did the engine run great before you put it up without draining the carb? It in no way exhibited this symptom before you put it up with gas still in it?

If not, then I highly suspect that the new carb didn't get set up properly at Honda. Either that or it's possible that it isn't precisely the correct carb for your outboard. Before doing anything to the carb, you may simply want to exchange it if you can.

BUT...
If it was stored long term in a location where bugs or rodents could "set up shop" then it's possible that something critters did or left behind is, in some way, causing you headaches now.
Wasps are notorious for leaving mud "dobbs" inside crankcase vents, underneath flywheels and various other hard to see places.
And we all know how rodents love to chew wire insulation.

Getting back to the carb though....
The idle circuit does contribute fuel during high speed operation so, if it's too lean, it could cause some loss of performance.

However, the surging could be because the float height adjustment wasn't done correctly. Or, the inlet valve is sticking for some reason. I have flooded the float chamber with WD-40 by draining the fuel and, with the drain screw still open, sticking the spray straw in the drain and blasting away. WD-40 won't harm your engine UNLESS it pools up in the intake and hydro-locks the cylinder. So, when "flushing" like this, pull the spark plug and spin the engine a bit for safety's sake. Sometimes this flush trick works. Most times not.
You will have to take the float chamber off to check/adjust the float setting if you suspect that is the problem.

Yes, the limiter cap is "glued" to the head of the idle mixture screw with Loc-Tite. It can be easily removed by applying heat from a soldering iron. The cap is usually destroyed while doing removal this way. You can purchase a new one though if you want it on there. You're "technically" not supposed to do this but I have yet to see the Limiter Police come for anyone.



I hate to tell you that I've purchased carburetor float chambers directly from Honda Genuine Parts when I worked for a dealer that had sand from the casting mold still in them. It is rare but it happens.

There are numbers and letters on the carburetor that can help identify them. Make sure that the ID on your new carb matches your old one. If not, you'll need to find out why.

Double check the correct part number for the replacement carb according to frame, serial numbers and year model. Verify that is the part number that you were shipped.

Can't think of anything else at the moment but I'll get back to you if I think of something else that you can try.

Good luck.

jgmo,
Excellent feedback my friend. You've worked on a few of these. Honestly not sure if outboard was running like a top last time I had it out. I purchased it used and I'm thinking I may have felt it was iffy. I'm not really a boater. Bought this and a little boat on a whim and have hardly used. Trying to sell now. Maybe I bought a boat anchor and didn't know it.

I will explore all of your points tomorrow. They all make sense. Hopefully I chose correct carb. Sort of doubt I can return at this point unless I can demonstrate that I ordered correct one and they sent wrong one. I will go over serial numbers tomorrow to verify. Pretty sure I was careful there. It looks identical anyway. I still have original one so I will check again.

Did wonder about float. Since I have repair manual I can check those specs. I will definitely get rid of limiter cap on idle jet and fiddle with that. I see some info in manual on recommended turns for that. It's for sure not idling right even after following manual procedure. I will also poke around and see if I can determine if somethings plugged. There is some kind of breather tube coming out of engine and maybe fed to air cleaner that I will check. I will leave off what looks like the air filter piece and try running for one thing. It doesn't look dirty but cant really get it apart to tell that I could see. Also thought about leaving the so called fuel filter off. That was the strangest filter I have ever seen but it appeared to be clear.

Thanks alot for great tips. Curious where you live? I'm in SC. I'll keep you in the loop.

Was trying to figure out if I could speak to a Honda tech but couldn't come up with a phone number. Hate to take to a shop cause it will cost me a couple hundred for sure. Bye bye getting my money out of this. lol

Bbradb,

I'm in SC too!
Southern California that is.;>)

Yes! That tube coming out of engine and going to air inlet is the crankcase ventilation. If it's partially blocked by an old dauber's nest, it could raise crankcase pressure. That might cause the engine to run at less than optimum.

Like I already said, I've seen brand new parts in sealed bags that have problems.
Like a guy I know that's waaay smarter than I once told me:

"NEW don't mean nuthin' except Never Ever Worked"!

And I have found that to be true many times.

Hopefully you'll be able to dial it in by adjusting the mixture a tad.

Good luck!

The latest. I'm close to considering purchasing another carb. Verified I have the correct one. Still strong hesitation occurring with increased RPMS. Idling seems reasonable. Tried popping the top of idle adjust screw to give more room for tweaking. That was a mistake. Cap popped off along with spring. No slot underneath and no way to reinstall. Again though idle is reasonable so I'm not worried about that. Checked float and no adjust possible. Seems to always have fuel present in bowl so I'm discounting that at the moment. Guess I'm thinking may have bad carb. I will talk with supplier and see what they say. Returns of used stuff not allowed it looks like. Maybe they will discount another one?

As the teen girls say....eeeww!

I take it you didn't use a soldering iron to melt the glue?
No matter...
Those screws were designed to break off if forced. You can buy a new screw
I wouldn't buy a new carb just yet.
If you look inside the screw cavity and see a smooth, flat, round piece of metal in there, that is the actual top of the mixture screw
.
That screw can be removed by using the sharp tip of a seal pick (set of four $2.99 at Harbor Freight). Push the tip of the pick into the screw head near the outer edge and push to the left to get the screw turning. Keep doing this FOREVER....jus kidding....but it will be a while!

It could take 20 minutes or longer doing this as the pick tip will slip often. You have to hold your tongue just right...if you get my drift.

Don't expect the screw to jump out when the threads are disengaged. There imay be a small oring under the head that acts as a sort of "soft lock", keeping the screw trapped. Although, I don't see that oring in the parts breakdown.

Once you are confident that you have turned that sucker 100 times and the threads MUST be disengaged.....turn it 25 more times! Yeah, it's like that.

THEN, start working the pick tip, or mini screwdriver or sail needle or...anything you can....under the edge of the screw head to pry it up. That little oring under there can stubbornly
hold on and try to defeat you but don't give up...it DOES come out....eventually.

Hopefully, you saved your old carb and can replace the screw from that. Just remember to use heat to defeat the glue (Loc-Tite) and keep in mind that the "false head" of the screw will pop off if forced.

OR...now that the original screw is out, you can file or use a Dremel wheel to make a slot in the flat for a mini screwdriver and you can use the screw that way. I've done it many times on rental motors after a customer fiddled with it.

And...they sell for $9.08 on boats.net
$60.00 less than a new carburetor.

I do have old carb so will take your advice and change over the idle screw (first removing cap with Soldering iron). Honestly though, that's not why I am considering new carb. Idle is pretty good right now. It's the hesitation at higher RPMs thats bothering me. Can't steadily increase throttle. Very definite hesitation showing up quickly. I called it surge before but it's hesitation. Wonder if bad carb like you have experienced.

Well...it could still be the carb but it could be something else.
Like:

Valve adjustment maybe....

You have the manual...look at the troubleshooting section for ideas about what to check.

Check the valve adjustment. That could cause hesitation.

Play with the idle mixture....the idle circuit DOES play a small role when throttle is fully open.

Ensure that the choke is FULLY open when the engine is warm. A slightly closed choke blade could cause a rich condition and, that too, could affect top end performance.

I don't know how difficult it is to get to the centrifugal clutch but I would want to see how everything in there looked and moved if this were happening to me. A sticking clutch mechanism might FEEL like hesitation.

I can't tell you what it is but those are a couple more things to think about.

bbradb said:

I do have old carb so will take your advice and change over the idle screw (first removing cap with Soldering iron). Honestly though, that's not why I am considering new carb. Idle is pretty good right now. It's the hesitation at higher RPMs thats bothering me. Can't steadily increase throttle. Very definite hesitation showing up quickly. I called it surge before but it's hesitation. Wonder if bad carb like you have experienced.

Click to expand...

Let me know after you figured out what is wrong with the engine. I have similar issue. The engine would idle fine, but hesitate then stall at initial rev around 2000 rpm; seems like fuel is flooding the carb at the initial acceleration. I adjusted the idle and fuel mixture screw, but can't seem to find the sweet spot. To get around the issue for now, I would rev up slightly and keep constant rpm below the hesitation point for 10 sec; engine would accelerate then back to normal. After the surge, the engine is running fine at all RPMs. Not sure what it is but it a quick fix for me right now. I have ordered a new carb to see if it will fix the problem.

jgmo,
Responding to your last post. Decided to NOT order another carb. Thanks for your advice. Thinking about it, This is Honda and that means alot to me having had a number of their cars and other engines including generators, pressure washers, etc. I would be so irritated to install another new carb and have the same issue so I'll give them benefit of doubt for now. They had to have had some kind of jig to test and setup the carb before it went out the door. Why would it be bad out of the box? I can fix the messed up idle screw thanks to your help. I'm convinced fuel flow is good. I can empty tank by opening drain in bottom of float bowl pretty quickly.

Your idea of valve issues makes sense. I will start by checking adjustment on valves. Hmmm, if they have been out of adjustment for some time could valves be burned? Hopefully will be able to adjust idle as well. I believe choke opening on choke is good.

I'm away for the weekend at our place in Blue Ridge Mts. Good to get out for a change and we are really isolated on top of this mt. I've been stressing over this engine and other stuff going on in our crazy world. Thanks again for your responses. Always get good tips from you. I hate when some folks on these forums want to have all the answers. With you I feel like you are in the shop with me, saying "hey let's try this?". By the way, I'm 76 but been messing with motors occasionally since my dad bought me an old B & S horizontal shaft engine when I was about 12. Can't tell you how many times I tore that thing down and put back together.

Just watch this thread and you will see the outcome. I'm hoping I won't be dumping this motor but I'm not giving up yet. My goal is to sell the motor and the boat that goes with it but I can't do it in good conscience until I get to the bottom of this issue. I actually have a buyer but I told him that I need to solve this one.

Check that your oil level is correct, it must sit in the middle of the sight glass or slightly lower, if over full at all it will affect the overall running quality

Bradb

Thanks for the compliment. I sure as heck don't know it all! My kids can tell you that! I'm right up there with you age wise and still can't believe I made it this long!

Ian makes a good point about overfilling with oil. Not great for any engine but maybe this little one is especially sensitive?

I love your attitude about passing a problem on. I will not sell anything like that unless it goes at a bargain with full disclosure. "Treat others as you would have them treat you"...
.... is goodness and light and positive karma and, well, all that.


Have a GLORIOUS time in the highland!

One thing to do with any internal combustion motor that has been sitting around is a dose of sea foam in the gas. Our 91 octane is ethanol free and I use it with a dose of sea foam in my outboard, mowers, chain saw, etc. I use it in my 409 and my old Holley 2 barrel Dakota needed it once a year. It cleans out varnish etc in carbs and in the valves. Cheap and can’t hurt, I’ve been using it for 20 years and haven’t touched a carb since I started doing this.

Add to your gas tank and run engine at fast idle for 5 minutes at least or even better, launch and use it on the boat and see if anything changes.