bf100 honda 10hp wont idle......plz help

Bought a older honda motor from a guy its a bf 100 serial number is 1202272, be nice to no the year but i do not. This motor looks like mint condition but wasnt properly put away to rest for a few yrs. I am having a hard time getting this motor to idle, runs the best at higher rpms but however not perfect, sometimes it will run for 5 mins at a high rpm when i turn idle screw in a ways and some times it will only run for a min then die like u shut the gas off. it however wll not idle correctly on its own, just wants to die, if u keep choke half way out it idles the lowest and will stay running if u kinda help it with throttle every 10 to 15 secs.

Things i have done to this motor are

bran new fuel pump (complete assembly)
bran new fuel linesand inlne fuel filter between pump and carb
all parts inside carb are new...also new gasket between carb and intake
new primer ball ,hose ,tank, connectors
all new vacuum hoses

carburator soaked in seafoam for two days( was gummy inside when first took it apart)
i tried for about 3 hrs and cannot get this motor to idle properly
starts usually one or two pulls with choke on
doesnt seem to change how it runs from temp of motor
tried gravity feeding the gas into carb and still ran the same
ive taken carb apart a half dozen times cleanin it blowin out ports and what not
i did notice however when replaceing the larger vacuum lines that ther was alot off chunks of rubber inside them from th hose being so bad.(wondern if it sucked a piece inside the motor somehow maybe?) the lines where in bad shape like i said so i replaced them. This motor just looks like new doesnt look like it has aton of hrs at all just will not idle! also water is comming outa the pisser very nicely. Iv'e trie turnin the air fuel screw in and out in every spot lol, read that it should be bottomed out then uscrew 2 1/4 turns approx. when i cleaned carbs all 4 times i ran a thi piece if speaker wire threw all the little tiny holes on the car, ever singl on, it just acts like a vacuum leak i checked all connections and all areas with a can of wd-40 and cannot ind ay kind of vacm leak. i also took apart the breather valve assembly for the vacuum, cleaned it out. ther wer a few chunks off rubber hose in ther. i even blew just by mouth not air compressor into all vacuum line to make sure somethin wasnt plugged up (air went thew all spots just fine.


someone plz help if they would have any kinda idea.....thank u vey much

I bought 2 older Honda 10 hp motors from an owner that could not get them to idle properly .-----Nor could he find a shop to properly clean the carburetors.--------Had both idling properly after cleaning the wee jets in carburetors.--------So you say you have to use choke to keep it running.--That clearly indicates that something was missed in the cleaning of carburetor !-------Take your time and go over it again.

I agree with Racerone...

The idle mixture screw should be 2 1/4 turns, like you said, unless it has contact breakers with serial numbers in the range 1000004 to 1199999 or a CDI type engine with serial numbers between 1200001 and later. Then it should be 1 3/4 turns out.

Also, be sure to remove part #7 (slow speed jet) and clean it and clean the passage that it goes into. You should be able to shoot brake cleaner into that hole and it should come out the pin sized holes at the top rear of throat of the carburetor. If you can not get flow there, it will not idle. http://www.boats.net/parts/search/Honda/Outboard%20Engine/0/BF100D%20LA%20/CARBURETOR%20%2B%20AIR%20GUIDE/parts.html

Also be sure to remove part #s 9 and 20 and make sure all holes are clear and free of goo.

Mike

What hondadude said. He ALWAYS has a good tip.

Plus... there are two holes at the front of the carb where item #13 mounts. They look similar to the holes for the long bolts that hold #13 on. Make sure you spray pressurized carb cleaner through those holes. Those are the main jet air feeds.

Also, on top of the carb body are two little "tunnels" (for lack of a better description) one runs at a right angle to the carb throat and one is sort of on a diagonal. Those are the bowl vents. Make sure that carb cleaner sprayed into those comes out of the corresponding little holes that are inside the carb. You may be able to use your wire trick to sort of "explore" those passages and others. If you did not take #4 screw out and flush in that passage, do so as well.

It should have little more get up and go if you do all of the above.

If it doesn't...then it would be time for a check on the valve lash adjustment and maybe a compression check. A dry and then wet compression test, after the valves are properly set would tell a story.

Good luck.

thanks for all the tips, i will go threw all the spots on the carb more carefully. ill let u guys no. thanks again

hey hondadude i am going threw the carb again, i noticed i dont see a number 7 like u pointed out (the slow speed jet) the port is ther for it but has a plug ball type thing in it, i looked at the diagram for the one u posted and i do see the number 7 screw, however that looks to be for a bf100la ? i brought up a bf100sa and i dont see that number 7 on that diagram. so im guess my motor is a (SA) ??? any ideas on that? i just noticed that and hought id bring it up, i havent yet worked on the carb yet (it's been soaking for around 4 days so far) gona get to it tomorrow thow. thanks for the tips

hondadude: my correction i looked at ur link again, looks like thats for a bf100a carb? mines just a regular bf100 carb, mine has no number 7 and the other does, i dont no what the a stands for and not sure if mines a sa or la like i was sayn, would u have any idea by serial number?

The serial number would help identify it for sure. Yours must be an earlier vintage than I pictured. If it is, it probably has just a small straight slot screw where the slow speed jet is in the picture.

Remove that screw (carefully) and shoot carb cleaner or brake clean through that passage. Also blow it out with compressed air. That is a good access point to the slow speed circuit.

You should not have to remove the carburetor to do this.

Mike

update: i tore carb down nce again, every piece, let all parts (besides plastic) soak in sea foam for two day then i took carb out and ran speaker wire threw every possible port, all vent tubes, everything, used compressed air and break clean, everything seemed fine, then i let soak for another two days just to make sure, ran wire threw all ports again along with break clean and compressed air.
put everything back together on carb, went and bought bran new gas , and put bran new plugs in it, starts up if u choke it. the idle screw on top of car is maxed out ( fast idle) and it starts up and u can take choke off and it sits and runs very smoothly and consistant at a fast idle, i let it run for idk 2 mins or so, az soon as out back of the idle screw even a half turn it just dies! i mean its no even close to where it should idle and it dies. what could possibly be wrong i am wondering, feels like it has nice compression when pull startn it! i do not think its lacking on that part, i do however have a bran new compression tester if thats the next step i do not no. valve lash maybe? this is a cdi typ engine i do believe. any help thanks!
note: i also tried by passing the fuel pump and tried gravity feeding it into the carb directly

wishiniwasfishin.....me too!

Sorry to hear you're still having problems.

I would NEVER argue with checking and making sure the valves are properly adjusted and would encourage you to do so.

BUT! I think you still have a carb problem based on what you last wrote. It sounds as if the engine is running ok on the HIGH SPEED CIRCUIT of the carburetor but is falling down on the TRANSITION and IDLE circuits. The common denominator here, FOR THIS CARBURETOR, is the SLOW SPEED JET.

It is my opinion that there is still some blockage in that area and that is why the engine will only run well with the throttle plate opened up fairly wide.

While not a bad practice, I don't believe that soaking in Sea Foam is enough to get a carb properly cleaned. It is just not an aggressive enough solvent. I think that you need to get in there with CABURETOR SPRAY CLEANER and hose that SLOW JET and the "bleed" passage for it and the idle/transition circuits.

I read the back and forth you had with Mike about access to the slow jet and if yours is not the removable style, I recommend going at it from inside the carb body. Both with the access plug removed and then installed so as to redirect the carb cleaner spray through the passages so that you can SEE CLEANER EXITING THE IDLE PORT and, with the throttle plate held open from BOTH OF THE TRANSITION PORTS. This should also be done with the idle mix screw removed and the cavity covered with your finger for a portion of the cleaning. Then, use the idle mix screw cavity as a "spray point" to get the cleaner to move through the passages in a different way.

Other "spray points" are the passages that you can see that are at both ends of the carb that run parallel to the carburetor throat. They don't look like anything but a couple of extra bolt holes but they are very important to the flow of fuel. They should be hosed out generously with CARB SPRAY.

Just for reference, in some cases, I have used as many as 4 LARGE cans of CARB SPRAY along with an entire can of WD-40 to clean SINGLE problem carbs. Those little straws give the solvent the velocity it needs to wash away deposits and flush the passages clear of debris.

The only carb SOAK I have ever used that actually worked was BERRYMAN'S carb cleaner that comes in the bucket with the other drain bucket inside. However, I consider that cleaner to be too CAUSTIC/STRONG to use on these little carburetors.

I know this can be confusing and hard to digest when you've been fighting it for as long as you have. But, I'm giving you my best guesses here.

One other thing I would hope that you might consider is buying the Honda Carburetion Manual. It was just discussed in today's forum update in a post by hairdresser100. If you had that manual, then all of this would make much more sense.

Good luck.

cleaned carb one more time, still running the same, ran carb clean threw each sopt on the carb like crazy, burned up 3 cans, used compressed air, also checked float height to see if it was within spec. about ready to buy a bran new carb but beore i do so should i check compression? valves? could it be electric problem? maybe a vacume issue? timing? wouldnt thin it would be timing cuz its not back firing or anything like that whats so ever, thanks for any help

You don't say whether or not you are seeing a RELIABLE flow of carb spray form the idle and transition ports. If you are, then I would agree that the problem may not be "cleaning" related. However, if the ports are not delivering fuel the problem is still with the carburetor. Hard for me to tell sitting at this keyboard.

Is it an electrical problem?
While anything is possible, the fact that the engine runs ok on the main circuit and at higher rpm would suggest that it is not spark related. A stronger spark is needed for higher rpm than for an engine at idle so that suggests that the ignition is working well. However, I once heard a very wise man say that anyone that said they knew all there was to know about a magneto was crazy. Magneto ignitions have fooled many a better mechanic than me before.

Check and adjust your valves then check compression. It is the next logical place to go here. Tight valves and/or low compression could cause these symptoms.

Could it be a vacuum issue?...
You bet it could! A small intake leak could cause these symptoms. With it running as best as you can get it to without having to hold the throttle open, spray some carb clean around the intake manifold... especially at the carb to manifold flange. If the engine picks up rpm when you spray in a given area, then you probably have a leak at that spot.

There was another poster here just a few days ago that did buy a new carb for his older 100 and he said that, even though the carb was a bit different than his original, it worked great. So, if all else fails.....But, I would reserve that move for dead last.

Good luck.

got it! problem was still in the carb. I took carb back off yesterday, tore it all down and let it soak in a can with carb cleaner and it musta loosened somethin finally up, before i did that i sprayed carb cleaner threw the ports and noticed one of them not having much going threw it that why a figured let it soaked, pulled it out blew compreesed air threw then carb cleaner again, noticed alot more spray then coming threw the port, also put a drop of wd-40 on the needel and seat lol it seamed a little sticky i think it was from dryn it out so much from all the cleaners ha, but the motor runs like new! thanks so much to you guys that have helped me threw the steps!

Whew! That's a relief! I was getting worried that you were going to have to keep suffering! Good news is always a bit uplifting so, now, I can go out and slay one of my dragons (1991 Chevy 3.1 L with no spark) with a smile on my face.

For anyone else reading your ordeal, I will say that this case does go far to emphasize how difficult these little carburetors are to get cleaned after they have been 'let go" for a time. If you scroll to the top of this thread, you see that the correct solution was provided by the "first responder", racerone, followed by Mike and I pretty much agreeing with him. But most guys just don't realize that it takes some pretty involved gyrations to get all the crap out of what looks like such a small, simple, innocuous little device. Convincing them they "AIN'T DONE YET" can be almost impossible.

Now that you've been through the process, I predict that the time will come when, one day, you will try to help someone with one of these that loses faith and doubts what you're telling them.

The trick was, that you never gave up. So, I take my hat off to you for persevering and GITTINERDONE!!

STOP WISHIN AND GO FISHIN!:{)

FURSHUR TIME TO GO FISHING! thanks so much for all of the tips and workn with me threw it! you guys are awsome

This is an old thread, but I wanted to add to it for the record.

The instructions worked for me too! I have a BF100 LA that started showing the same issue ( would not idle) suddenly after working fine for 2-3 years. I have 0 experience in mechanics, but with the information in this thread I was confident enough to give it a try and clean the carb.

I had to clean the carb twice (using carb & choke cleaner, a can of compressed air and a thin wire). The second time, I noticed 2 VERY SMALL holes I had missed the first time. They are drilled in the internal side of the "tunnel" where the throttle "door" is located (sorry, don't know the actual names...). You actually have to rotate the throttle to see them, and they are minuscule (almost look like specs of dirt). Air intake?

Anyway, after cleaning those, the engine now purrs like a cat. So thank you to the above posters, and you were right, if it doesn't work the first time, take the carb apart and clean it again!

Stefd,
Welcome aboard the forum and thanks for the "added value" you provided to this thread via your experience.

The holes you describe are the fuel delivery orifices but the term "tiny hole" works too. As well as "door" for throttle plate and "tunnel" to describe the bore. They are descriptions that work and most can understand so that's all that really counts.

And, we all can certainly appreciate and fully relate to your description of the results you got for being persistent and following through...ie: purrs like a cat. THAT'S what sounds best!

Your post will undoubtedly encourage someone else to hang in there and that's GREAT!

Thank you so much for this thread. I had the exact same problem that several others have described, BF100 wont idle and hard to start. I had to pull the carb out twice but eventually something unclogged and now the motor runs beautifully. Quite a bargain too, 400$ (Canuckistan dollars at that) for a 1985 BF100 CDI and a Japanese built Achilles inflatable boat (no leaks!). Now that the motor runs well I cant wait toi take it out on the St-Laurence river!
Thanks again.