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1974 B-100s issues...

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powderedtoastman

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It runs, but when it's idling it will slowly rev up, stay up, then rev down, stay down, then back and forth. When I switch it into drive, it will engage, but will not rev up at all. It will propel me forward, and I can twist the throttle all I want and it will just bog down and not open up. Any ideas what is wrong?
 
Is this a new issue? When did it run last without this problem? I am assuming this is a carb'd 4 stroke. If it has been sitting at all, I would pull and clean the carb. It sounds like there may be some gunk in there, or an air leak. Have you tried to drain the float bowl?
 
Ep4 said:
Is this a new issue? When did it run last without this problem? I am assuming this is a carb'd 4 stroke. If it has been sitting at all, I would pull and clean the carb. It sounds like there may be some gunk in there, or an air leak. Have you tried to drain the float bowl?
Click to expand...

Thanks for the response!!!

Basically, I just bought this thing from somebody I thought I could trust, and now I'm dialing a disconnected number. It is a carb'd four stroke two cylinder. Where can I look up how to clean the carb, or drain the float bowl?
 
http://www.boats.net/parts/search/Honda/Outboard Engine/0/BF100A LA/CARBURETOR AIR GUIDE/parts.html

There is a diagram here that should be what you are looking at. A service manual would help explain the process of carb removal. At the bottom of the carb is a bowl that the float sits in. This bowl has a drain nut on the side or bottom of it. If you remove it, fuel will run out. I am guessing the fuel will be dirty, or the bowl is sludged up inside or varnished. The only way to clean it well would be to remove the carb, then spray it down inside with carb cleaner, poke out all the holes in the throat and high speed jet, if it is accessible, then blow out with compressed air carefully. You will need to check the needle and seat when you have it apart, and make sure the float does not have any liquid in it. # 5 in the diagram is the drain, and #16 would be the bolts holding the carb on. If you are not familiar with the engine, I suggest taking a few pictures as you go, so you can put the linkage back on correctly. Be careful not to tear the gaskets where the carb mounts. When you remove the needle, turn it in until it gently seats and count the turns it took you to get there. Once cleaned, turn it all the way in, then back it out the # of turns you counted earlier. In most cases, many engines will be 1.5 to 2 turns out, on the low speed needle.
 
Well, I cleaned out every part of that carburetor, and it actually looked super clean inside. No residue, gunk, build up, nothing. I put it back together, fired it up, and it definitely idles much better now. Very smooth. However, when I shift it into gear it immediately dies. It seems like the idle is actually high when it's in neutral, but it still dies. Hmmmmm.....
 
Did you remove the needles? Most carbs have many small holes inside the throat that can get plugged up. Was there any varnish in the float bowl or on the needle & seat when you took the float out? I like to blow into the fuel inlet when I have the carb out, then turn the carb over to see if the float will close the needle. If it works like that, then you are pretty sure it will shut off with the fuel in it.
Have you checked the fuel pump? Any filters on the engine? Ethanol fuel can cause the lines to break down and come apart inside which clogs the filters and the pumps.
 
I blew into the fuel inlet, and the float is free moving and will close when I turn the carb upside down. The fuel pump seems to work great. I took it off and manually pumped it and it was gushing gas like crazy every time I hit the plunger on the back of it. I think I'll try and increase the idle speed and see what it does.
 
If your engine has points, make sure the idle mixture screw is somewhere around 1 3/4 turns out. I hope you blew cleaner through that passage. That is the passage that gets the fuel to the engine at idle.

Mike
 
Is the pilot screw the same as the idle mixture screw? I did some experimentation, and when I back out the pilot screw about 3-1/2 to 4 turns out it will run after I shift into gear.
 
That just suggests there is a lack of fuel getting in. This can be the fuel pump or still some restriction in the carb or fuel delivery system. The only other thing to make it lean would be an air leak on the carb or at the base. Close the choke about half way and then see it if stops stalling when you put it in gear. The mixture screw should not have to be more than 1.5-2 turns out.
 
You might try this. Drain the carburetor. Then blast some cleaner into the mixture screw hole and then blast some compressed air into the hole. Hopefully, it will clear the fuel and air passage in the idle circuit.

You did not say if you checked the compression. Sometimes, having to back out the mixture screw too far compensates for poor compression.

Most likely, you just didn't clean the carburetor thoroughly.

Mike
 
Understood. I will try to find my compression gauge, and I'll blow out that passage again. When I take the idle mixture adjustment screw out, I notice there is what looks to be a needle down there. How the heck do I get that out?
 
Does your carb look like this? If so, # 4 should be a solid needle that you can remove and clean the passage. Also, you need to make sure #8 and #19 are clean. There should be a hole all the way through #8 and then some other holes on the sides in most cases.
 

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If there is a part of a needle down there, you might be able to back probe it out with some small wire or pick. Look inside the barrel of the carburetor behind the butterfly for a pin hole in the top of the carburetor . That is where the fuel/air mixture comes out for idling. The idle mixture screw goes almost directly to that hole. You might just see that needle sticking out of the hole. Just a hunch. Be careful not to distort the hole from probing.

Mike
 
Also, did you take compression with the throttle at full throttle? You may have to remove throttle linkage then hold the throttle plate open by hand. It helps to have a friend do this while you pull the recoil starter or lash it open somehow.

It will generally make a difference in readings.

Mike
 
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