Honda BF40 Carb Leak

sailsman

Recruit
Joined
Jul 16, 2005
Messages
4
I just started my BF40 after the prevous owner let it sit for 9 months without starting. I know that many times the carbs need to be re-done when these engines sit for long periods of time, but I am not sure it is needed in this case. The engine starts, but does not idle well. I also noticed a fuel leak on the lower carb coming from a round metal (seal???) on the side of the carb. Not sure if the seal(?) can be replaced. Anyone have any tips on what could be the problem? Thanks!
 

Navigator

Chief Petty Officer
Joined
Feb 6, 2001
Messages
517
Re: Honda BF40 Carb Leak

Sailsman,<br />First off, welcome to the Iboats forum!!!<br />Remember, there are no dumb questions :) We're all here to help.<br /><br />First thing I would do is pull the plugs and replace if they look worn. Bad plugs will cause it to miss and idle rough. If you dont know when the last owner replaced them, just do it anyways. They're only about 8 bucks total for all 3.<br /><br />Pull the carbs and give them a once over. Its best if you invest in a manual if you intend to do the maintenance yourself. Iboats sells them here if you look at the top of the screen. <br />That said, to remove the carbs, remove the airbox silencer from the front of the carbs. It's that plastic black cover. Next remove the shift linkage from the carbs. Lastly, unbolt the intake manifold from the block. The intake manifold will come off with all 3 carbs attached. Now you can take each carb off separately and clean them thoroughly. The low speed ports are very small so you will need to make sure they are all clean. Compressed air and a piece of fishing monofiliment do a fine job of probing and cleaning them out. If the engine was laid up with the carb bowls full, you may find residue. Carefully remove the floats and make sure that the float needle valve isn't sticking. <br /><br />The fuel leak you mentioned, did you actually see it leaking or was it residue form a past life? Did the previous owner try to change out the high speed ports? If it is the metal plug leaking, that can be replaced. I'd just try to find out how it started leaking in the first place. Those parts usually do not leak and are sealed from the factory.<br /><br />Nav :cool:
 

sailsman

Recruit
Joined
Jul 16, 2005
Messages
4
Re: Honda BF40 Carb Leak

Nav,<br /><br />Thanks for the great advice. I replaced the fuel filter and plugs as well as the fuel/water filter after removing all the fuel from the fuel tank. The fuel was old and bad with out a doubt. The "old" fuel smell reeked! I will be cleaning the carbs as you described as soon as I get some parts. Is there a carb kit that I should buy or should I buy parts based on what I find after opening?<br /><br />Regarding the leak. When the engine was running, I could see the fuel leaking slowly from the lower carb round metal seal. I realy can't find out what the previous owner did to it since he can not be reached. Do you know how that round seal is removed and replaced? I would like to know before my manual arrives (already ordered) and what could cause it to break. The seal is located on the side of the carb, visable when removing the engine cover, above the bowl. Thanks again for your advice.
 

Navigator

Chief Petty Officer
Joined
Feb 6, 2001
Messages
517
Re: Honda BF40 Carb Leak

sailsman,<br />I dont believe Honda has a carb kit for the 40. Apparently there hasn't been that many requests so they never put one together. You can however, get all the part separately from Honda. Honestly, there are not really a whole lot of parts in the carbs themselves. Usually just a spray can of carb cleaner and a little common sense will get them squeeky clean. If nothings damaged, the only parts you may need are a set of new gaskets. <br /><br />Once you get them back together, you will need to sync the carbs to get it running perfectly. (it will start and run fine, but it wont be perfect) For this you will need a vacuum guage set designed for this purpose. You can throw a post in the Outboard non repair forum and ask where to get a decent set. Its a tool you will use many times so look at it as an investment in your engine.<br /><br />As for the Leaky plug, you've exceeded my experience in that area. I've never had my carbs that far down so I'd hate to lead you in the wrong direction :D <br /><br />Nav :cool:
 

argonaut

Cadet
Joined
May 14, 2005
Messages
18
Re: Honda BF40 Carb Leak

The carbs on my BF50 were clogged from old fuel and also appeared to weep fuel from the round seal on the side. I think that's a symptom of a clogged main jet. After rebuilding mine & getting out the green jellylike goo, the leak disappeared. Hope you have the same luck.
 

sailsman

Recruit
Joined
Jul 16, 2005
Messages
4
Re: Honda BF40 Carb Leak

Nav,<br />Got the carbs off and found that the lower carb had more scum build-up than the other two. In fact the top and middle carbs were very clean. One thing I noticed was that the float jet chamber seems more restricted than the others. When I blow through it with compressed air, (and my mouth) the other two carbs blow more through the same chamber. I have tried several solvents and compressed air through the jet side and line side. I have also tried to run some mono line with no luck. Anyone know any other tools techniques I can try to unclog this chamber of my lower carb? Thanks!
 

Navigator

Chief Petty Officer
Joined
Feb 6, 2001
Messages
517
Re: Honda BF40 Carb Leak

sailsman,<br />It sounds like you've got a nice piece of Goo stuck up there. Try submerging the entire carb in cleaner for 24 hours. (remove all non metal parts and gaskets first.) sometimes it takes a good soak to loosen up the gunk.<br /><br />All 3 carbs should be the same. I think you've found your problem.<br /><br />Nav :cool:
 
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