Honda BF2.3 carb clean

Phoenix of Hamble

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My Honda 2.3Hp outboard has been running somewhat roughly recently, and had started to need excess choke in order to keep it running.

A good check over was in order, so I brought it home to check it out....

It seems to be a common issue from previous threads on this forum, so I suspect i'm not alone in having this problem...

so.... last night I removed the carb, and discovered it to be really quite dirty, and after a good clean out it ran as sweet as it had ever done.... and thought it would be worthwhile sharing what is involved in detail for those less comfortable just getting stuck in, but willing to give it a go with a bit of guidance....

1] Remove the cover. This is done with the black rubber strap at the rear of the cover.

2] You will see three bolts that hold the starter cord (recoil system) to the top of the engine. It is worth undoing these three dome headed nuts, and removing the recoil unit, so that the whole cover can be put aside for better access to the engine

3] On the rear of the engine at the right hand side you will see a black plastic 'U' shaped item. This is the air intake. On top of this is a small clamp that holds the throttle cable in place. Loosen this clamp (don't undo completely), swing the small metal plate out of the way to free the cable and remove the cable from the clamp.

4] Now there are two bolts that hold the air filter on. they are on the right hand side, and towards the rear of the plastic air intake. The lower bolt is recessed a couple of inches, so you will need a socket wrench with an extension on it to reach the bolt. You will need a 10mm socket. Undo these two bolts taking care, and withdraw the two bolts one at a time. remove the air intake and place it in a clean location. They also hold the carb onto the engine, so make sure that the carb does not fall off. (it probably won't)

5] Carefully wiggle the carb by hand (don't use a lever or a hammer - its a delicate component!), and once lossened, lift it clear of the engine.

6] The choke cable and throttle cable will still be attached to the carb. maneouvre the carb so that these can be taken off (they have a small dog leg on the end of the rod/cable and just need orienting correctly to detach them)

7] Once the carb is clear, then take real care not to damage the paper gaskets that ensure and airtight fit to the engine and air intake. Unless you are unlucky, then these will be fine to reuse. If they get damaged, then spares are readily available, or you can make new ones from gasket material.

8] At the bottom of the carb is a metal 'bowl' with a 1.5" long pipe as part of the component. This 'bowl' is held in place by a single 10mm bolt. Undo this bolt (remember to take care of the gaskets!). Note the orientation for reassembly. Once removed, then you can start cleaning.

9] In the bottom of the carb is a metal tube (that the bowl was bolted to), this has a evry small hole in the side of it. This must be clear as this is how fuel enters the rest of the carb.

10] Next take a fine wire (soft as you can find) and gently (very) poke it through the hole exposed inside this 'tube'. This is the main jet, so must be clear, but is also very delicate, so take care.

11] Hold the choke and throttle fittings open (where the cables/rods connected) and two round 'flaps' will rotate to show you the main carb body as a cylinder. Blow through the cylinder to clear and dirt dislodged.

12] Finally reassemble, and reattach to the engine by reversing the steps above.

A couple of other tips.... when cleaning the carb, use a lint free cloth.... any threads or fluff left in the carb will cause havoc. Undertake the whole process in as clean an environment as you can manage... with any fuel system, cleanliness is critical.

Good luck!
 

Davy_S

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Good post! a lot of people seem to think you can simply tip in some carb cleaner and the jobs done. The bigger Hondas and Yamaha suffer from blocked carbs because people do not drain the old fuel off at the end of the season, these engines are lean burn with very small jets. Also rubber or neoprine o rings are used on the main jet holder, mixture screw and bowl drain, (bigger models) the use of solvent carb cleaners will, in time desolve the o rings. The only method is to completely strip the carbs and imerse the parts (jets) in carb cleaner. You have managed to take the trouble, and post how to do it. Well done!
 

YachtAllegro

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That's very interesting and helpful, thanks.

I hope I'm not hijacking the thread if I ask for a bit of related advice? Carburetors are new to me, having recently acquired a 2 stroke Johnson 3.5 outboard. However, last weekend the outboard was running poorly - it would start ok, but needed full choke to keep running and kept dying if I increased the revs. I wondered about dirty fuel / water in the fuel and after a bit of poking around undid a screw which I suspect was a carburetor drain screw. A bit of (probably) fuel came out, I put it back together, and after that it seemed fine.

I realised I'd had the outboard sitting on the pushpit with the tank vent open over a couple of rainy days. Could there have been water in the carburetor which needed draining out? Or am I barking up the wrong tree?

Cheers
Patrick
 

SAWDOC

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That's very interesting and helpful, thanks.

I realised I'd had the outboard sitting on the pushpit with the tank vent open over a couple of rainy days. Could there have been water in the carburetor which needed draining out? Or am I barking up the wrong tree?

Cheers
Patrick

I would have thought that leaving the tank vent open would more likely affect the performance of the fuel as the lighter components would evaporate particularly on warmer days, leaving a denser fuel remaining? Tank vent should not allow rain to enter tank.
 

VicS

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I would have thought that leaving the tank vent open would more likely affect the performance of the fuel as the lighter components would evaporate particularly on warmer days, leaving a denser fuel remaining? Tank vent should not allow rain to enter tank.

Id not trust any of my tank vents not to allow water to enter. I usually cover mine with a plastic bag and a rubber band if it rains or is a bit splashy.
 

ex-Gladys

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Just to add a point to this, much of the crud in the carb is just from "Varnish" left behind as more volatile fractions evaporate. I've had issues with motorcyles and my Tohatsu 3.5 over the last 5-10 years which perceived wisdom appears to put down to changes in petrol. The way to minimise having to strip your carb is to turn the fuel off and let the engine run dry as much as possible...
 

SAWDOC

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9]
In the bottom of the carb is a metal tube (that the bowl was bolted to), this has a evry small hole in the side of it. This must be clear as this is how fuel enters the rest of the carb.

10] Next take a fine wire (soft as you can find) and gently (very) poke it through the hole exposed inside this 'tube'. This is the main jet, so must be clear, but is also very delicate, so take care.

11] Hold the choke and throttle fittings open (where the cables/rods connected) and two round 'flaps' will rotate to show you the main carb body as a cylinder. Blow through the cylinder to clear and dirt dislodged.

12] Finally reassemble, and reattach to the engine by reversing the steps above.

A couple of other tips.... when cleaning the carb, use a lint free cloth.... any threads or fluff left in the carb will cause havoc. Undertake the whole process in as clean an environment as you can manage... with any fuel system, cleanliness is critical.

Good luck!

Re 9 above
I put a tiny allen key through the hole, gave it a little wiggle and out it came on through a similar hole on the opposite side of the tube.
Then I thought well have i just disturbed something or have I actually provided a clear flow route?? Other than blowing through the choke and throttle flaps as suggested, how else can the main jet be cleared?
Reassembled and no go - very dead sound suggesting that flow is not getting through to carb.

Second query,
On removal of the air filter one sees a short open ended rubber hose which appears to be a fuel overflow or return hose? Anyone clear on its purpose and should it be connected to anything at the open end?
 

blackfish

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Last edited:

KAL

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THANK YOU Phoenix of Hamble for the amazing update on carb cleaning.

I used your notes to clean my carb, and also took some photos, which I put into a doc for my own reference for next year.

If this helps please feel free to use:
https://docs.google.com/document/d/1J_LEq5sY4abs75jeYxCSj3hdqpkzcMXykbc7XkavrQw/edit?usp=sharing
Thank you, thank you, thank you, to both Phoenix and Sailingman111 for this. I was in the depths of despair last night, as we're going to need this Honda 2.3 very soon, but woke up early and tackled it, based on your excellent instructions and photos.
The bowl was quite corroded inside and was full of kak. Cleaned all jets with nylon bristle as suggested and lots of carb cleaner everywhere. Now running 'as sweet as ever'!

Magic. Bless you.
 

BlueChip

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One very useful piece of kit I have found for cleaning carbs and other boaty stuff is an ultrasonic bath.
I bought one on eBay some years ago for about £25 and its so handy for cleaning carbs and SWMBO's jewellery
I just drop the take the float chamber off my carb, unscrew all the jets and drop it in warm water with some fairy liquid for about 10 minutes.
It comes out spotless.
 

brentkend

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One additional tip. My Honda 2.3hp outboard would start fine with the choke, but after it warmed up and I closed the choke it would not idle. I cleaned the Main Jet and the Main Nozzle, reassembled and it still would not idle. However, then I carefully removed the Pilot Jet (a black plastic jet assembly accessed from the top of the carb) with a pair of needle nosed pliers, cleaned it with a nylon strand with some carb cleaner, and that resolved the idling issue completely.

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