Logo
FULL SITE MENU

Getting my 20 running again!!

Mystery solved. It looked like a fixed bushing but after a sonic bath some dismantling lubricant and managing to get pressure from a wrench (one jaw on the end of the slow tube and one jaw on the outside end of the main tube that houses both jets) it squeezed out as a pair. The slow jet needs replacing but I am back in business. Thanks very much for your help. For anyone reading, the slow jet only comes back out of the main emulsion tube after you remove them both from the carb body as a pair. It wont pass all the way through the main emulsion tube.
 
So, you're saying that the top of the main emulsion tube snapped off and was stuck in the hole??
If so, that's a new one for me.
 
No. Not saying that. Just that what l had previously described as a sleeve or bushing, was the inboard end of the main emulsion tube projecting up into the carb throat. It was stuck hard initially (hence my question whether it was fixed) but after a sonic clean and some dismantling oil it pressed out bringing the small tube with it as a pair. Once out they can be separated (as you already know…). After a further clean they now slot in and out easily.
 
Ok, that makes sense.
Glad you finally figured that out.

That main emulsion tube typically falls out on it's own when the plug holding it in is removed.

I think that, because you said that the screwdriver slot in the plug is deformed, it was way overtigtened and the main emulsion tube was jammed in there and also the jet set was cracked. As a result, I would consider replacing both tubes and the plug as there has obviously been distortion/damage done to all three.

You say the accelerator pump delivery tube and orifice are clear. I am interested in how you went about determining that and if you tested for the stream of fluid from the orifice. Did you use carb spray, with the straw, to "backflush" the orifice?

If this carb sat a long time with old gas in the float chamber, I would be pretty worried that the primary fuel jet could be plugged. Not to be confused with the main jet, the primary jet is unique to that carburetor and plugs easily because it is so small. Getting it clear can be difficult because it's up inside the brass tube that's in the main body on the opposite side from the SE dip tube location. It's next to the accelerator pump piston plunger rod and both can be seen when the float chamber is off.

If the primary jet is plugged, the engine will start and run but will never reach full power.
I have never found a specification for the size of that jet. I only know that when it will pass carb spray, the engine will reach full rpm.

The primary jet nor the tube are removable or replaceable.
 
I tested the accelerator pump jet by fitting a syringe on the end of the pickup and squirting a few mls of isopropyl alcohol through. Similar with the primary jet. I think it was blocked initially. I poked a v thin wire down it followed by a syringe of alcohol again. All looking good now. As I mentioned, I am hoping this all cures my mid range bogging.

I have another problem that I am crossing my fingers might also be helped/solved by all this. I will certainly welcome your comments.

The problem is that the motor is cutting out after 30 seconds of high throttle. It will run all day on idle and will also get the rib on the plane with two people on board at 2/3 throttle and will run happily like that without a problem.

But after 30 seconds of full throttle (planing with four on board for example or going extra fast two up) it suddenly drops to idle, chugs for a couple of seconds and stops. Will start again immediately and happily rev back to 2/3. Any ideas on this?

I have kind of assumed it is an overheating problem triggering an auto cut out. Although that is a bit odd when the outboard has only been running for a couple of mins.

Thermostat replaced - same problem. Full flush through, running the engine in a water butt with cleaning fluid - still same problem.

Wont be able test the rebuilt carb for a few months now but do you have any experience of a similar cut out problem?

V interested to hear your thoughts. Cheers.
 
HI,

Well, you might have a bit of blockage in that primary jet circuit.

That's my first guess.

I own TWO good quality ultrasonic cleaners but I wouldn't rely on them to get one of these carbs completely clean.

I would blast the tube with the straw of a carb spray can over the tip of the tube. I would then prop open the throttle all the way so that you can see the high speed deliveey orifices at the top of the rear of the carb throat.

With the throttle plate wide open, you can see all the delivery orifices (idle, transition, high speed). Cover each one individually with the carb spray straw and blast each one. I call that backflushing the circuits.

You should then locate the low speed (idle) air and high speed (main) air passage inlets and blast each one with carb spray.

Those inlets are on the front mounting gasket flange of the carb.

The two inlets are near each other on that flange above the carb throat. The main air (high speed) is the larger of the two and is mounted above and slightly offset to the left from the low speed (idle) air inlet as seen looking into the front of the carb body.

Fluid sprayed into the high speed air inlet will pour out of the main well passage that the emulsion tubes and main jet are mounted on if the retaining plug is removed.

If the idle mixture screw has been removed (it should be for proper cleaning) fluid sprayed into the low air lbeed inlet will exit from the mixture screw cavity.

You can backflush the air bleed circuits by spraying into the mixture screw cavity (low speed) and into the main well "tower" to ensure they are clear. The fluid should exit the flange inlets but will also exit the delivery orifices in the carb throat.
Any way you can block other areas (I use my thumb and fingers) that the fluid exits from will increase the pressure and flow and will make the cleaning more effective.

I don't like and don't recommend using needles, files, drills or wire to clean with unless great care is exercised to avoid accidentally enlarging or deforming jets and passages.

Not ensuring that a 6 to 8 ft. stream of carb cleaner will exit the engine end of the carb from the accelerator pump tube nozzle may result in performance loss.

I honestly can't explain why these Honda (Keihin) carbs that have accelerator pumps seem to rely so heavily on that circuit working like that but can only say that I know it just IS.

I also can't explain why the acceleratot pumps on these are so terribly flawed and short lived. Not even worth rebuilding, in my opinion, as the engine will run fine even with the pump piston removed!

It's another wierd thing I've seen in the carburetor "world".
 
Something I should have asked in the beginning:

Are you the original owner?
AND
Where do you normally use the outboard?
.Actually, at what elevation is the water you run in?
That can be important for a carbureted outboard.
 
Back
Top