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Starting issues

J

Just357

New member
Hello everyone I have a 1995 Honda 4 stroke 40 horsepower outboard on my 19 ft Boston whaler center console.
It has sat with old gas in it for about 2 years I have replaced all the fuel fuel filter fuel pump three spark plugs and cleaned all three carburetors still having issues with it starting if I spray starting fluid or carb cleaner into it it will stop it won't stay running any help all three bowls if I loosen the set screw have fuel in them I'm not sure if it's getting the proper fuel it seems like it's starving is there anything else I can check maybe I miss something in the carburetor cleaning? Thanks for anyone that can give me some important I really appreciate it..
 
Hi,

Have you owned this a long time?

I assume you're usng clean, fresh fuel.

Have the valves ever been adjusted that you know of?

If it dies while spraying start fluid, it sounds like it might be getting TOO MUCH gas. Did you check float heights when doing the carbs?

Do you open the throttle some when spraying? It might not be taking in enough air thus my valve adjustment question. Or, you didn't get the idle circuits clean enough.

If you're using ether, try carb or brake kleen instead to minimize the risk of hurting your engine. Propane gas is the most reliable artificial fuel to use for testing to avoid engine damage but most people freak out when I suggest it. It's already a gas and naturally mixes with air for a near perfect "stoiciometric" ratio for powering piston engines. It's also less likely to start a fire. Think forklift engines

Or,, it could be having a spark problem or even dropping a cylinder.

Suggestions:
Check spark
Do a compression test

If those check out, you may need to re-visit the carb cleaning.

On these carbs the slow speed emulsion tube or "jet set" is EXTREMELY important and the tiny jet inside the tube is very hard to see and can be close to impossible to get properly clean sometimes. See item 19 in link below.


The little oring (item 2) on the jet set.MUST seal COMPLETELY or you'll have problems. If you didn't use new ones or were careless putting them on and damaged any of them installing the tube, you'll have problems.

Thr jet set tubes are known for cracking vertically, especially if the plug screw (item 11) that secures the emulsion tubes is over tightened.

Just tossing out some possibilities.

If you decide that you DO need to take another look at the carburetors, I have some cleaning suggestions for things that often get overlooked.

When you do get it to reliably start and stay running, you will need to vacuum balance the carbs for the best performance.

Good luck and let us know how it goes.
 
Hi Jgmo!

I’m currently cleaning my carbs and would love those cleaning suggestions. This is my second time cleaning. My jet set tubes seem fine but maybe I missed something elsewhere?

2 of my 3 carbs are working but the bottom carb isn’t firing unless I remove the air filter box and squeeze gas directly into the throat. I had to replace the float needle in this carb so I’m thinking maybe I didn’t set the float height properly? I’ve now adjusted it to be the same level as the working carbs but have a hard time believing that’s why my carb wasn’t firing in the first place.

Any advice would be greatly appreciated. Thanks!
 
Hi PY,

It is important to keep in mind that fuel gets PUSHED UP through the main jet and emulsion (mixing) tubes by atmospheric air pressure (14.7 psi) PUSHING DOWN on top of the fuel inside the float chamber/bowl.

The air moving through the carburetor horizontally from engine vacuum creates a "low pressure" to pull on the fuel but without that 14.7 psi pushing fuel from the bowl and helping, the fuel won't travel upwards.

That's why there are vents (usually 2...
...1 right & 1 left) for outside air to get inside the bowl.

Carb cleaning 101 is to make sure the vents are clear. They get plugged by specs of dirt or tiny bugs.

The vents are tiny passages so gasoline can't easily slosh out of the carb while turning or accelerating hard.

You can find the vents when the bowl is off by looking carefully at the inside top of the main body on each side of the fuel delivery stem.

Remember, the holes are very small.. A good flashlight helps.

Use the straw tip of the carb spray can to cover each hole and make sure liquid exits the outside top of the carb body.

This is EXTRA important for carbs that have been sitting a long time.

Once you see where the cleaner comes out, spray in there and make sure fluid comes out from the vent holes you first sprayed. A sort of backflushing to make certain they are clean.

NEXT....
...AIR JETS.

Your early "BG" model carbs will have 2 air jets inside the carb body. 1 low speed air jet and 1 main air jet. They are both fed outside air from passages that are parallel to the carb throat.
You'll see four holes on the front mount flange of the carb body. Obviously, the 2 big holes are the mounting bolt holes. The two smaller holes near the carb throat entrance are the air jet passages. Spray a generous amount of cleaner into both those holes, especially the slow air jet passage. It's the passage closest to the carb throat entrance. The main air jet passage is just above it and offset to the left.
If you remove idle mixture (pilot) screw, fluid should exit from that cavity as you shoot cleaner into the slow air jet passage.

It's important the mounting gasket holes align with the passages

I hope all this is understandable. If not, let me know.

I'm stopping here but there's still the delivery orifices in the carb throat to discuss and I'll continue when I get back.
 
Oh, there's more!

Look Inside the bottom end of that little jet-set tube and see if you can see light through the jet. If you have great vision you might. I have a 60X power comparator scope or otherwise I couldn't see it.

If that jet is plugged, the carb will never work correctly.

Also, prop open the throttle all the way and find all the tiny delivery orifices in the top of the carb throat on the engine end.

There should be about 7 or eight.

The idle orifice is the only one you can see if the throttle plate is closed.

The two just further in are the transition ports

The four or five further inside the throat are the high speed or mains.

See them?

Each one needs to be flushed with spray.

Use the spray can straw to cover each one and shoot it.

Watch for where liquid comes out for each one in the main body.

Good luck.
 
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