Honda BF7.5 won’t idle, so far I’ve

[MaxGlide]

Honda BF7.5, serial number 1602841
Initial problem would on run a bit with choke and die out.
Took carb off, used carb cleaner and compressed air to clean mixture screw opening, screw to left of that. Removed bowl, cleaned main nozzle, including tiny holes. Cleaned mini filter in fuel pump, main filter seems good. Made sure no leaks in fuel lines.
Now motor runs better when I rev the throttle, but dies out when rpms drop down (before only ran with choke full on)
Could it be fuel pump?
Should the inline fuel filter level drop as shown in picture? I pump it full before starting it.

 

[km1125]

Did you soak the carb? There are passages inside for the low speed circuits and if they're plugged it won't idle either.

The inline filter... if you orient it vertically then it should fill all the way. If it's horizontal it won't be able to get the air out of the top half, so it will always seem half full.

If you suspect the pump, then just use the priming bulb. Pump it a couple times while the engine is running. The fuel pump could be completely bad and you would still be able to keep the engine running on the priming bulb all by itself.

Is the float set correctly? Does the bowl stay full of fuel?

How have you adjusted the mixture and the idle speed screws?

 

[MaxGlide]

Did you soak the carb? There are passages inside for the low speed circuits and if they're plugged it won't idle either.

The inline filter... if you orient it vertically then it should fill all the way. If it's horizontal it won't be able to get the air out of the top half, so it will always seem half full.

If you suspect the pump, then just use the priming bulb. Pump it a couple times while the engine is running. The fuel pump could be completely bad and you would still be able to keep the engine running on the priming bulb all by itself.

Is the float set correctly? Does the bowl stay full of fuel?

How have you adjusted the mixture and the idle speed screws?

I didn’t soak it. What should I soak it in?
Don’t know if float is set correctly but did not mess with that. Just did main nozzle, mixture jet, sprayed every channel I could find.
Don’t know if boat stays full, how would I check that?
I have mixture screw set at recommended setting (1 - 7/8) and tried adjusting more towards 2 turns as suggested. Idle screw set properly

 

[MaxGlide]

Should this main nozzle have two little o rings?

 

[km1125]

If your float bowl has a drain, then after the engine quits you drain what's remaining in the bowl. Do it once when the engine is running right so you know how much to expect, then when it quits you drain it and compare to that amount.

When you flip the carb upside-down, typically the float should be level. If it's not, you can bend the tang that hits the float valve to adjust. Check out some youtubes for pics or examples. Actual specs will give you a measurement, but if you get it level it works 99% of the time.

Normally you'd soak the carb body in "carb dip" solution for at least four hours. Sometimes it takes multiple soaks to get it done. There are a couple small passages inside that feed the low speed circuits and they can get plugged up.

The main nozzle typically does NOT have o-rings. just should fit fairly snugly. Some are pretty loose and will drop out though when the main jet is removed.

If you have some air pressure available, then you can spray the carb -with the throttle closed- from the "engine side" backwards towards the input of the carb. That would force air through the small idle circuits. If you alternate spraying carb cleaner and then using the pressure you might be able to dislodge whatever is plugging the idle circuit(s). It's the tiny hole(s) between the throttle plate and the engine that supply idle mixture.

 

[MattFL]

A hot ultrasonic cleaner can do wonders for those tiny fuel passages.

 

[MaxGlide]

If your float bowl has a drain, then after the engine quits you drain what's remaining in the bowl. Do it once when the engine is running right so you know how much to expect, then when it quits you drain it and compare to that amount.

When you flip the carb upside-down, typically the float should be level. If it's not, you can bend the tang that hits the float valve to adjust. Check out some youtubes for pics or examples. Actual specs will give you a measurement, but if you get it level it works 99% of the time.

Normally you'd soak the carb body in "carb dip" solution for at least four hours. Sometimes it takes multiple soaks to get it done. There are a couple small passages inside that feed the low speed circuits and they can get plugged up.

The main nozzle typically does NOT have o-rings. just should fit fairly snugly. Some are pretty loose and will drop out though when the main jet is removed.

If you have some air pressure available, then you can spray the carb -with the throttle closed- from the "engine side" backwards towards the input of the carb. That would force air through the small idle circuits. If you alternate spraying carb cleaner and then using the pressure you might be able to dislodge whatever is plugging the idle circuit(s). It's the tiny hole(s) between the throttle plate and the engine that supply idle mixture.

I think I may have figured it out. Like a dummy, I totally forgot to clean the main jet that you unscrew to get the main nozzle out. Gonna do that now and report back!

 

[Alumarine]

These carbs are really, really fussy about cleaning.
Not that this is causing your current problem but are you sure the filter is installed in the correct orientation?

 

[MaxGlide]

So I figured it out. It was DEFINITELY the main jet. Took carb off again and main jet was plugged. Clean out and back on, started immediately, ran beautiful... for 2 minutes, stalled again. Removed carb AGAIN and during removal noticed that fuel line was brittle and tore easy. Install all new hoses and inline filter and BOOM! Started right up and runs like a top.

 

[MaxGlide]

Additional note, bought a generic fuel filter. The brass mesh was too coarse and still letting particles thru. Now have proper Honda filter on line going in to fuel pump AND between fuel pump and carb.