What is the cause of only getting 75% power at full throttle , but 100% with a bit of choke .

[909]

1995 Johnson 9.9 has been sitting for years

Starts perfect, idles perfect. Linkage / Butterfly opens 100%

Only gets 75% power at full throttle. Needs a bit of choke to get 100%

What's the cause

 

[Faztbullet]

Fuel pressure, float level or high speed jet restriction

 

[racerone]

If motor sat for years with fuel in the carburetor it will need cleaning.-----Test for spark on both leads too.-----Do a compression test.----If good then clean the carburetor.

 

[909]

Fuel pressure, float level or high speed jet restriction

Thanks

If motor sat for years with fuel in the carburetor it will need cleaning.-----Test for spark on both leads too.-----Do a compression test.----If good then clean the carburetor.

Thanks . Spark is good. 120 psi dead even on both cylinders

 

[flashback]

It's running lean and choking it improves the mixture. Carb needs cleaning most likely.

 

[Roadking57]

since its running fairly ok you can try pouring a capfull or two depending on how much fuel is in tank, of sea foam or your fav brand of varnish remover. run it thru and see if it improves. Cleaning the carb is the best way tho.

 

[clemsonfor]

since its running fairly ok you can try pouring a capfull or two depending on how much fuel is in tank, of sea foam or your fav brand of varnish remover. run it thru and see if it improves. Cleaning the carb is the best way tho.

More like a whole can in a few gallons for any hope of that working. A capful in a fuel tank is nothing. Pouring into the carb throat does nothing to clean out the restricted orifice since it goes directly through the throat into the crank case.


But to answer the guys question if I was to just have one guess as to his problem and a fix I would say remove and clean the carburetor. I would say there is something restricting the High speed jet.

 

[jimmbo]

An off idle stumble is often caused by a Lean Idle Circuit. There might be a bunch of Gum/Varnish in the Area, which requires removal of the carb, and removing the Welsh Plugs and cleaning all the stuff out. I have used Power Tune, or Combustion Chamber Cleaner added to the gas, as it is more effective than SeaFoam, which I think is quite Useless. Sometimes the Chemical Cleaning works, but not all the time, as it can dislodge the Gum which then proceeds to really block the fuel.
Same goes for the High Speed Circuit, if there is a lot of Crap in the Fuel Bowl, the Chemical Treatment, may end up plugging the Main Jet.

The only proper way to clean a carb is to remove it, clean it, replace worn parts, Adjusting the Float, reassemble, install, check/adjust the Carb-Ignition Sync.

 

[909]

Would purchasing an ultrasonic cleaner solve the issue.

Have my eye on a brand new 2 liter unit with heater for under $80

How do you adjust the float.

 

[Roadking57]

I have a hornady heated ultrasonic cleaner and I like it. I use it to clean small carburetors a lot. Cleans my queens jewelry as well.

Most floats are adjusted by carefully bending the tab the needle hangs from just a tiny bit at a time. You have to picture in your mind as the float is pushed up by fuel as to which way you need to bend the tab. Looking at it upside down when you install it can get you confused. I hold the carb in my hand upright and blow air thru the jet and slowly push the float up until the air I'm blowing with my lungs cuts off (very low pressure). Then you can see where its shutting off fuel. If the float goes too high then you bend the little tab up a tad bit and do the air test again. Very small adjustments. Some manuals have an actual measurement of where the float should be set. Usually accompanied by a drawing showing where to measure from, like the edge of the carb body to the bottom edge of the float.

 

[909]

The seller says the 2 liter ultrasonic dish is :

5" x 5" x 3.25"

It narrows at the bottom to 4" X 4" x 3.25"

Would this fit a carb , or would I have to flip it and clean twice .

 

[Roadking57]

I have no idea. Measure your carburetor and see

Make sure you remove any and all plastic and or rubber parts that could disintegrate and go easy on the solvent you use

 

[Faztbullet]

Got a Habor Freight ultrasonic several years ago and some #202 solution and it works good

 

[909]

I picked up the 2 L ultrasonic cleaner.

4 x 4 x 3.25 will cover the entire carb

 

[909]

I adjusted the float, cleaned the carb, and it works well.

The nipple was worn, float was high causing flooding.

The solution was the lower the float, forcing the nipple to seat properly in order to seal .

The nipple is worn will have to be eventually replaced. But for now, it works well. I also will never spray carb cleaner inside an assembled carb ever again . There is rubber , and gaskets everywhere , which is what I suspect caused the deterioration in the first place. Take it apart , or bring it to someone who will do it properly.