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Nikki carb question

#1

O

oldsman143

Hello,
I own a Craftsman MTS5500 lawn tractor with a Briggs Intek VTwin 24 HP. I removed the carb bowl for float inspection after my crankcase was floaded with gas. I somehow lost one of the jets. The left and right are apparently different as they have different part numbers. Does anyone know the difference or should I just buy both?


#2

I

ILENGINE

The difference is the size of the hole in the jet. Has something to do with the flow rate between the two cylinders. One cylinder has to have more fuel for the engine to run balanced.


#3

C

chance123

I "HATE" those Nikki carbs! The main jet is only held in by a small "O" ring. Gravity+vibration many times causes them to fall out. Your problem, however has little or nothing to do with the main jet. It is more than likely a bad/dirty float needle and seat that would allow fuel to enter the crankcase. A leaking float would do this too.


#4

O

oldsman143

Yeah, I figured I would just check the needle/seat and clean it. Apparently I lost one of the jets. I guess I need to buy both as I don't know which one I have. Of course, no one local to me stocks them so I must order online and wait. :frown:


#5

O

oldsman143

Got new jets, bowl gasket, and o-ring for fuel transer tube. Cleaned all and re-assembled. Engine starts and runs a short while only when choked. Will not run if choke is off. Any suggestions? :frown:


#6

EngineMan

EngineMan

You need more fuel to air, check the gasket between carb and engine.


#7

O

oldsman143

Should that gasket be an issue on an engine with only 135 hours on it?


#8

EngineMan

EngineMan

Did you take it off..? did you damage it in doing so..? and did you put it back on right..? It maybe one answer to your question, its a start..!


#9

O

oldsman143

Are you referring to the two intake gaskets? If so, I did remove the intake from the heads. It uses a rubber gasket with the plastic intake. As far as I know the were not damaged in the removal/replacement process.

When it starts, it will run about 5 or 6 seconds then die. Could it be the fuel pump? I did check it first when my original problem of not starting began. It wasn't a steady stream, more of a pulse. Is this normal?


#10

EngineMan

EngineMan

You better up the B&S engine numbers so that someone here may look it up for you.

The fuel pump will pulse that is normal, and is mounted on the No. 1 cylinder shield and allows remote fuel tank installations. The fuel pump will prime at 12” (30.5 cm) maximum lift. and the fuel pump pressure should be around 1.5 psi (0.1 Bar ). The pump is operated by pulsating crankcase vacuum from the engine. The vacuum pulse line is installed on the No. 1 cylinder valve cover.
Replace fuel lines and vacuum pulse line if stiff and brittle, and note: An air leak at the fuel pump pulse line hose connections will result in improper fuel flow.


#11

O

oldsman143

BRIGGS AND STRATTON
INTEK VTWIN 24HP

MODEL 445677
TYPE 0759B1


#12

EngineMan

EngineMan

That engine may have a fuel solenoid, if so is that working OK.


#13

O

oldsman143

EngineMan said:
That engine may have a fuel solenoid, if so is that working OK.
Click to expand...

Are you referring to the anti-afterfire switch on the bottom of the fuel bowl?


#14

EngineMan

EngineMan

Yes that is right.


#15

O

oldsman143

EngineMan said:
Yes that is right.
Click to expand...

What is the best way to test it? I guess if it is closed, no fuel gets to the cylinders.


#16

EngineMan

EngineMan

ANTI-AFTERFIRE SOLENOIDS
Begin troubleshooting the solenoid by checking for battery voltage at the spade connector (with the key switch in the start as well as the run position). The next check is to listen at the bowl of the carburetor for a distinct click when the ignition switch is turned to the on position. If a distinct click is not heard, remove the solenoid for further testing. To test the solenoid itself, attach one pole of a 9 volt transistor radio battery to the spade terminal and the other pole to the solenoid case or black ground wire if so equipped. A sharp distinct movement of the plunger should be seen.

A fuel shutoff valve must be all the way open to allow full fuel delivery. Anything less may be
responsible for a restriction in fuel delivery.


#17

O

oldsman143

EngineMan said:
ANTI-AFTERFIRE SOLENOIDS
Begin troubleshooting the solenoid by checking for battery voltage at the spade connector (with the key switch in the 都tart as well as the 途un position). The next check is to listen at the bowl of the carburetor for a distinct click when the ignition switch is turned to the on position. If a distinct click is not heard, remove the solenoid for further testing. To test the solenoid itself, attach one pole of a 9 volt transistor radio battery to the spade terminal and the other pole to the solenoid case or black ground wire if so equipped. A sharp distinct movement of the plunger should be seen.

A fuel shutoff valve must be all the way open to allow full fuel delivery. Anything less may be
responsible for a restriction in fuel delivery.
Click to expand...

Thank you for all the info. I will check this out.


#18

M

Mrsavaloy

Could it be the float height?
Is that adjustable?


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