MS230C carburetor Puzzlement

[dougand3]

The first time I saw that MS250 IPL, I asked WTH???? Stihl has figured out a way to replace a line between the carb and pickup with 6 lines, T's and maybe disgronifacators.

These carbs are ~ $10-12 AM online.

 

[Hammermechanicman]

On this particular carb it's not possible to hook them up backwards. The supply line can't stretch to the purge line and vice versa. The diagram above isn't the same carb setup. I'll see if I can find the one I have.

Does the carb have 1 or 2 nipples to attach a hose to? The 230/250 usually has one but people sometimes ditch the goofy plumbing and install a carb that can use a purge bulb.

 

[StarTech]

The ms250 has a complicated primer system. It is not an air purge, it pushes fuel into the carb. The carb only has one fitting.View attachment 53611

Have you read the service manual?

Push home the fuel pump (short
intake stub facing the air filter)
until retaining tabs snap into
position.
– Connect suction hose from
carburetor to the short stub on
right.
– Connect hose from connector to
long stub on left.
The hoses must not be
interchanged.

So the primer does suck fuel through the carburetor.

Now one possible is a stuck main nozzle check valve (in open position). Unless it can close all the primer would do is suck air in through the main nozzle as it would the path of least resistance.

 

[Fish]

Can you flip the primer bulb over, it may be backwards.

 

[beaverplt]

Have you read the service manual?



So the primer does suck fuel through the carburetor.

Now one possible is a stuck main nozzle check valve (in open position). Unless it can close all the primer would do is suck air in through the main nozzle as it would the path of least resistance.

The Primer does suck fuel up TO the carb, but not through it. I just went over the primer hoses for the third time to be absolutely sure there's no air leak. I have the carb off and when I push the primer bulb, I get a strong flow of fuel coming up from the tank. I gotta believe at this point that something inside the carb is blocked so badly that the sonic cleaner isn't getting to it.

 

[Hammermechanicman]

For fuel to flow through the carb the diaphragm needs to be depressed so the metering needle opens. Is the impulse line connected to the barb on the cylinder to the handle assy? If you remove the carb and put a drop of oil in the small hole of the intake boot and pull the rope you should see the oil suck in and then blow out with crankcase pressure. If that is good you can pressureize (max 7 psi) the fuel inlet barb on the carb with the carb bolted in place and holding throttle wide open and pull the rope vigorously. With each revolution of the crank you should see a slight drop in pressure when the metering needle opens. Also, pinch off the line to the tank vent and see if that makes a difference.

 

[Hammermechanicman]

Just so you know. The primer bulb does not fill with fuel. It pumps air into the line for the tank vent to pressurize the fuel tank to push fuel into the carb. If you pull the line off the carb and pump the bulb it should spray fuel out the line to the carb. Stupid attemp at an easy start design.

 

[Fish]

Reassemble in the reverse
sequence.
VA 135RA221
– Push home the fuel pump (short
intake stub facing the air filter)
until retaining tabs snap into
position.
– Connect suction hose from
carburetor to the short stub on
right.
– Connect hose from connector to
long stub on left.
The hoses must not be
interchanged.

 

[Fish]

I haven't watched this yet.

 

[Hammermechanicman]

To the OP. This is a 251C. Does the carb you have look similar to this with 2 barbs on the carb or does it have a single barb?