B+S vert, twin 44R677-0021-G12, 24HP Idle issue.

[subby]

My Husky/Craftsman 917.203900 wants to stall at minimal idle speed with a rough idle.

I checked the plug firing with a spark tester, but it has good spark on both cylinders at speed and idle. Apparently the carb idle circuit has a problem, or the mixture adjustment maybe be off. I doubt if the carb needs a rebuild. Before I get into it, I am going to pop the hood and try the idle adjustment and check the fuel bowl for water etc. Nice engine in a questionable mower? The RS 800 CVT Variator requires constant cleaning to keep it functioning. This requires about 3-4 hours as the fuel tank has to be removed to access the CVT. I have installed a temporary fuel tank on the rear of the mower to eliminate constant removal of the fuel tank. Not handsome, but it functions! The original install according to sears manual was to be an under the fender tank, this one came with the under seat tank, a losing preposition!

Thanks,

Subby

 

[ericm979]

Since you moved the fuel tank, that's the first suspect. Check fuel flow and tank venting.

Poor idle is often due to poor mixture which in turn is due to gum in the jets from gas evaporating in the carb. The idle jet passages, being the smallest, are the most affected. Disassembling and cleaning the carb bowl and jets is usually a first step.

 

[radios1]

there's seafoam, which you could put into your tank, you could try blowing out the idle circuit with a blowgun and air compressor.. a fix for the RS 800 CVT is here. General Transmissions offers solution to Sticky Shift Syndrome on some transmissions | Outdoor Power Equipment btw, the tractor was made by Husqvarna for Sears..

 

[mini14]

Actually for me first step is spraying around the intake gaskets with carb cleaner to check for air leaks.

 

[Dave M7040]

Most B & S carbs incorporate an emulsion tube to break up the fuel and mix it with air.

In the B & S world it is called: Carburetor Nozzle 299740

The main jet is unscrewed to access the tube.

Use a flat screw driver that exactly fits the slot in the main jet or you will end up in a big mess.

The holes often need to be poked out with a fine strand of wire. You cannot get it clean without removal!

See photo.

Dave M7040

 

[tomplum]

No removable emulsion tubes on these. If your fuel supply is good, you can try to drain the crud out by removing the solenoid on the bottom side of the bowl. Beyond that, if you're not experienced with this carb- you may want to have it serviced or simply replace the carb (OEM). You can try removing the shroud, the top cover (3 screws) and finding the two holes that have the brass fuel pipes on them, give them a quick blast of carb spray to clean the mains. Then quickly put the carb cover on and start the engine and run it for minute only to see if there is improvement before you put the shroud on. If not done quickly the cleaner can distort the jets o-ring or the seal below the pick up tube.

 

[5030]

Sounds to me like a gummed up carb. Seafoam time.

 

[DieselMonk]

I’d be using Seafoam too.

 

[5030]

I tend to use Seafoam all the time, in every tank of 'crapolene'.......:laughing:

 

[subby]

Hi,
The majority of people don't realize how costly a simple lawn mower is in terms of replacement parts. The cost of a new B+S Carburetor for this twin is listed at $197.00 to$220.00. A new engine is $1500.00 list. All similar Koehler's and others are in this same price range 0r more. A 17.5 HP for a MTD is nearly the same. When I was into repair I was going to rebuild a blown Sears engine which I received, the part cost exceeded a complete new engine by $300.00. I had a recent model Ingersoll air compressor for repair, a guy let it run low on oil and kaput! The cost of a new one was about 800 to 1K. Part cost was $800.00, no labor. It is an unfortunate situation as 90% automated machine work on die cast parts! End cost is probably a third or less of the retail price. My son's Big Cadet 2000 had a simple oil leak on the crank, that engine if not repairable would have cost $1500.00. A local shop here is really rip off place for parts, so you have to hunt a reasonable part cost and do your own labor!