B&S Intek v-twin 23hp surging, only runs on choke, low rpm, etc....

Jimmyl · Apr 12, 2019

Background (lengthy)
22hp B&S on my 10yr Craftsman exploded end of last year (shattered rod, piston, bent and cracked cam, scarred crank, 2 broken engine housings where cam sits.) Sounded impressive!! 
Just purchased used 23/48 Husqvarna, 23hp Briggs v-twin, model YTH2348, engine 445577. They said mowing deck didn't work. Feared clutch, turned out to be seat switch! Awesome.
Ugly mower that clearly sat outside, but solid.
Pulled working carb off grenaded engine. This one rusted inside and I think O-rings swollen. Well, first time I mowed, engine sounded terrible when upping rpm's or a load. Turned out to be bent intake rod. Valve stuck. Rep both from parts from grenaded engine.
Of course, other cylinder valve stuck, bending other intake pushrod. Also Rep head and pushrod for that cylinder.
Valves all adjusted. Like 6 times double checking things.
I now have a mower that starts right up!! Only runs on choke. Surges, rpm's don't seem high enough. I can pull down governor rod and rpm's will climb like it has full power, but engine pulls governor rod back up, lowering rpm's. Again, it surges, gov rod moving up and down.
Governor adjusted correctly.
Fuel issue, or something more sinister? I'm all ears for any help. Grass is high.... 

bertsmobile1 · Apr 12, 2019

Jimmyl said:
Background (lengthy)
22hp B&S on my 10yr Craftsman exploded end of last year (shattered rod, piston, bent and cracked cam, scarred crank, 2 broken engine housings where cam sits.) Sounded impressive!! 
Just purchased used 23/48 Husqvarna, 23hp Briggs v-twin, model YTH2348, engine 445577. They said mowing deck didn't work. Feared clutch, turned out to be seat switch! Awesome.
Ugly mower that clearly sat outside, but solid.
Pulled working carb off grenaded engine. This one rusted inside and I think O-rings swollen. Well, first time I mowed, engine sounded terrible when upping rpm's or a load. Turned out to be bent intake rod. Valve stuck. Rep both from parts from grenaded engine.
Of course, other cylinder valve stuck, bending other intake pushrod. Also Rep head and pushrod for that cylinder.
Valves all adjusted. Like 6 times double checking things.
I now have a mower that starts right up!! Only runs on choke. Surges, rpm's don't seem high enough. I can pull down governor rod and rpm's will climb like it has full power, but engine pulls governor rod back up, lowering rpm's. Again, it surges, gov rod moving up and down.
Governor adjusted correctly.
Fuel issue, or something more sinister? I'm all ears for any help. Grass is high.... 

If you can manually move the governor rod and the engine runs well your problem is a lean fuel :air ratio that is not rich enough to sustain high speed running.
So either not enough fuel getting to the carb or too much air leaking in after the emulsion tube.

Last one first.
Get a trigger pack NO A SPRAY CAN of your favourite dewatering fluid , WD40 etc.
Hold the governor wide open and saturate all around the mainfold.
Clouds of white smoke = air leak

Second one is a bit harder.
Get some sort of fuel tank, pinch one from the other mower or a push mower, motorcycle etc etc.
Connect it to the carb directly, hold it at shoulder height and start the engine with your 3rd hand.
runs fine confirms carb is good but fuel supply is bad and visa versa.
If the mower has been stored outside suspect debris & water blocking the outlet in the tank.

cruzenmike · Apr 13, 2019

You have to be VERY careful trying to move the governor arm when the engine is running. I made this mistake once and it did not end well. In the absence of a governor, the engine will run at the maximum allowable speed (to the point of blowing up) based on the presence of air, fuel and ignition. When a governor is properly adjusted, the default position is to have the engine run at wide open throttle and it is the position of the throttle on the mower, via the cable, that holds the engine revs back. Also the tangs on the carb/governor assembly are what determine the top no load RPM when the throttle lever is set to full throttle. So when you say that the governor is properly adjusted, it may not be. I have spent endless hours adjusting the governors on my engines and I still have to run it through a few times before putting everything back together.

Another issue may just be the carb jets. I had to replace the o-rings on both jets in my 24 hp Briggs. Ethanol does a real number on the rubber inside the carbs. If fuel can leak past the jets it will cause surging that cannot be fixed without replacing the o-rings.

Jimmyl · Apr 14, 2019

Thank you all so much for your responses! Think I'm fixing to get out there and give those a try. (honey-do's are finished!)

Jimmyl · Apr 15, 2019

Haven't been able to get to it yet, but did order a seal kit for the carb....

Jimmyl · Apr 19, 2019

Cleaned and rebuilt the carb last night. I'm hopeful this was my problem!
Completely clogged thru those two holes thru the carb body. Pulled out a metal brush bristle and with that and WD40 as a cleaner I got them open. Also cleaned thru the jets. Replaced all O-rings and rubber gaskets.
Guess I'll find out tomorrow.....

Jimmyl · Apr 21, 2019

Purred like a kitten, so the carb rebuild did the trick!!

B&S Intek v-twin 23hp surging, only runs on choke, low rpm, etc....

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