b$s v 20 hp engine question

[corvairbob]

i just got this mower the other day, the guy claims it has a misfire on the left cylinder looking at the front of the engine. however, i can pull the plug wires off one at a time and the engine still runs so that tells me there is no misfire. but it stumbles kind of like it may have a dirty carb. when i start it i need to have the choke out about 1/3 so it will run smooth. then after a while, i can push it in but to be honest, i have not yet ran it for more than 10 minutes and it is 60 deg out so that may change as it warms up.

but when cold started it does do the normal surge as most do until they do warm-up. but to save time maybe someone can tell me if this is a normal thing? i'm thinking the guy that sold it to me did not realize that it may have a carb issue and just did not want to mess with it. he already put a 20 hp engine on it a few years ago it came with the 18.5 engine. so i do not mind digging into the carb but before i just wander into something that is as simple as an adjustment i figure someone here just may have the fix. the mower is in real good shape oil is clear new filter tires are good frame is clean so i'm thinking he did take care of it and service it when needed. and the new engine kind of tells me that also.

thanks

 

[corvairbob]

so i managed to find a few YT videos and discover the issue may be a dirty carb. tomorrow i will take it off and clean it and see if that helps. if so i will stop back and let you know.
thanks

 

[slomo]

Cool weather will need a little choke action.

 

[corvairbob]

no not yet but i will check it tomorrow. but as clean as it is i'm not expectiong anything in the shroud area, but if i find something i sure will clean that out. but after watching those videos i'm really leaning on the carb being dirty.
thanks

 

[slomo]

no not yet but i will check it tomorrow. but as clean as it is i'm not expectiong anything in the shroud area, but if i find something i sure will clean that out. but after watching those videos i'm really leaning on the carb being dirty.
thanks

Pull the metal engine cover off. Inspect the cooling fins and all around the block. Should look like a naked new engine. As in CLEAN!!

 

[sgkent]

A misfire can happen at idle or under a load. It can be caused by air to fuel issues, compression issues, or electrical issues. I would not be in a hurry to work on it until you know what the issue actually is. Run a compression test on each cylinder to see how equal they are, change the plugs, inspect the plug wires for signs of chafing or carbon tracking. I like to check engine plug wires at night by spraying a lite mist of water on them and see if any start arcing. A sticky valve can cause it too, or a leaky head gasket.

 

[corvairbob]

all it was, was a dirty carb. nothing else. i figured it was based on it having power and when i pulled one plug wire at a time it did not reduce rpm's much for each side. it did not smoke or sputter. and i did not get a poke from the wires when grabbing them so the wires are ok. but because i had to choke it i kind fof figured the carb may have been dirty. but was hoping would have gotten some confirmation here. but anyway it runs well. and for 150$ it is a dandy machine. here is what i found engine was not full of debris bowl had junk in the bottom and in the main jet and the idle ports one was plugged just like the YT videos showed. thanks for the ideas but i kind of figured the carb was the culprit.