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18 hp B&S needs full choke


toomuchgrass's Avatar
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Join Date: Aug 2006
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08-23-06, 09:27 PM   #1  
18 hp B&S needs full choke

Hello all,

I have a 18 hp twin II model 422707 engine. Last year, it had a bad case of hunting and would only run if it was choked at least 80%. So I got a carb kit and rebuilt the carb. The hunting got a little better and it would run at between 30& to 50% choke. Perhaps a partial success.

This year, the hunting has not gotten worse but it has required more and more choke until it only ran at 100% choke. If I back off the choke just a hair (the movement of the plate is barely perceptable), the engine stops at any RPM except idle. It doesn't run at all at idle. It deterioated further in that it will now only run for 10 to 15 seconds before stopping.

From reading other posts, it seems like I need to clean/rebuild the carb again. Obviously, I missed something last time and I would like to get anyone's opinion as to what it could have been. I completely disassembled it and soaked it in carb cleaner but I didn't remove any welch plugs (if they were ther - I just learned what they were tonight). I also blew it out with compressed air.

Any suggestions as to where to focus would be greatly appreciated. Sorry for being so long winded.

Thanks.

 
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cheese's Avatar
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08-23-06, 09:45 PM   #2  
You're right in your diagnosis. I would first attempt repair with the carb still on the machine. Remove the top of the carb, remove the drain plug, and clean out the bowl well. Then you can access the main jet through the drain plug hole. If the carb has a metal float, the main jet is removed with an allen wrench. If it has a plastic float, the jet fits a flathead screwdriver. Get the jet out and clean it well and clean the area behind it well. Blow out with compressed air and give it a shot. This works on better than 90% of the opposed twin briggs carbs I work on. If it doesn't work, time to clean it in a bath type carb cleaner.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
toomuchgrass's Avatar
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Join Date: Aug 2006
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08-25-06, 07:29 PM   #3  
Thanks for the reply, cheese.

Last weekend I did almost what you suggested. I took the top off and removed the drain plug and took out the main jet. I didn't blow it out with compressed air though. I just looked at it. There was a small amount of a gooey substance in the fuel pump housing. I think I'll try to overhaul the carb again.

I got the carb kit today and it has a welch plug in it. Are these hard to replace? any tips?

Thanks

 
cheese's Avatar
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08-25-06, 09:18 PM   #4  
They can be tricky sometimes. I suggest saving that as a last resort. A carb can be successfully cleaned without welch plug removal almost every time.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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