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 Motor Shutting of at full throttle 
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Joined: Thu Sep 05, 2013 6:11 pm
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Post Motor Shutting of at full throttle
Hey guys, I have 95 hours on a stock 2013 23hp B&S Vanguard on a copperhead frame. Although I know it's not recommended, I've always run ethanol gas with no problems, as I always run it dry (fuel line and all) if storing for more than two weeks. Well, I slipped up on that rule and let it sit for 5 weeks without running gas out of the fuel line and carb. Took it out a few days ago , and it cranked fine, ran smooth as butter, and got up to full speed, but would conk out immediately after about 20 seconds of running above 3000 rpm. Limped back to the ramp at half throttle. I took apart the whole fuel line and rain air through all sections, and interior hose line seems to be in good conditon. Talked to Gil at copperhead and although he couldnt say for sure, he said they changed fuel pumps every 20-30ish hours on these motors and I'm on the orignal one at 95 hours. The pump works off a vacuum created by crankcase pressure I believe. I'm replacing original fuel filter and pump that came with it. Do yall think this is the issue, or do I have a bigger problem with internals or carb.

Thank you all for your time.


Fri Apr 20, 2018 1:29 pm
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Post Re: Motor Shutting of at full throttle
I would clean the carb. You can pull the fuel line from the carb and put it in a bottle or something to catch the gas and spin the engine over to check the flow from the fuel pump.


Fri Apr 20, 2018 7:03 pm
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Post Re: Motor Shutting of at full throttle
Although a dirty carb is very possible usually the first thing on a carb to get plugged up is the idle circuit since it's the smallest orfice. Your idles good so your carb might be ok. Start with the fuel pump as they said. They are cheapies so buy 2 at a time. You could have verified a failed a failed pump by pumping the bulb while you were running. Even if it's a carb clean, new pump and new fuel line it's still a minor job


Sat Apr 21, 2018 10:35 am
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Post Re: Motor Shutting of at full throttle
Your tank properly vented? I have one of those shitty EPA tanks, so I always unscrew the cap to get a good vent. Leave the cap on barely threaded. Go ahead and change the fuel pump since they are so cheap, but I've never heard of that being a part that gets changed as regularly as Gill said. I had one fail at around 300 hours on my old motor.


Sat Apr 21, 2018 12:04 pm
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Post Re: Motor Shutting of at full throttle
Might check your oil level and oil pressure safety switch, also.


Sat Apr 21, 2018 3:00 pm
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Location: Trinity Bay - Texas
Post Re: Motor Shutting of at full throttle
eliminate fuel supply issues by pumping bulb manually...

larger diameter fuel lines like 5/8 often cause trouble go smaller...

seafoam in some premium chevron will help clean carb...

consider running ONLY chevron premium - techron liquid additive runs cleaner
than white powder additive many fuels use to achieve emissions standards...

then put in new plugs and look for any difference visually from one to another
as fouled plug is more likely than bad fuel pump...

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Sun Apr 22, 2018 5:31 am
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Post Re: Motor Shutting of at full throttle
Thanks for the replies guys. To hit a couple points mentioned above: I've actually drilled out the vent "screw" on the gas cap because it's a crappy new EPA tank that doesn't even vent. But, just to play it safe, I took the whole gas cap off as I was running as to eliminate the venting issue. I also held the primer bulb in my hand and pumped it manually every 2-5 seconds, and although it helped, the motor still cut off. That's why I'm not sold that the fuel pump is the issue. As yall mentioned though, the fuel pump and filter are cheap so I'm replacing those. My thought is that if the carb was gummed, it wouldn't crank so well or run so well for the first 20-30 seconds before it dies. Thanks for all the help.


Sun Apr 22, 2018 4:45 pm
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Post Re: Motor Shutting of at full throttle
Update: Replaced fuel pump, fuel filter, spark plugs, and oil/oil filter. Runs like a top again. My bet is the fuel pump or fuel filter was bad.


Tue Apr 24, 2018 7:32 pm
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