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what causes backfire |
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proc 
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Joined: February-22-2011 Location: westlake Status: Offline Points: 87 |
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 Topic: what causes backfirePosted: July-11-2023 at 2:05pm |
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what causes backfire on first start up after the boat as been sitting at dock for 1-2 weeks without being started. any tips to look for or do before first start up? i pump throttle 2-3 times while turning the key. is that right? any helps is appreciated. i blew entire side off my muffler last week because of backfire.
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67 ski nat
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Joined: July-19-2018 Location: Santa rosa Status: Offline Points: 1194 |
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Posted: July-11-2023 at 5:15pm |
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Backfire is when Fire happens at wrong time. Check timing ??
Have you tried NOT pumping throttle , so less gas to explode Worn valves Let’s see what mrmcd and Ken say |
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proc
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Joined: February-22-2011 Location: westlake Status: Offline Points: 87 |
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Posted: July-11-2023 at 10:42pm |
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Only happens when boat hasn’t been started in a week or so i sometimes try no throttle pump but it just doesn’t turn over. After it starts it starts super easy. Just seems when it’s been sitting for awhile it’s real hard to start. Great to know what’s best way to start first time after sitting for awhile thanks
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11127 |
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Posted: July-12-2023 at 7:03am |
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Well, you're not the first one to blow an Invertaflow apart
Did it backfire every time you started it after it sat for a week or just this one time? How do you start it when it sits overnight? It seems like everybody has their own carburetor priming/starting procedure A couple pumps of the throttle, pull it back to idle or maybe cracked open just a little works for me and if doesn't start, give it another pump or 2 and turn the key again. You may have to do this a few times if the bowl drained down over the week and there's no gas in it for the accelerator pump If over the week, your primary bowl drains down due to some internal leakage, it'll take some cranking for the fuel pump to fill the bowl again When you get to the boat after it sits for a week, take the flame arrestor off, prop open the choke so you can see down the primaries and pump the throttle a couple of times and see if gas shoots out or if nothing shoots out. That'll tell you if the bowl drained down or if had some gas in it for the accelerator pump
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proc
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Joined: February-22-2011 Location: westlake Status: Offline Points: 87 |
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Posted: July-12-2023 at 9:57pm |
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Haven’t been using the boat much so it sits for a week or two so I think there’s no gas in the carburetor. I’ll open it up and take a look next time i start it. I think I’m giving it too much gas on starting it that backfire really scared me. blew the whole side of the muffler off sound like an M 80. Think I woke the entire neighborhood up.
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proc
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Posted: July-12-2023 at 10:00pm |
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Just to be clear you want gas in the float bowl before starting correct?
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proc
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Posted: July-12-2023 at 10:06pm |
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Quick shot of carb cleaner after it has been sitting for a week or so? After first hard start it turns over on a dime every time
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67 ski nat
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Posted: July-12-2023 at 10:38pm |
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Spraying stuff down your carb is not great idea apparently. Ignites and blows up too. Only for lawn mowers
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proc
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Posted: July-12-2023 at 11:03pm |
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Good to know thank you!
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11127 |
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Posted: July-13-2023 at 5:04am |
If that's what it takes.....................there's nothing wrong with that. A squeeze bottle with some regular ol" gasoline will do the same thing. About an ounce worth of "squirt". You might have to repeat it a couple of times. You're just doing the same thing as your accelerator pump would be doing if the bowl was full. Just put the flame arrestor on before you turn the key. After a long winter layup, it's ta good way to get the engine started quickly without a bunch of excessive cranking and if after a week, your bowl is drained, it'll get you started quickly. it's also your best friend when putting a rebuilt or new carburetor on the engine with no gas in the carburetor, or if you ran the boat out of gas it gets you started again without a bunch of cranking  I purposely didn't mention starting fluid because too many people get too excited and start to argue over whether a quick squirt of that will do things like wash all the oil off the cylinder walls or blow your engine to bits Carb cleaner or gas work just fine. Might be a little bit of a "band aid" but if it runs good otherwise, you're up and running and know you have an internal leakage issue and a carburetor rebuild somewhere in your future.
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proc wrote: