Backfire - Why?

skarp · 02-23-2011, 03:13 PM

Sounds like the airbox is not sealed up...my G2 backfired because of this!

Stephen

stuff4mason · 02-23-2011, 03:49 PM

Yea, the airbox is sealed. I purchased new rubber tabs all the way around it. What is weird is that I found a small split in the muffler at the weld to the header, that wasn't there a few days before. So, I welded it up tight. Today, I took the cart out and it still was backfiring. When I got it back in the garage, a NEW split showed up below (different angle) between the muffler and header. Is there a possiblity that somehow the baffle is plugging the muffler exit hole, and creating all kinds of pressure in there?

stuff4mason · 02-23-2011, 04:07 PM

Just called our local yami cart part supplier. He says that muffler is $278.00....***! He also says it could have so much carbon buildup, its blowing out at its weakest points. $278, I might as well keep letting it backfire. The wife isn't going to let me spend that! Are there any other alternitives? Does anyone have one of these laying around in good shape?

sho305 · 02-23-2011, 04:18 PM

You can buy lawn mufflers for <50 all over, just chop the header off and mount to new muffler for 12hp or more. I'm going to run a car muffler on my clone 16hp to keep it quiet. Actually I could sell you a muffler missing the header that worked fine, but I can't get to it now. Poke wire in there and see what is up. Cut the outlet pipe off and poke something in there. This guy modified his but you get the idea. He cut up the tailpipe and put double the pipes inside. I'm not sure how one would plug like a G1, the 2 stroke oil plugs those. If you hold the seat up I think you can run it without the muffler at all and see if it backfires.

I've seen cheaper on closeouts, but here is a B&S

Amazon.com: Lawn Mower MUFFLER (FOR 1-1/4"OD PIPE)B&S Replaces BUNTON-GOODALL 252762: Home & Garden

stuff4mason · 02-23-2011, 06:11 PM

My old eyes are playing tricks on me. Brought the cart out into the sunshine and realized, it wasn't cracked. I was seeing a peice of welding wire!! I ran the engine in neutrual and felt around the exhaust. It doesn't seem to be leaking anywhere. Took the air cleaner off and found a small amount of oil in the bottom. As Skarp mentioned above, I think he might be right. The air cleaner lid was not on perfectly. I got it to kinda 'snap' into place. Think its locked down now. Cleaned that out, adjusted the fuel mixture back to 1 1/4 turns out. Also tightened the engine tentioner a bit more. I drove it around with no body or seat so I could watch everything. (I don't recommend this!!) First of all, the cart hauled a$$! Its spinning dirt now! It did slightly backfire, but it was more of a big puuuf, instead of BANG! Its weird though. Sounded like it was back firing through the carb. Not sure why there was oil in the air cleaner, except maybe I added a hair too much when I changed it. Now that its lifted the engine may be spitting out the extra. I think the clutches are perfect now.

skarp · 02-23-2011, 07:17 PM

Oil in the airbox means you over filled it. They hold exactly one quart!!! My g2 had the factory wrong dipstick. One quart only Percilly....one quart only! That is my "Hint for Red October" impression!

sho305 · 02-23-2011, 07:28 PM

One quart, the stick will read around half once you lift the cart, put one quart in and mark the stick as full.

Check the airbox again make sure its right, we all know it can be a pita and that rubber thing can get twisted too. Turn the idle mix another 1/8-1/4 open if it pops on slowdown. It should not miss when you give it gas.

02-23-2011, 03:13 PM	#11
skarp Gone Wild Join Date: Nov 2009 Posts: 250	Re: Backfire - Why? Sounds like the airbox is not sealed up...my G2 backfired because of this! Stephen
skarp Gone Wild Join Date: Nov 2009 Posts: 250

02-23-2011, 03:49 PM	#12
stuff4mason G8 Club Founding Member Join Date: Sep 2010 Location: Middle of Virginia, USA Posts: 4,265	Re: Backfire - Why? Yea, the airbox is sealed. I purchased new rubber tabs all the way around it. What is weird is that I found a small split in the muffler at the weld to the header, that wasn't there a few days before. So, I welded it up tight. Today, I took the cart out and it still was backfiring. When I got it back in the garage, a NEW split showed up below (different angle) between the muffler and header. Is there a possiblity that somehow the baffle is plugging the muffler exit hole, and creating all kinds of pressure in there?

02-23-2011, 04:07 PM	#13
stuff4mason G8 Club Founding Member Join Date: Sep 2010 Location: Middle of Virginia, USA Posts: 4,265	Re: Backfire - Why? Just called our local yami cart part supplier. He says that muffler is $278.00....***! He also says it could have so much carbon buildup, its blowing out at its weakest points. $278, I might as well keep letting it backfire. The wife isn't going to let me spend that! Are there any other alternitives? Does anyone have one of these laying around in good shape?

02-23-2011, 04:18 PM	#14
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Backfire - Why? You can buy lawn mufflers for <50 all over, just chop the header off and mount to new muffler for 12hp or more. I'm going to run a car muffler on my clone 16hp to keep it quiet. Actually I could sell you a muffler missing the header that worked fine, but I can't get to it now. Poke wire in there and see what is up. Cut the outlet pipe off and poke something in there. This guy modified his but you get the idea. He cut up the tailpipe and put double the pipes inside. I'm not sure how one would plug like a G1, the 2 stroke oil plugs those. If you hold the seat up I think you can run it without the muffler at all and see if it backfires. I've seen cheaper on closeouts, but here is a B&S Amazon.com: Lawn Mower MUFFLER (FOR 1-1/4"OD PIPE)B&S Replaces BUNTON-GOODALL 252762: Home & Garden Amazon.com: Lawn Mower MUFFLER (FOR 1-1/4"OD PIPE)B&S Replaces BUNTON-GOODALL 252762: Home & Garden

02-23-2011, 06:11 PM	#15
stuff4mason G8 Club Founding Member Join Date: Sep 2010 Location: Middle of Virginia, USA Posts: 4,265	Re: Backfire - Why? My old eyes are playing tricks on me. Brought the cart out into the sunshine and realized, it wasn't cracked. I was seeing a peice of welding wire!! I ran the engine in neutrual and felt around the exhaust. It doesn't seem to be leaking anywhere. Took the air cleaner off and found a small amount of oil in the bottom. As Skarp mentioned above, I think he might be right. The air cleaner lid was not on perfectly. I got it to kinda 'snap' into place. Think its locked down now. Cleaned that out, adjusted the fuel mixture back to 1 1/4 turns out. Also tightened the engine tentioner a bit more. I drove it around with no body or seat so I could watch everything. (I don't recommend this!!) First of all, the cart hauled a$$! Its spinning dirt now! It did slightly backfire, but it was more of a big puuuf, instead of BANG! Its weird though. Sounded like it was back firing through the carb. Not sure why there was oil in the air cleaner, except maybe I added a hair too much when I changed it. Now that its lifted the engine may be spitting out the extra. I think the clutches are perfect now. Last edited by stuff4mason; 02-23-2011 at 06:13 PM.. Reason: cause it needed editing!

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02-23-2011, 07:17 PM	#16
skarp Gone Wild Join Date: Nov 2009 Posts: 250	Re: Backfire - Why? Oil in the airbox means you over filled it. They hold exactly one quart!!! My g2 had the factory wrong dipstick. One quart only Percilly....one quart only! That is my "Hint for Red October" impression!
skarp Gone Wild Join Date: Nov 2009 Posts: 250

02-23-2011, 07:28 PM	#17
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Backfire - Why? One quart, the stick will read around half once you lift the cart, put one quart in and mark the stick as full. Check the airbox again make sure its right, we all know it can be a pita and that rubber thing can get twisted too. Turn the idle mix another 1/8-1/4 open if it pops on slowdown. It should not miss when you give it gas.

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