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Unread 04-19-2004, 06:03 PM   #1
Baloo
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Help, 258 backfiring out of exhaust ?!

Hello. My 258 just started backfiring out of the exhaust a couple days ago. I havent driven it since then. When I crank it, it even backfires when idleing. I've tried adjusting the idle and mixture screws on the carb, but that doesn't work. I just don't have a clue. I'm learning as I go here and I haven't come across this yet.

Thanks,

Elliott

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Unread 04-19-2004, 11:06 PM   #2
Orange Juice
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Quote:
Originally Posted by Baloo
Hello. My 258 just started backfiring out of the exhaust a couple days ago. I havent driven it since then. When I crank it, it even backfires when idleing. I've tried adjusting the idle and mixture screws on the carb, but that doesn't work. I just don't have a clue. I'm learning as I go here and I haven't come across this yet.

Thanks,

Elliott
Possibly a piece of carbon between exhaust valve seat and face. This would keep valve from being able to shut completely. You can get a fuel additive that will clean fuel system and valves. Don't know if it will work but it won't hurt anything.

To eliminate the carb as the problem, slowly close choke (by hand)while idleing and see if it stops or gets worse. If you are getting a backfire due to a lean condition of the carb, this should temporarily richen it up and cause it to stop.
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Unread 04-20-2004, 12:40 PM   #3
Columbia04
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Have you tried messing with the distributer yet? The timing is pretty easy to check.
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Unread 04-20-2004, 01:04 PM   #4
Baloo
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I got some of that valvoline fuel system cleaner stuff today. I plan on dumping that into the tank tonight. Then check the spark plugs. I will probably have to check the timing too. Just keep em coming guys...You list it, I'll check it until the problem is solved. I just hope it's something external and simple.

Thanks
E
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Unread 04-21-2004, 02:53 PM   #5
Baloo
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An observation that may help someone diagnose this is that it only starts the farting, burping and backfiring when it is warmed up.

E
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Unread 04-21-2004, 06:34 PM   #6
Baloo
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I checked the timing today and it was below zero!!! I bumped it up to 5 and I am going to bump it up a little more tomorrow.

Also, when I put my hand over the carb the idle speeds way up and it runs really smoothe. When I remove my hand it slows way down and idles roughly. What are your thoughts on this???

Thanks

E
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Unread 04-22-2004, 07:06 PM   #7
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Good News!

Good news! I finally got it fixed. I advanced the timing to 7 and reset the carb by reducing the idle (to tractor speed) and adjusting the mixture screws to sound, then readjusted the idle. Runs SMOOOOOTHE. I can actually idle at 600 now without it studdering when I hit the gas. I noticed that the distributor cap and rotor have some wear, so I will get new ones tomorrow. Ah, I also ran some valvoline fuel treatment and a full tank of 93 octane. Don't know whether it was one of the things or a combination of all of them that fixed it. It's time for a washy washy now. Its been sitting so long its got about 3 inches of pollen on it.

E
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Unread 04-23-2004, 07:04 PM   #8
laybackman
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Quote:
Originally Posted by Baloo
Good news! I finally got it fixed. I advanced the timing to 7 and reset the carb by reducing the idle (to tractor speed) and adjusting the mixture screws to sound, then readjusted the idle. Runs SMOOOOOTHE. I can actually idle at 600 now without it studdering when I hit the gas. I noticed that the distributor cap and rotor have some wear, so I will get new ones tomorrow. Ah, I also ran some valvoline fuel treatment and a full tank of 93 octane. Don't know whether it was one of the things or a combination of all of them that fixed it. It's time for a washy washy now. Its been sitting so long its got about 3 inches of pollen on it.

E
Good show! You were trying to fix a timing problem by adjusting the carb. The best part is that you discovered it yourself. You won't forget that one!
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