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Back Firing

21593 Views 19 Replies 12 Participants Last post by  Dawg Fan
When i am goin full throttle and i let off and gear down my honda backfires. Also when i turn it off it back fires and they are pretty loud. How Would i fix this ?
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We remove the pilot screw , clean the carbon (black) off the tip , install and re-adjust ..
My wifes 400 did this all the time. Muffler had baffles gone in it, replaced it with a new one and has been perfect since.
My weeler dose the same thing ,but only wen i slow down , i found a crack in mannifold on exhaust but ive never actually taken exhuast pipe and muffler off ,
QUOTE ("shaun.1089":2bp648ue)
When i am goin full throttle and i let off and gear down my honda backfires. Also when i turn it off it back fires and they are pretty loud. How Would i fix this ?
Hi just to let you know I had a foreman 400 new in 1996 and it backfired really really loud, you would want to wear ear plugs when it backfires it was that loud, from the first day I had it. Then I put on about 12,000km on it and had to replace the muffler and it backfired a little bit. The honda dealer says it is common for the 400. Maybe an aftermarket exhaust will solve the problem. I now have a foreman 450 not much difference but the seat is higher.
Yes it's common with the TRX400FW .. Clean the black carbon off the tip of the air/pilot screw .. The problem is a lean missfire caused by carbon (black) on the tip of the air screw ..
havin the same problem of backfiring when leting off or gearing down.
had a frend look at it no exhoust leak, valves ajusted, new air breather, and carburator taken apart and cleaned thouroghly.still it backfires.
sitting still rev it up hard let off then hit gas twice real quik and letting go will backfire every time. please help dont know what to check next.
QUOTE (Honda Mechanic @ Jul 31 2007, 09:36 AM) index.php?act=findpost&pid=81065
We remove the pilot screw , clean the carbon (black) off the tip , install and re-adjust ..
I have a 96 foreman 400 was running bad cleaned carb 3 times idles better now surges when you throttle dont know a whole lot bout wheelers but fast learner please help wife and kids wanna go riding also the carb is spitting gas out the breather side is this a timing issue or carb
QUOTE (chevy_dad07 @ Sep 14 2009, 04:35 PM) index.php?act=findpost&pid=135062
I have a 96 foreman 400 was running bad cleaned carb 3 times idles better now surges when you throttle dont know a whole lot bout wheelers but fast learner please help wife and kids wanna go riding also the carb is spitting gas out the breather side is this a timing issue or carb
This could possibly be timing or the valves need adjusted.Also I would check carb slide diafram for surging
QUOTE (4wsteve @ Sep 15 2009, 12:39 AM) index.php?act=findpost&pid=135069
This could possibly be timing or the valves need adjusted.Also I would check carb slide diafram for surging
adjusted valves spring was missing on top of vacum diafram runs alot better idles good no surging still has bad back fire when reved and let off backfires out exhaust then carb still spraying gas out of carb is this typical?
QUOTE (chevy_dad07 @ Sep 17 2009, 05:25 PM) index.php?act=findpost&pid=135236
adjusted valves spring was missing on top of vacum diafram runs alot better idles good no surging still has bad back fire when reved and let off backfires out exhaust then carb still spraying gas out of carb is this typical?
I don't think it should spray gas out the carb but I never checked. Do you have an air filter on it?
You may need to richen the needle=idle mixture screw
Also check for exhaust leak
QUOTE (4wsteve @ Sep 18 2009, 12:37 AM) index.php?act=findpost&pid=135251
I don't think it should spray gas out the carb but I never checked. Do you have an air filter on it?
You may need to richen the needle=idle mixture screw
Also check for exhaust leak
ok here is a new tid it does have a small exaust leak at the head tightened bolts got little better with the air box off it runs like a top put the breather and box back on starts surging again
QUOTE (chevy_dad07 @ Sep 18 2009, 05:22 PM) index.php?act=findpost&pid=135300
ok here is a new tid it does have a small exaust leak at the head tightened bolts got little better with the air box off it runs like a top put the breather and box back on starts surging again
Did you install the proper spring in the carb? Did you do anything to richen the carb?
You need to tune it with the air box on for it to run properly with the air box on!
QUOTE (shaun.1089 @ Jul 31 2007, 12:53 AM) index.php?act=findpost&pid=81062
When i am goin full throttle and i let off and gear down my honda backfires. Also when i turn it off it back fires and they are pretty loud. How Would i fix this ?
MY 450 does that I put a new plug in it set the jets ajust the valves put carb cleaner in it i will ckeck the exhaust mine back fires very loud like a gun going off
well i put a new seal on the exaust put a new plug in it ajust the valves put carb cleaner in it
and it still backfires what else can I do ? :rant
QUOTE (a676man @ Oct 10 2009, 10:12 AM) index.php?act=findpost&pid=136558
well i put a new seal on the exaust put a new plug in it ajust the valves put carb cleaner in it
and it still backfires what else can I do ? :rant
Maybe you need to adjust the fuel mixture screw? And also it might help to take
the screw out and clean the tip. Then put the screw about 2 and 1/2 turns out or maybe 3
QUOTE (4wsteve @ Oct 10 2009, 12:17 PM) index.php?act=findpost&pid=136564
Maybe you need to adjust the fuel mixture screw? And also it might help to take
the screw out and clean the tip. Then put the screw about 2 and 1/2 turns out or maybe 3
Thanks I will try that
hello all
i know this is old post so sorry for draging it back ,
But did any of you guys get to bottom of 450 backfire ?????
i know it could be one of many small things causeing this did cleaning you pilot jet help ?
My foreman 450 does same when you rev or race it hard and then wind down to stop BANG
(would scare the **** out of you if you didnt expect it not much good for going shooting !!! every thing scared away ! )
The atv run great other wise may be wee bit hard to start when cold my old 300 started firs time all the time but when started its fine to start after so

Please any clues where next Honda dealer thinks mite be choke sticking have checked seems ok mite replace it its not to dear
drive it harder, and just think people are shooting at you.
check to make sure that the drain cap on the bottom of the airbox is on good. That caused my forman to backfire.
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