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Discussion Starter · #1 ·
I hate posting this on urgent cause i'm not sittin on the side of the road, but i need your help/suggestions. My bike has been backfiring "under load". usually in 5th gear about 65-75, when i give it throttle, she coughs and backfires. also seems to vibrate more than normal under those conditions. i took it for a ride this evening and i pushed the choke knob in...pulled it out just a tad then shoved it back in to make sure it was all the way in. it seemed to run a lil better. i'm wondering if my choke could be out just a tad. not to throw anyone off, could be something totally different.
 

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Is the bike stock. We need to know of any changes to the bike/ pipes/air box stock/ re jetted. Always give as much info so we can figure out what is causing it.

Have you checked the ECM wires to see if maybe the green or black wires going into it is broken inside the wire insulation. you need to look very close.

Donut/Doug:patriot:
 

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Discussion Starter · #3 ·
Thanks Donut. Arlen ness big sucker. cobra dragsters (No baffles). its been rejetted. maybe just a coincidence but it ran better when the weather was a lil cooler 70-80 degrees. lately its been around 85-100. not sure if that would matter. keep it mind, it only coughs and backfires in 5th gear going about 65-70 and i give it heavy throttle. thanx for any help. i'll check the wires.
 

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His Excellency
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Do you know the condition of the exhaust crush gaskets? Is there an exhaust leak? Have you checked all the vaccum lines for cracks or impropper fit? Sounds like you are getting air fed back into the exhaust somehow.
 

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the big tip to me sounds like it ran better when it was cooler sounds to rich and now the air is thinner from heat i would back down the air fuel mix .
i don't think texas summers are known for thinner air when it gets hot. atleast not when i've been to tejas in the summer time....i know south carolina summers don't get that way, it's the opposite...humidity up in summer and down in winter :)

it does sound like an a/f problem, but i wouldn't rule out the jet...as for the crush gaskets on the exhaust, i've never experienced load back fire because of crush gaskets, only on decel....
 

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As Charlie D asked above - what jet kit was put in there and by who.
Listen to Charlie D - He is our resident carb man and he is teaching me as wee go lol.

Donut:patriot:
 

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I'm still with shine runner.cold air like at the race track is better more air for the fuel.
while i do agree with you and shinerunner that it ran better in the cooler and thinner air, i don't however agree that summer air is thinner...my reasoning: today it's 96 with humidity of 94 (thick air as you can see it)...january 43 with humidity 46 (brisk and dry) :cheers:
 
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Discussion Starter · #12 ·
Let me start by saying i really do appreciate all ya'lls imput. seriously. i took it to my mechanic today. (retired after15 yrs from the stealership to open his own shop). he builds racing bikes and works on everything from Hondas to Harleys. He was referred by a very reliable friend. I truly feel like he knows what he's doing. But i always like to get an idea from ya'll cause most of ya'll have been there and done that. Since he's rejetted it, it has NEVER backfired on decel. so i figured thats a plus. when he jetted it, it was 27 degrees and low humidity. lately its been 95+ and high humidity. So for him to even get close, i figure he has to be pretty good. i'll get it back tomorrow and let ya'll know the outcome. please don't take this as not appreciating ya'lls ability or knowledge to help. ya'll are a GREAT bunch of guys. i just didn't have confidence in myself to fix it and i want her to run right. thanks again to those of you that help.
 

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when he jetted he set for the temp which was cold and now that it is hot you are very rich.

A lean condition gets better when the temp gos up.
a rich condition gets worse when the temp gos up.

so if he jetted correct for the cold and now it is hot it has gotten richer.
 

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the way i was taught coming up and building hotrods and racecars. cool air is thicker and hotter is thinner. which is why turbos have intercoolers. and you want air from outside of the engine compartment when you are going for the most power. now the air feels thicker when it is hot and humid which there is alot of in columbia SC when i lived there and here in richmond va during the summer. but it is water vapor in the air not oxygen and that is what the air fuel ratio is set off of. 15 parts air to 1 part fuel for cruise and as low as 7 parts air to 1 part air being about as rich as it can run. 15 to 1 gets best milage and 12 to 1 seems to be better for power and anything less then about 9 to 1 starts causeing problems. but that was classes i took a long time ago i might be remembering wrong.
 

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the way i was taught coming up and building hotrods and racecars. cool air is thicker and hotter is thinner. which is why turbos have intercoolers. and you want air from outside of the engine compartment when you are going for the most power. now the air feels thicker when it is hot and humid which there is alot of in columbia SC when i lived there and here in richmond va during the summer. but it is water vapor in the air not oxygen and that is what the air fuel ratio is set off of. 15 parts air to 1 part fuel for cruise and as low as 7 parts air to 1 part air being about as rich as it can run. 15 to 1 gets best milage and 12 to 1 seems to be better for power and anything less then about 9 to 1 starts causeing problems. but that was classes i took a long time ago i might be remembering wrong.
i do stand corrected, as i was in my own world with the humidity (simply cause you can see it in the air) and the oxygen (which you can't see)....but yes, there's more oxygen by volume in cooler air versus the hot air and that is why the bike probably ran better in the cooler air as more fuel with the proper amount of air was being induced...sort of like going from low areas to high areas...it's cooler up there, but with less oxygen and that's why some people get dizzy, nause, vomiting, and seating and some pass out...amazing how cool air has more oxygen person volume, but when you go higher the volume of oxygen decreases as it also gets colder :) when my head is somewhere else, i will admit and apologize...sorry my confusion, but my brain is fried right now with the class load & clinicals and i'm seriously surprised i can think at all to be honest...:cheers:
 

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Discussion Starter · #18 ·
Ok, guys, i found....excuse me....ya'll found the problem. (if i may add a lil humor and fun), Donut, i owe you a bottle of crown, the rest of you well, you get a 12 pack. IT WAS THE BLACK WIRE!!!:banghead:
Got the bike back from my mechanic. took it for about a 50 mile ride with friends. ran good at first, then goin up a hill in 5th gear into a headwind, throttle down and "BAM" backfire. Then shortly after that, we went over a small bridge that was very uneven, kinda like drivin over a pothole, "BAM" backfire. lights came on..:idea:. I said to myself, SLade, that sounds like a short...:hmm2:. Got to my friends house, took the seat off, started it up, wiggled and moved the black and green wire ever so gently, and "BAM", she died...:D. At this point i thought about Donut and Carlie D...I swear i did. In Tow, Texas, population 572, and i was thinking about my brothers on the forum:cheers:. I slowly rotated the black wire around and bingo, exposed wire, about 2 strands still attached. I snipped, crimped wrapped and had the best ride in the Texas Hill Country. Thanks guys
Ps: i called my mechanic, and he said those wires were the very first thing he checked, but now i can see, its not easy to spot as Donut pointed out. Again, thanks alot guys, add another success story to ya'lls portfolio..:mosh::choppersmRide safe
 

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Discussion Starter · #20 ·
Yeah Charlie, shes back to her old self. Thanks for ALL your help. Your one of the guys i'm talking about when i mention all the help ya'll provide on here. Lotta Good Floks on here. Thanks again-Slade
Ps: i will pass along the green/black wire issue. ya'll got that one nailed
 
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