Need help with backfire
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5th Gear
Joined: Apr 2006
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Need help with backfire
My wife has a 87 Softtail trike. Her late husband designed and built the rear end. It has a S&S carb that has been rejetted to handle the heavier load. What jetting, I have no idea. The back firing happens on acceleration, normally at 60 to 70 mph. Happens with a little or a lot of twist on the throttle. It is worse on colder days. I have seen flames come out the exhaust pipes, and sometimes it looks like the whole electrical system has shut off and comes right back on, in conjuction with the backfire. I have installed new plugs, wires and coil to no effect. Only once did it backfire on deceleration. It has a smooth idle and starts right up. I have no idea what to look for from here. Any ideas? Thanks in advance!
Tourer
Joined: May 2006
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RE: Need help with backfire
Does the exhaust have baffles installed? If not, then put some in or you'll never get it tuned right. Also check for exhaust leaks. That usually causes popping out the pipes. Replace the exhaust gaskets at the heads and torque them as per the factory service manual. Then attach and torque the mounting brackets. ALWAYS torque at the head first, and if the brackets don't line up, bend or shim them until they do. Don't try to move the pipes or they may leak at the head.
Once you have done that, put it on a dyno and get it tuned properly. I don't know of many who can test trikes, but they can at least hook up the AFR meter to check your mixture. You could spend days trying to get it right "by ear" or by reading plugs. It can be done, but it's a lengthy process that requires an open, empty road, several sets of new plugs, several high speed runs, and a lot of patience. If it is the jetting in your case, then it'll be in the high-speed circuit, which makes using an AFR meter even more necessary.
Once you have done that, put it on a dyno and get it tuned properly. I don't know of many who can test trikes, but they can at least hook up the AFR meter to check your mixture. You could spend days trying to get it right "by ear" or by reading plugs. It can be done, but it's a lengthy process that requires an open, empty road, several sets of new plugs, several high speed runs, and a lot of patience. If it is the jetting in your case, then it'll be in the high-speed circuit, which makes using an AFR meter even more necessary.
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5th Gear
Joined: Apr 2006
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RE: Need help with backfire
I thank those who have given a response to my problem. I haven't had a chance to work on her bike yet due to other problems that have come up like a broken garage door opener, and other such things! I will reply again when I have had a chance to work on it. Thanks again! Nick with the Wide Glide.
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