rear cylinder not firing
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Stage II
Joined: Aug 2018
Posts: 2
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From: central coast
rear cylinder not firing
98 sportster 883, limped home on front cylinder. have spark to rear but was weak so replaced plugs and coil. have spark still not firing. possible causes/ issues?
Sounds like the same issue I had recently on my old '86 Intruder. After replacing the coils and plug wires the issue remained, no ignition on the back cylinder. Feeling that the pipe and exhaust on that cylinder was not getting that hot pointed me in the direction of a clogged rear carb.
Not sure how the Sportster is setup, but the Inturder has separate intake boxes and air filters for each cylinder. I was able to spray some starter fluid in the rear cylinder intake box and that cylinder fired up for as long as the starter fluid lasted, confirming it was a fuel delivery issue.
I was lucky and lots of Berryman's B-12 sprayed into all passages and Seafoam in the tank, then letting it sit for a long while avoided a carb rebuild for me. Your mileage may vary. Note - I used some thin fishing line to poke in the openings I could in combo with the carb cleaners. It may come down to you needing to pull carbs for a cleaning.
Not sure how the Sportster is setup, but the Inturder has separate intake boxes and air filters for each cylinder. I was able to spray some starter fluid in the rear cylinder intake box and that cylinder fired up for as long as the starter fluid lasted, confirming it was a fuel delivery issue.
I was lucky and lots of Berryman's B-12 sprayed into all passages and Seafoam in the tank, then letting it sit for a long while avoided a carb rebuild for me. Your mileage may vary. Note - I used some thin fishing line to poke in the openings I could in combo with the carb cleaners. It may come down to you needing to pull carbs for a cleaning.
Last edited by Redd Jedd; Aug 25, 2018 at 03:27 PM.
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Joined: Jan 2007
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From: along the shore of Mishigami
Check the ground wire cable to the starter and to the frame, I had a '99 XLCH 1200, did some weird crap while running and found the cable inside the lug/terminal had corroded and operating on three strands.
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Joined: Aug 2008
Posts: 22,848
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From: Lafayette, Louisiana
Originally Posted by Redd Jedd
Sounds like the same issue I had recently on my old '86 Intruder. After replacing the coils and plug wires the issue remained, no ignition on the back cylinder. Feeling that the pipe and exhaust on that cylinder was not getting that hot pointed me in the direction of a clogged rear carb.
Not sure how the Sportster is setup, but the Inturder has separate intake boxes and air filters for each cylinder. I was able to spray some starter fluid in the rear cylinder intake box and that cylinder fired up for as long as the starter fluid lasted, confirming it was a fuel delivery issue.
I was lucky and lots of Berryman's B-12 sprayed into all passages and Seafoam in the tank, then letting it sit for a long while avoided a carb rebuild for me. Your mileage may vary. Note - I used some thin fishing line to poke in the openings I could in combo with the carb cleaners. It may come down to you needing to pull carbs for a cleaning.
Not sure how the Sportster is setup, but the Inturder has separate intake boxes and air filters for each cylinder. I was able to spray some starter fluid in the rear cylinder intake box and that cylinder fired up for as long as the starter fluid lasted, confirming it was a fuel delivery issue.
I was lucky and lots of Berryman's B-12 sprayed into all passages and Seafoam in the tank, then letting it sit for a long while avoided a carb rebuild for me. Your mileage may vary. Note - I used some thin fishing line to poke in the openings I could in combo with the carb cleaners. It may come down to you needing to pull carbs for a cleaning.
Road Master
Joined: Jan 2009
Posts: 804
Likes: 105
From: Charlotte, NC/Greenville, SC
For combustion you need spark and fuel. If you have good fire at the plug electrode and plenty of gas your problem may be a bad head gasket. To narrow it down do a compression check.
Last edited by motohaid; Aug 26, 2018 at 10:59 AM.
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Joined: Sep 2012
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From: USA
I got a 1980 thousand cc custom Sportster with a S&S Super E and a Crane Cams ignition.The engine vibrated a lot and there were a lot of pops out the carburetor. I had to fight with trying to get the right jets. Once I got some used a lot in a couple large towns at the same elevation and a set of stock exhaust pipes and they did not solve the problem I had to study the carburetor manual further. Since it said the problem could be the ignition I checked it out. Wile doing so I found out the end of the spark plug wire that plugs into the coil had come apart. I ad to mess with it until it no longer comes apart. next I got a bunch of white smoke that smelled like gas coming out the front exhaust pie after cold starts that went away. That made me use some B-12 which got rid of the smoke. Finally I figured out that the gas caused the smoke and found a local station that sells Phillips 66.Now my bike has mostly lost pops out the carburetor and once warmed up runs like a race bike. portster with a S&S Super E and a crane cams ignition.
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Last edited by nucklehead13; Dec 19, 2018 at 09:34 PM.
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