hey everyone I am Will currently active duty Air Force and I joined this forum because I have a 73 sportster that I have been racking my brain over. The heads were worked on and i threw them on with new gaskets. the whole shibang. I also rebuilt and reset my S&S super E Carb. Now I don't know what to do. the compression check is good, there is plenty of gas going through the carb and there is spark from the plugs. I will get some back fire and the occasional fire out of the tail pipes. Im also rocking a 2000 ignition system. which checked good. I have also have checked this out as well and there seems to be no problem with any of that. If anyone can help I would love to get this bad boy running before the seasons over. Any help would be awesome I would grateful for any feed back. Thank you and have a nice day

SSgt Skags
421 Black Widows

 

Probably didn't line up the cam gears properly.

 

Well, it sure seems like you have covered all the bases. Was the bike running before this work was done? Did you have one or more of the cam gears out of the engine?

How about the shop or person who worked on the heads? What was the problem and what did they do?

I have no experience with S&S carbs but i have refurbished many, of a few different brands. I have often had to go thru a carb two or more times to get it done right. Do you have a little or a lot of experience refurbishing carbs? I understand that the S&S website has explicit instructions for initial carb jetting. Did you use these spec's?

What were the compression numbers. Obviously they were done on a cold engine so they will be quite low, but it is still a useful piece of information.

Is this an XLH [electric start] or XLCH [kick only]?

Backfire/flames out the exhaust sounds may be the key to the problem. It is like the plug is firing when the exhaust valve is open, or unburned exhaust is igniting in hot exhaust pipes. Does this occasional event happen when the pipes are cold? Cold pipes should not ignite unburned exhaust so this may tell you if the problem may be ignition timing or cam timing. If the bike was running before the refurbish and if the cams were not out then it is probably not a cam issue.

I am not saying that it is one of these two things for sure, but it is worth investigating both.