QuestionQUESTION: I ride my 1970 XLCH down an 18 mile long country road to get into town each day. I usually cruise at about 60mph. Many times now, about a third of the way into my trip, it will seem as though I am losing power, the bike will begin backfiring and bucking and shooting flames, and the sound will change. It will sound almost like an old electric sewing machine - a kind of rapid rhythmic mechanical clank instead of the deep industrial sounding happy clunk that old ironheads usually produce. If I slow down a bit, maybe downshift and coast a little, or pull off the road and sit for a minute with the bike off or even just idling, I can take right off and go like it never even had a problem. The bike doesn't stall, it just loses it's oomph for a sec and backfires, once twice, several times. I can get up to cruising speed, cruise for awhile, and it may happen again before the end of the road - sometimes, but not always. This road is the only part of my 40 mile trip into work that gives me a problem - but it's also the only road where I routinely exceed 45 mph - I can't help but think that is a clue somehow. I'm in coastal Georgia so the road is pretty flat. The bike is in excellent condition overall, we've done a LOT of work to it, and I keep it very clean. I have no oil leaking from anywhere, really!, and the bike seems to be getting adequate fuel and spark. I checked the seals at the intake and no air seems to be getting in. I have an SS super e carb, and I had a very competent friend make sure that it was adjusted correctly. This problem is driving me crazy. It's not gotten better or worse over time - it started happening intermittently last spring, and continues to happen at random - sometimes I will get back & forth to work without ever experiencing the problem. Since the problem began, I have rebuilt the top end, replaced the clutch, installed an electronic ignition (not factory spec), replaced coil, cables, points, wires, battery, and this problem has survived it all! I know I must be damaging something every time I ride to town, but I can't figure out what it might be! I would be very grateful for your help. Thanks!
ANSWER: Close to the end of your question you said what you have replaced. You said the electronic ignition and then said the points. Are you running points or electronic igntition?
Mike
---------- FOLLOW-UP ----------
Melissa's Sportster
QUESTION: Thank you for responding so quickly! I meant to say that I had an electric starter, not an electronic ignition! Given the difference, I'm not quite sure what I was thinking there, sorry for the confusion! Melissa
ANSWER: First, pull the plugs and let me know what color they are. When you replaced the points, did you also replace the condenser?
Mike
---------- FOLLOW-UP ----------
QUESTION: The front plug just looks kind of grayish, but the rear plug is black, and a friend who was riding behind me today did see flames coming out of the top pipe this time. I know my experience is limited, but I keep thinking it has to be a timing problem. I have followed the manual so precisely though, and taken SO much care to get it all just right...the advance seems to be set properly and the points are functioning just like they are supposed to. I did replace the condenser when I changed the points - it didn't seem to make a difference.
AnswerYour plugs should be a tan color. Since your rear plug is black then your rear cylinder is not burning correctly with is probably causing your problem. You changed your coil and plug wires so that would not be the problem, but I would still test them. If the black plug is oily then you are burning oil in that cylinder and fouling the plug.
Good luck and happy riding
Mike
