77 sporty

Discussion in 'Sportster Models' started by kdrok, Jul 22, 2011.

  1. kdrok

    kdrok New Member

    I have a 77 sportster that dies when it gets hot. I have eliminated coil, plugs and wires as well as wiring as problems. i reset the timing and points. The flyweights etc are new and ok. It seems to be hard to start as well sometimes. I was wondering if anyone knows what the generator output should be at idle and when revving up to about 2000 rpm. Would it have an effect on the way it runs if it is around 12v charge when running. It seems to backfire a bit before it dies as well. I,m scratching my head on this one so any help would be greatly appreciated. Thanks in advance to anyone who can help me out. Bye for now.
  2. Hoople

    Hoople Account Removed

    Heat related as well as backfiring sure does point back to an electrical issue even though you said the above list was all checked.

    Does the '77 Sporty have a condenser located at the ignition points area. The condenser is an important piece of the puzzle and without it, the secondary voltage will fall flat on it's face. It was not mentioned on your list.
  3. Jack Klarich

    Jack Klarich Guest

    Indeed it does have a condenser unless it has uni points then the condenser is built in to the points. I would recheck the rubbing block of the points and re gap and clean them, Replace the condenser just because:s Pull the advance mechanism out and look for wear on the roll pin, This is a common problem on Iron Head Sporsters and usually rears its ugly head when the engine is HOT
    Last edited by a moderator: Jul 22, 2011
  4. kdrok

    kdrok New Member

    Hey thanks for the reply. I did replace the condenser with the new points, and also eliminated the flyweights as a potential problem. I think i might try another new condenser just to rule it out, also going to bypass the kill switch, and wiring. Already did that with the key switch. I,m gonna get back to it and let you know what i find......if i find it!
  5. hobo55

    hobo55 Active Member

    I had a miss in my 79 fx that I chased for quit a while until I put the old condenser back in. New isn't always for sure.
  6. Slapp

    Slapp Junior Member

    Recheck condensor as well as voltage regulator, little black box. had one on my 78 sporty and the bike would run great then all of a sudden bike would die. Changed regulator no problem. For some reason I am thinking that I ended up using a voltage regulator from a dodge to fix the problem. Also check coil they used to heat up then fail.
    Here is a link to a wiring diagram.


    Good luck