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  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    07 Jan 2019 09:12 AM
    Hi all, 
    Just recently bought myself an 86 XLH 1100 Sportster that I'm going to use as a base for a bobber build. 

    The bike itself is in great shape considering it's done 54k kms. However it's developed a misfire, which seems to only happen when the bike is warmed up. Runs and idles nicely when cold. It just coughs/splutters and loses all power after 10 mins of riding, but will idle fine once I get it back in the garage. It's just recently had a full service, including spark plugs and leads, and I replaced both the positive and negative battery cables (positive was frayed, so thought it might've been shorting) and cleaned off some grounds, but no change. 

    What could be causing this? Thanks in advance! 
    Jack 
  • Wideglider Posts: 479
    Illawarra NSW
    Stage 1 Poster Wideglider
    07 Jan 2019 10:06 AM
    Coil?
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    07 Jan 2019 11:28 AM
    Yeah I've just bought a twin tec single fire coil, spark plugs and leads this morning, will see if it fixes it tonight!
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    07 Jan 2019 08:27 PM
    Well that didn't change anything unfortunately..
  • Wideglider Posts: 479
    Illawarra NSW
    Stage 1 Poster Wideglider
    07 Jan 2019 10:36 PM
    Jack, well at least by replacing some parts you've eliminated some components. But you're gunna have to do some diagnostics, is it really electrical or could it be fuel/air? Are you getting full 12V at the coil primary? When the fault occurs, shut it down & see if your getting spark at both plugs. When its idling check for bad seal at intakes to both cylinders, could be sucking in excess air there. Is your fuel tank cap the vented type? It may be not venting causing fuel to be slow to fill carb float chamber. Try riding it with fuel cap loose.
  • tussuck Posts: 1640
    Melbourne
    Motor Head tussuck
    08 Jan 2019 09:46 AM
    What carb is on it?  Have you touched it?
    What Ignition module does it have as these things give up the ghost when the heat gets to them and this sounds heat related.

  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    08 Jan 2019 09:51 AM
    Factory carb, and it's got a twin tec vti ignition kit to replace the points. I replaced the inline fuel filter last night and was about to put it back together but wasn't sure if there was another filter in the pickup in the tank? Either way, didn't have the right sized spanner to check..will pick one up after work and check. 
  • tussuck Posts: 1640
    Melbourne
    Motor Head tussuck
    08 Jan 2019 07:17 PM
    Quoting 86Bobber on 08 Jan 2019 09:51 AM
    Factory carb, and it's got a twin tec vti ignition kit to replace the points. I replaced the inline fuel filter last night and was about to put it back together but wasn't sure if there was another filter in the pickup in the tank? Either way, didn't have the right sized spanner to check..will pick one up after work and check. 
    There should be one in the tank as well.
    If that does not pan out, then have you checked the battery voltages etc to make sure hat the alternator/regulator/battery are all good and charging etc
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    08 Jan 2019 07:25 PM
    Quoting 86Bobber on 08 Jan 2019 09:51 AM
    Factory carb, and it's got a twin tec vti ignition kit to replace the points. I replaced the inline fuel filter last night and was about to put it back together but wasn't sure if there was another filter in the pickup in the tank? Either way, didn't have the right sized spanner to check..will pick one up after work and check. 
    Quoting tussuck on 08 Jan 2019 07:17 PM
    There should be one in the tank as well.
    If that does not pan out, then have you checked the battery voltages etc to make sure hat the alternator/regulator/battery are all good and charging etc
    Alright new development. Replaced the fuel filter and cleaned out the in-tank strainer (it was filthy). Took it for a ride, no change, then the bike lost all electrical power but started back up 30 seconds later. Got it home and now with the ignition on, its switching on and turn off by itself, not the engine just the electrical system. So it's definitely something electrical..
  • Wideglider Posts: 479
    Illawarra NSW
    Stage 1 Poster Wideglider
    08 Jan 2019 07:59 PM
    Does your bike use fuses or circuit breakers? - Am guessing fuses? Either way, remove & make sure contacts are clean.
    Are battery terminals tight? 
  • brucefxdl Posts: 979
    south west victoria
    Performance Poster brucefxdl
    08 Jan 2019 09:17 PM
    Quoting 86Bobber on 08 Jan 2019 09:51 AM
    Factory carb, and it's got a twin tec vti ignition kit to replace the points. I replaced the inline fuel filter last night and was about to put it back together but wasn't sure if there was another filter in the pickup in the tank? Either way, didn't have the right sized spanner to check..will pick one up after work and check. 
    Quoting tussuck on 08 Jan 2019 07:17 PM
    There should be one in the tank as well.
    If that does not pan out, then have you checked the battery voltages etc to make sure hat the alternator/regulator/battery are all good and charging etc
    Quoting 86Bobber on 08 Jan 2019 07:25 PM
    Alright new development. Replaced the fuel filter and cleaned out the in-tank strainer (it was filthy). Took it for a ride, no change, then the bike lost all electrical power but started back up 30 seconds later. Got it home and now with the ignition on, its switching on and turn off by itself, not the engine just the electrical system. So it's definitely something electrical..
    not actually familiar with the electrics of this bike...but if it has an " on" relay in the key on circuit,that may a point to look at...along with fuses,connections ect as suggested
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    08 Jan 2019 09:37 PM
    Quoting Wideglider on 08 Jan 2019 07:59 PMedited: 08 Jan 2019 08:01 PM
    Does your bike use fuses or circuit breakers? - Am guessing fuses? Either way, remove & make sure contacts are clean.
    Are battery terminals tight? 
    It has circuit breakers and one more modern relay, which I assume isnt factory as it's Bosch. 
  • Wideglider Posts: 479
    Illawarra NSW
    Stage 1 Poster Wideglider
    08 Jan 2019 09:43 PM
    Quoting Wideglider on 08 Jan 2019 07:59 PMedited: 08 Jan 2019 08:01 PM
    Does your bike use fuses or circuit breakers? - Am guessing fuses? Either way, remove & make sure contacts are clean.
    Are battery terminals tight? 
    Quoting 86Bobber on 08 Jan 2019 09:37 PM
    It has circuit breakers and one more modern relay, which I assume isnt factory as it's Bosch. 
    The circuit breakers will auto reset, this could be what is happening. Maybe then something is drawing too much current or shorting occasionally to cause this, or circuit breaker faulty.
    Suggest you buy/download a workshop manual, it will have the wiring diagram. To identify the fault, you may have to temporarily bypass sections of the circuit to observe.
    But of course the issue may be something completely different. Do you have a multi-meter? If not get one, you have to diagnose - otherwise we are just all taking stabs in the dark.
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    09 Jan 2019 12:50 AM
    Just discovered a couple of loose ground wires up by the head light assembly! Will take it for a quick ride before work tomorrow and see how she goes! 
  • Krash Kinkade Posts: 2404
    Motor Head Krash Kinkade
    09 Jan 2019 10:26 AM
    Quoting 86Bobber on 09 Jan 2019 12:50 AM
    Just discovered a couple of loose ground wires up by the head light assembly! Will take it for a quick ride before work tomorrow and see how she goes! 
    need to go right through the wiring by sound of it, over the years I've had things like that happen, I changed the wiring on my old kick start only shovel from circuit breaker to a fuse, I used to carry spare fuses. was blowing fuses when I turned on lights. ( with out lights was ok ) . went through wiring found one flat wire, replaced it and no more problem. can be hard to find the wire sometimes!! good luck 
  • 86Bobber Posts: 8
    Stock Poster 86Bobber
    19 Jan 2019 07:11 PM
    So I'm fairly sure after replacing my coil, leads, spark plugs, battery, fuel filter, cleaning my fuel tank, testing my regulator and stator and compression testing to make sure my valves weren't damaged...it was the main circuit breaker after all. Just took it out for a decent 45 minute ride and had no issues at all. Will report back if the misfire rears its head again, but it looks like I'm in the clear for now! Thanks for the help everyone.
  • Wideglider Posts: 479
    Illawarra NSW
    Stage 1 Poster Wideglider
    19 Jan 2019 08:42 PM
    Quoting 86Bobber on 19 Jan 2019 07:11 PM
    So I'm fairly sure after replacing my coil, leads, spark plugs, battery, fuel filter, cleaning my fuel tank, testing my regulator and stator and compression testing to make sure my valves weren't damaged...it was the main circuit breaker after all. Just took it out for a decent 45 minute ride and had no issues at all. Will report back if the misfire rears its head again, but it looks like I'm in the clear for now! Thanks for the help everyone.
    Glad you got it sorted, you even have piece of mind with many new parts (though it cost you a shitload). Thanks for getting back to us - not everyone does that.
    A workshop manual with wiring diagram along with a diagnostic approach is the best investment you can make, will save you the heartache & hundreds of dollars.

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