« previous next »
Pages: [1]   Go Down

Author Topic: Point set for 1-4 are sparking 78 750F  (Read 523 times)

0 Members and 2 Guests are viewing this topic.

Offline SS350Sport

  • Full Member
  • *
  • Posts: 12
Point set for 1-4 are sparking 78 750F
« on: June 07, 2017, 05:46:54 pm »
I just purchased a low mileage (5K) 78 Super Sport motor and I am attempting a first start. Everything checks out good except for the points for the 1-4 coil are sparking and the 1-4 plugs are not firing. I have a 77K that likes to eat condensers so I figured this was an easy fix. Not true. I swapped the condenser from the 2-3 side and the 1-4 points still throw spark. I changed the 1-4 point set and it still sparks. I can swap the yellow/blue wire terminals near the rear brake switch and I can get the 1-4 plugs to fire. Any ideas?
Logged
74 CB 750K
76 CB 750F
77 CB 750K
78 CB 750K
79 CBX

Offline Glenn Stauffer

  • SOHC/4 #3 - Member since 1994
  • Administrator
  • Expert
  • *****
  • Posts: 1,295
    • The SOHC/4 Owners Group
Re: Point set for 1-4 are sparking 78 750F
« Reply #1 on: June 16, 2017, 04:15:45 am »
bumping this one up - apologies for the delayed posting; it was hung-up in the moderation queue
Logged

Offline lrutt

  • Expert
  • ****
  • Posts: 916
Re: Point set for 1-4 are sparking 78 750F
« Reply #2 on: June 16, 2017, 10:19:41 am »
Sounds like questionable coil to me.
Logged
06 Harley Sporster 1200C, 06 Triumph Scrambler, 01 Ducati Chromo 900, 01 Honda XR650L, 94 Harley Heritage, 88 Honda Hawk GT, 84 Yamaha Virago 1000, 78 Honda 750K w/sidecar, 77 Moto Guzzi Lemans 850, 76 Honda CB750K, 73 Norton 850, 73 Honda Z50, 70 & 65 Honda Trail 90, 70 & 71 Triumph 650s, 65 Honda 305 Dream, 81 Honda 70 Passport, 70 Suzuki T250II, 71 Yamaha 360 RT1B, 77 BMW R75/7, 75 Honda CB550K, 70 Honda CT70

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Point set for 1-4 are sparking 78 750F
« Reply #3 on: June 16, 2017, 10:58:16 am »
Measure the resistance of the coil primary and compare to the coil that is firing.

Remove/unscrew the plug caps from the HT wires and measure the resistance of the coil secondary.  Compare to the 2-3 Coil.

report results.
Logged
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline Dracon

  • Wannabe Old Timer...
  • Enthusiast
  • **
  • Posts: 100
Re: Point set for 1-4 are sparking 78 750F
« Reply #4 on: June 16, 2017, 11:11:50 am »
If swapping the blue and yellow wires gets spark to 1 and 4 then the wire from the points to the connector has been severed or corroded somehow.  Try swapping those wires from the other bike and I bet it works.
Logged
Pages: [1]   Go Up
« previous next »