1969 Honda CB 350 - No Spark Trouble

Discussion in 'Old's Cool' started by Bobbykrussell, Jun 19, 2017.

  1. Bobbykrussell

    Bobbykrussell Adventurer

    Jun 27, 2013
    Hey there

    I have a 1969 Honda CB 350 that was running perfectly but decided to stop firing up.
    Looking for a few more ideas as I have exhausted my troubleshooting checklist and want to make sure I take the next methodical and logical step to troubleshoot further.

    The first thing I noticed is it has no spark on the right hand side of the bike so here is what I have done to start troubleshooting:

    1. New battery - I went ahead and bought a new one since I know these old CB's hate weak // old batteries. No dice.

    2. Pulled plugs - replaced with new plugs no dice. Checked spark.
    Right side = no spark.
    Left side = strong spark.

    3. Check Points - Removed cover ( I know these can ground out often and cause issues, no dice there either.) I can however see spark on the corresponding left side points = strong spark, but No spark on my points for the right side.

    With this diagnosis so far, my thinking is that the points need to be replaced orrr the timing somehow got so out of whack that it needs to be re-timed.

    Is this a correct and fair assumption? My gut tells me it's the points as this was a running motorcycle, that sat indoors in a climate controlled store for just 4 months with no gas.

    Am I going down the right path or overlooking something?
  2. snarlyjohn

    snarlyjohn Dunning-Kruger poster boy

    Apr 1, 2016
    Each coil should have two primary connections: one should have power when the ignition is switched on and the other will be connected to the points. The first test should be to check (with a test light or multimeter) whether the + terminal is actually getting power with the key switched on.

    If it passes that test then you should test the coil itself. Remove the plug but leave it connected and grounded so you can see if it sparks. Disconnect the wire from the coil that runs to the points and in its place connect a length of wire a foot or so long. Turn on the ignition and quickly tap-tap-tap the other end of that wire on the cylinder head or some other good ground. Every time you tap the wire you should get a spark from the plug. If you don't then that indicates that the coil is faulty.

    If it sparks with the temporary test wire then that indicates the problem is with either the points, the condensor or the wiring from coil to points.
  3. Generalmisconception

    Generalmisconception Generalmisconception

    May 22, 2012
    Ogden Utah
    I think your assumption is a good one, but I'd also suggest using some light sand paper on the offending points before getting too much further along.
  4. 83XLX

    83XLX Been here awhile

    Oct 12, 2009
    Heart of Dixie
    First, make sure that set of points is actually opening and closing cleanly. Then, check the connections in the big rectangular multi-wire connector under the seat.
  5. gravityisnotmyfriend

    gravityisnotmyfriend Long timer

    Jun 1, 2012
    ((kg*m)/s^2), IA, USA

    I use emery cloth - but light sand paper would work. There's a good chance you just have corrosion on the point contacts.
  6. pikl

    pikl Adventurer

    Mar 15, 2015
    I'd clean the points. If you see sparks on the points, maybe the condensers are bad. They may be the original 47 year old ones...
    If you see a spark on one spark plug, try replacing the wires from the points, and see if the other coil throws a spark as well. If it does, something is wrong with the other points or condenser.
    If the coils are original, maybe you could also consider replacing them. I think you cannot replace the spark plug cables in the original coils, and with time, the cables get bad and cause all sorts of problems, especially when wet. Yamaha XS650 coils are cheap, the cables are replaceable and will work good. I got a pair for my CB360 for some 30€, and managed to get them neatly mounted in the original space with a custom bracket.
    Also, check all the connections, it may be as simple as that...
  7. baloneyskin daddy

    baloneyskin daddy bikaholic

    Oct 21, 2009
    southcentral PA.
    You guys always make things hard. Simply switch the wires from the left coil to the right and vice versa. If the coil that had no spark now worksand the other doesn't the problem is either points or condenser. If the coil still has no spark but the other one still works its the coil.Unless theres a break in the wiring or a bad connection somewhere.
    pikl likes this.
  8. 1150Pappy

    1150Pappy Been here awhile

    Jan 16, 2014
    Central Florida
    Will join in the oxidized points group. I use 400 grit or 600 grit (better) to clean the points. You do not want a rough surface on them as it will decrease the overall life of the points set.
  9. Boomer343

    Boomer343 Been here awhile

    Apr 14, 2014
    The resistor caps should be taken off the plug wires and the wires cut back slightly then the caps installed. They simply screw on and off. They are cheap so might just want to replace them. You should have non resistor plugs to go with the resistor caps.

    Some points have been an issue with shorting out and quality ones are hard to find. I usually find a lot of electrical connections that have corroded or become loose so would advise checking all of them.

    You might want to head over to the Honda Twins board for more info.

    With a bit of luck I'll be firing up one of my cb350's tomorrow. A hipster dufus spent money on paint but didn't do the engine seals and one blew out, dumped all the oil and baked the top end..... got the cam so hot it melted the insulation on the points wire connections.