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Discussion Starter · #1 ·
I'll lay it all down for you. It's a 1971 Honda cb350. last season the bike was running, firing on one cylinder and sporadically on the other. Due to my job I had to put the whole thing on hold till now. Went to start the bike and no spark to either spark plug. Checked the points and they were a mess so I replaced them. Still no spark.

With a volt meter I have checked to see where I am getting voltage throughout the bike. The battery is brand new and is getting voltage to through the system up to the kill switch and back down to the ignition coils/condensers. This is where things get tricky. With the bike powered on (just turning the key to on) I am getting 6 volts at the spark plug gap but no voltage at the points. I took the ignition coil units to a shop today and they tested them and said they were good. The starter motor works as well as the light system and horn. I seem to have continuity between all the wires from the points to the ignition coil unit.

I was told that I should not have any voltage at the spark plug gap unless the bike is firing. Please help! I dont know what else to check! :confused:
 

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I strongly suspect that you set the gap in the points when the timing mark was not lined up.Or-- It may be that the mark was lined up and you set the right side point gap when you should have been setting the left. Did you use a little test light to see exactly when the points came together?
 

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You will get voltage at the spark plug, because that part of the coil is connected to the primary winding; if you're using a digital voltmeter, it should be near battery voltage when the points are open.
 

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Sounds to me like you have the points gap too wide. You have voltage to the plug from the seccondary winding becuase the field is not collapsing... close th epoints a little
 

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Discussion Starter · #5 ·
Thanks so far. So the consensus seems to be the point aren't set right. I have the clymer manual but it isn't too clear on setting the points. How do I know which timing mark to set the right point to and which to set the left? I didn't use a test light to see when the points came together. Is there a way to make one from an old lamp or something?
 

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The rotor should have markings to distinguish them; most common is T and F vs. LT and LF, representing right and left, respectively.
 

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Timming marks

Now it was about 30 years agao when I owned my cb350 I was 14 at the time. I had to fix the transmission, rebuild and synch the carbs and tune it up so I had to get educated on it real fast since I thought I was real cool being the only kid driving himself to school in jr.high. With it being so long ago I do not remember the timming mark set up but then again you really don't need to, to set the points
The easiest way to set the points on a dual point system of any kind is to rotate the engine untill say the right point is all the way in the open position then adjust the left points.. then rotate the engine untill the left points are all the way open and adjust the right ones... Simple!
Remember the points aren't what times the engine they just open and close to first saturate the feild in the coil then collapse the circuit. if the mechanical part of the timming is set correctly as in cam to crank position then you are good to go. You fine tune the running timming by rotating the point plate while it is running
One thing to look out for is if I remember right theres not much room in there when you hook the primary wire and condenser to the points make sure the wire terminals are grounding against the case or advancement plate that the points are mounted on... hope this helps.. keep us updated.


:71baldboy:
 

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Discussion Starter · #8 ·
One more question. Should I be getting any power at the points on my voltmeter when they are either open or closed? Thanks so far.
 

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should be reading about 11.5v to the points... if I remember right when they are open...geez been a long time since I have had to mess with points... too many cob webs in this old brain I guess!
 

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Remember the points aren't what times the engine they just open and close to first saturate the feild in the coil then collapse the circuit. if the mechanical part of the timming is set correctly as in cam to crank position then you are good to go. You fine tune the running timming by rotating the point plate while it is running
:71baldboy:
The points are exactly what control the timing, which is when they open; with the gap set correctly when they are fully open, you would think that merely moving the plate they are attached to would adjust the timing for both, but it's not that simple. For one thing, the plate doesn't turn perfectly around the center, so the gap on one set can shift while getting the other to correct time. So, you can adjust the timing on one side, then tweak the gap on the other to get them both exactly on. Or, you can take that lack of centering to account, and carefully shift the plate next to one set to bring it back to correct time, if you can. But first, you have to know which set opens, relative to the marks on the rotor.
 

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Discussion Starter · #11 ·
Okay, so I think I have the points set. I set the alternator to the LF mark then set the left point to start its opening, then set the alternator to the R mark and set the right point. Is it possible that the condenser has gone bad. Witht the battery I get 6 volts at the spark plug gap. I have adjusted and readjusted the points. Im starting to think that maybe the condenser isnt doing its work?...Is there a way to test the condenser?
 

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With the power on, you should get battery voltage at the points; if it's less, the condenser may be leaking. One way to tell is unplug the condenser, and measure again.

The drop in voltage at the plug could just be due to the meter itself, since the spark winding is a fairly high resistance; the meter's current draw could be dropping the voltage.

Another test for the condenser is to measure the ohms; make sure you aren't touching both meter leads for this test. Initially, the ohms should be low, then rise as the condenser charges over a second or more, until it reads very high or open. Reversing the leads will cause the same jump to low ohms, but should end the same. If it reads open, or jumps to open really fast (fraction of a second), it is probably bad.
 

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With the power on, you should get battery voltage at the points; if it's less, the condenser may be leaking. One way to tell is unplug the condenser, and measure again.

The drop in voltage at the plug could just be due to the meter itself, since the spark winding is a fairly high resistance; the meter's current draw could be dropping the voltage.

Another test for the condenser is to measure the ohms; make sure you aren't touching both meter leads for this test. Initially, the ohms should be low, then rise as the condenser charges over a second or more, until it reads very high or open. Reversing the leads will cause the same jump to low ohms, but should end the same. If it reads open, or jumps to open really fast (fraction of a second), it is probably bad.
I am really confused as to where to touch the leads for the condenser test. When do you touch the leads to test the thing when it is "low"? Do you touch the leads and then turn the key on?
 

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If you're looking for voltage drop caused by the condensers, you make sure the points are open and measure the voltage across the points. If the condenser is leaking a lot, there will be a voltage drop across the coil; e.g., if the battery is 12.6V and the points are 12.2V, the condenser is leaking, and will reduce the spark strength.

If you're looking for an open or leaky condenser with the ohms test, you disconnect the condenser from the rest of the wiring so it's isolated, then read across the condenser leads (one may be the metal case). If it charges fast, it is mostly open inside, and not contributing to spark control. If it never reaches a really high (>100K) or open reading, it's starting to leak and isn't long for this world. When a capacitor charges, it goes quickly at first, then slows down, following a curve like a ball launched into the sky at an angle (but of course, not coming back down).
 

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Discussion Starter · #15 ·
So I picked up a much better multimeter, on that can test ohms, and have been trying it out. I do have about 12v at the spark plug. With the battery turned on I have 12v at the the three way connection between the point wire-condenser wire and wire going into the coil. No matter what I do I am not getting any voltage at the points themselves. I tried testing the condenser. I disconnected the wire from the rest of the circuit and put my tester lead on the wire and then on the metal condenser casing and did not get a reading.

Here's another thing I don't understand. When, at that three way conection between the piont wire-condenser wire-ignition coil wire, I disconnect only the condenser wire I still have no voltage at the points. It seems to me that since I have 12v coming down from the ignition coil wire and going through that three way connection, if all that is plugged in there is the ignition coil wire and the point wire I should be getting voltage at the points. I don't know if that makes any sense, but it's what I would think. (that is with the condenser wire disconnected). Any way, anything else you recommend, a new condenser or do you think its repair shop time? Thanks so much so far!
 

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Are you sure the points are open? During operation, the points close, shorting that connection to ground. When the points open, that connection will jump to about 300V, then briefly oscillate (create AC voltage) through the condenser as the spark jumps, causing the AC voltage to decay until the points close again.
 

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Discussion Starter · #17 ·
Okay okay...I figured it out. Here's the good news. I learned a lot this last week about how my bike works (as this is my first one) and feel very comfortable working on it. So I kept looking all over the web for people who have had the same issue and came across a forum with basically the same thing happening. All the replies were similar to what everyone said here, and then one reply said to check to make sure the point wires were connected to the points properly. He said that a common mistake is to connect the wire so it touches the part that bolts to the point plate. However, that turns it into a permanent ground. Well this is exactly what I had done. I changed the wire connection and put the little washers in the correct order and POOF spark! Lesson learned. Thanks for all the help, you guys are awesome. I just had a brain fart that lasted a week.
 
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