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02 Sep 2019
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TOPIC: 1971 Yamaha CT1-C Ignition Issues

1971 Yamaha CT1-C Ignition Issues 10 Jul 2019 20:23 #1

  • ajacstern23
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Hello,

I recently got a 1971 Yamaha ct1 off of craigslist that needs restoration. The first issue I'm working on is that it has no spark. Unfortunately, the previous owner stripped almost every screw including the ones holding the stator on, and I can't angle grind them out due them being recessed.

I am trying to work on it with the stator still on. The little solder bridge you see on the bottom of the source coil isn't touching the condenser housing. It was on there originally but looked "aftermarket" so I tried cutting it to see if that was the problem. The key works fine but I hotwired it just in case. I have replaced the source coil, condenser, and points but still no spark (don't know if these parts are good or not, but they look and test fine as far as I can tell). I was using the 3vdc power source spark checker method and was getting spark from that, but after I changed out the source coil, condenser, and points I can no longer get spark from the 3vdc method. I have tried two different new spark plugs. I have checked the ignition coil and everything seems fine. 4.5kohm on the spark plug lead and 9.5kohm on the primary coil.

Any ideas would be greatly appreciated, thanks!
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1971 Yamaha CT1-C Ignition Issues 10 Jul 2019 22:57 #2

  • RT325
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Ok i'll probably confuse the issue but the source coil is the one on the right--the smaller coil. CT2 book says on the plug coil, 1.6 primary & 6.6K thousand secondary, That's hooking it via the primary of course. That'd be minus the plug cap or just about double it i'd guess. CT3 which would be ball park the same says 2.1ohms via the black wire. If you had the coil disconnected from points & condenser--new coil. If you put a bit of cardboard in the points--i think that'd do it--or does condenser still play a part, anyway coil in ya hand type thing, source coil that is. What was going on with the solder trick?, was someone trying to get a good earth for condenser or was the condenser mount broken. Hope you sort it. Spark, or lack of, can be so damn frustrating.
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1971 Yamaha CT1-C Ignition Issues 11 Jul 2019 12:15 #3

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Hmm I didn't consider that I might be confusing the charging coil and source coil, but that is a possibility. However, the replacement coil+points+condenser set I got had the left coil soldered to the positive of the condenser, so that should be the source coil? Partzilla does list it as the lighting coil, but I thought it was the source coil that connected to the condenser. Also when I kick start it I can see the dash lights come on a little. I'm not really sure what the solder bridge was about as it was grounding out the positive side of the condenser so it didn't make any sense to me. I'll check the resistances of the coils again when I get home. I was initially unsure whether it was the correct stator because it looks slightly different from the service manual but from all the pictures I can find online it looks right. I might try replacing the ignition coil but it was working fine just yesterday and it still tests with the same resistance, but for some reason it's not working now. Thanks for the advice!

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1971 Yamaha CT1-C Ignition Issues 11 Jul 2019 18:33 #4

  • Capt.Dave
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Drill the screw heads out, they all strip.
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1971 Yamaha CT1-C Ignition Issues 11 Jul 2019 20:00 #5

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Good to know, I considered it but was worried that the head would snap off. Even if I got the stator off I don't know what is broken. I've replaced all the components on the stator. Only thing I haven't replaced is the wiring harness and ignition coil but the ignition coil tests relatively fine (9.5kohm and 5.7ohm, factory is supposed to be 11kohm and 4.9 so they seem close enough) and the wiring harness checks out ok. It's tough because everything seems like it's working but evidently it's not. Maybe some of the replacement components I got for the stator aren't good, I'm the most suspect about the condenser but not entirely sure how to check it.

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1971 Yamaha CT1-C Ignition Issues 12 Jul 2019 00:29 #6

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your coil primary should be 4.9 ohms, 9.5kohms shows coil is bad, did you test w/wire to points disconnected? It needs to be. Look in service manual!

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1971 Yamaha CT1-C Ignition Issues 12 Jul 2019 00:38 #7

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The left looks to me to be the source coil (they have smaller wire) source coil, condenser, points and wire to ignition coil all soldered on condenser

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1971 Yamaha CT1-C Ignition Issues 12 Jul 2019 14:16 #8

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The primary ignition coil is 5.4ohm it is the secondary coil that is 9.5kohm. They are pretty close to factory spec, not perfect though. I can get a spark from the ignition coil using 3 d batteries (4.5volts) but I can't get a spark from 2 d volt batteries (3volts). That shouldn't be a problem because the source coil produces like 6v, correct? Thanks for the confirmation on the source coil.

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1971 Yamaha CT1-C Ignition Issues 16 Jul 2019 11:34 #9

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Well I replaced the wiring harness and still got no luck. Left it for a couple days and when I came back it decided to spark. I think the points weren't opening but no idea why it is working now. However, spark doesn't only come out of the spark plug, it also comes out of the flywheel. Is this ok? It doesn't seem normal but if it works it works I guess. Going to do timing now, any tips? I am using a harbor freight dial gauge. Also, can I reuse the metal headgasket? I plan to replace the gaskets at some point but for now I'd like to see if it has enough compression to run. Thanks!

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1971 Yamaha CT1-C Ignition Issues 16 Jul 2019 16:03 #10

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If you can see spark at the flywheel & you mean points sparking wildly it sounds like condenser has failed or failed to be connected. You'd see sparking at the points with it running in the dark but not like an arc welder so if you have 'that' then somethings very wrong. In fact if it's like that then it'll never run as the spark at the plug will have no guts to it to fire under compression. Hope i'm wrong--we want to hear it run!!.
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