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1976 DT400 ignition issue

  • ldw72120
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1976 DT400 ignition issue was created by ldw72120

I have a DT360 and am familiar with the ignition issues with this model.  After a lot of frustration, I ended up installing a Vape ignition.
I am considering purchasing a 1976 DT400 that the owner says has no spark.  I know there can be many causes for this and some are easy fixes.  I have searched the forums for issues on the DT400 and noted some of the same ignition issues as the DT360.  Are the CDI issues as common on the DT400 as they are on DT360? I am trying to make up my mind if the DT400 is a good deal if I have to purchase Vape ignition.
Your thoughts please. 
16 Oct 2025 08:01 #1

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Replied by MarkT on topic 1976 DT400 ignition issue

I'd say yes, problematic.  The monoshock 400 (1977) was where they changed the CDI design and those seem a little more reliable than the 74-76 CDI's.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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16 Oct 2025 09:28 #2

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Replied by pabdt on topic 1976 DT400 ignition issue

50 year old parts like a CDI always concern me. I don't want to get way out in the forest, you know bears, mountain lions, wild HUMANS, and break down. Looking at a 77 DT250 on Monday myself.
________________________________________________
1969 Yamaha CT1 175
1974 Yamaha DT125A
1974 Yamaha DT360A with SP96 Exhaust
Next…196x-197x Yamaha something.
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17 Oct 2025 21:03 #3

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Replied by Jake2020 on topic 1976 DT400 ignition issue

Just finished putting my 76 DT 400 back together, but I have not spark. What are the list of things to start with. I may swap Coil today and see if that makes any difference and disconnect the KILL Switch too., but then I am not sure what to do next
25 Oct 2025 08:26 #4

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Replied by pabdt on topic 1976 DT400 ignition issue

I just fixed a 250 that had a shorted primary coil.  That’s as good as a kill switch.  
________________________________________________
1969 Yamaha CT1 175
1974 Yamaha DT125A
1974 Yamaha DT360A with SP96 Exhaust
Next…196x-197x Yamaha something.
25 Oct 2025 08:39 #5

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  • pahiker
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Replied by pahiker on topic 1976 DT400 ignition issue

What is the history, did it have spark before? I'd go for the simple stuff first, recheck connections and try a known good spark plug.
1973 Yamaha RT3
2023 Triumph Tiger 1200 GT Pro
2024 Suzuki DR650
The following user(s) Liked this Post: MarkT, Schu, Ht1kid
25 Oct 2025 10:42 #6

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