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TOPIC: Ignition Timing Weirdness..

Ignition Timing Weirdness.. 15 Apr 2019 08:30 #1

  • Kayto
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So I've been bringing a '74 DT250 A back from barn abandonment. The odometer reads 101.5 miles, and all wear components (OEM tires, brakes, piston, internals, swingarm pivot, etc) all indicate that this mileage is correct. Set the ignition timing this weekend. The points are OEM. Screws and stuff indicate that they were never messed with from factory. Set up the dial indicator to read the piston rise, and set the point opening to 3.2 mm / .13" BTDC. Found that it was very advanced. Tried adjusting the point opening, but there was not enough adjustment range to do so. Loosened the base plate behind the flywheel and moved it clockwise the entire way. Helped, but not enough. Ended up expanding the slots slightly, allowing the base plate to rotate clockwise a bit more, and was then able to finally get the points to open at the specified setting. Ohm meter and dial indicator aren't lying to me, but the factory "tang" and flywheel hash-mark are not longer anywhere close to each other. Points are not worn at all. Flywheel key is in place and "square". Any ideas as to
why I had to move the plate so much to get things to read right?? Thanks!

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Ignition Timing Weirdness.. 15 Apr 2019 10:35 #2

  • MarkT
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First thought is flywheel key... you said it's in place and good..

The thing that doesn't make sense in your description is you said the timing was too advanced... but then you rotated the stator plate clockwise? Rotating the stator plate clockwise advances the timing even more.

The mistake I've made is getting the piston to TDC and then rotating the flywheel counterclockwise (normal direction of rotation) instead of clockwise, (opposite of normal engine rotation) until the piston drops 3.2mm.

if you can take a picture of where you have the stator plate, that will help.

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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

Ignition Timing Weirdness.. 15 Apr 2019 16:28 #3

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I meant to say that I rotated the plate >counter-clockwise<. Screwed up the description. My bad. I just cannot figure out why I had to go to such extremes to get it set. When I first took it apart (put in fresh crank seals for good measure), the I marked the plate and screw location It was pretty much set at the center of the slots. Started off trying to time it based on the original positioning. It was really, really BTDC. For what it's worth, engine has not damage. Exterior cases are unscathed, crank spins quietly, like new, etc. Happy to set up the dial indicator and break out the flywheel puller again if someone has an idea. Thanks!

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Ignition Timing Weirdness.. 15 Apr 2019 16:58 #4

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If you rotated the stator plate counterclockwise I'm pretty sure you are trying to set the timing after top dead center (ATDC), not before top dead center (BTDC).

Easy to mix up... I've done it. After you get the piston at TDC, make sure you rotate the flywheel clockwise to find 3.15mm BTDC.
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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

Ignition Timing Weirdness.. 16 Apr 2019 17:42 #5

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Mark T and anyone else who gave this a think.... First thanks for the kind words. You were indeed right. Looks like a scrambled it up and ended up fighting myself against ATDC. Tonight, I simply started over. Put the stator plate back where it started (pretty much centered in what was the OEM slot). From there, set the piston to 3.2 mm/.13" BTDC. Then, I very gently moved the point gap until my OHM meter danced, indicating point opening. Took a dozen or so adjustments until I got it aligned nicely with the dial-guage, but it's there now. I think that I first did this when I was tired and in the wrong mood, not good. Fresh look (and encouragement from this site) made the difference. THANKS!
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Ignition Timing Weirdness.. 16 Apr 2019 19:30 #6

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Congratulations!!! :likey

Glad you got it figured out! :Buds

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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

Ignition Timing Weirdness.. 17 Apr 2019 07:57 #7

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Glad you figured it out, MarkT is always a big help.

I saw the photo of your DT250, your right it sure looks like someone crashed it soon after buying and tossed it in the barn until you found it.

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Thanks Mark
Roseville, Ca.

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