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TOPIC: Crank Woodruff Key size on a '72 DT250??

Crank Woodruff Key size on a '72 DT250?? 12 May 2019 17:02 #1

  • colloquialoatmeal
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Good afternoon from Portland Oregon!

Got a '72 DT250 and in the process of getting it going. Has strong compression but no spark so I ordered a new battery, condenser, ignition coil and plug. Replaced everything but noticed when I took the flywheel off that the woodruff key is broken off on the crank.

Does anyone happen to know the size of this key?

Thanks!

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Crank Woodruff Key size on a '72 DT250?? 12 May 2019 21:14 #2

  • MarkT
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Getting one from Yamaha is your best bet... too many reports of generic keys shearing.

Also make sure taper is a good fit, clean, and oil free and flywheel is torqued properly. Key is flea power and mostly an assembly aid... if taper isn't a good fit new key will shear immediately.

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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

Crank Woodruff Key size on a '72 DT250?? 13 May 2019 05:27 #3

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P.S. If it's a 1972, technically it's a DT2. "DT250" wasn't a model until 1974 and later. Not a big deal, just good to know if looking for parts, etc.

Checking your VIN against the VIN tables in the Tech Library is always a good idea... many bikes are registered and titled as different years and models than they actually are. Yamaha also used confusing VIN numbers like using "DT1F" as the VIN number prefix for several years just preceding the major redesign for 1974. A bike with a "DT1F" prefix could be the first generation piston port "5 port" engine design or the 72-73 reed valve "7 port" design.
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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

Crank Woodruff Key size on a '72 DT250?? 16 May 2019 23:16 #4

  • colloquialoatmeal
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Thanks!

I managed to find a correctly sized woodruff key from my local hardware store; it fit in with no issue and the flywheel runs on it perfectly. I've kicked it a few times and it hasn't sheared.

I was hoping the broken woodruff key was the cause of my lost spark but after changing the key and the condenser, I am still without spark. I've noticed that there isn't a DT2 manual in the tech library; any chance you know of one around the interwebs?

Or even just a wiring diagram so I can get this thing to fart to life.

Thanks for the help!

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Crank Woodruff Key size on a '72 DT250?? 17 May 2019 06:41 #5

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It's one wire from stator to coil. Wiring diagrams and manuals available in the Tech Library. Here's a link to one of the service manuals.

yamaha-enduros.com/index.php/workshop/se...360cc-service-manual
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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

Crank Woodruff Key size on a '72 DT250?? 17 May 2019 10:03 #6

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Huh. I'm not sure why I didn't see that manual, but thanks for posting it!!

Another question if I might: if I jump the stator wire to the ignition coil to check for spark, will the ignition need to be in the on position? I'm thinking I may not have the ignition sorted out as there is a brown wire and green-yellow wire coming from the headlight that is bare. When I turn the key, with a fresh battery, I'm not getting lights or anything.

I'll follow up with the wiring diagram and hopefully I can get this thing going. Thanks for all the help so far!

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Crank Woodruff Key size on a '72 DT250?? 17 May 2019 10:11 #7

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Single black wire (sometimes black with white stripe) from points/condenser on stator to ignition coil is all you need for spark. No battery. No other connections.

Key switch grounds this wire to kill spark.

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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
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