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Thread pitch on generator side of crank of CR250

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I'm turning up a flywheel weight for a 01 CR250, I need to cut an internal thread in the weight to screw it on to the crank . Looking at the crank threads they look like M12 fine(12mm),however,a M12 fine nut won't screw on,neither will a standard M12 nut, what thread is this? Thanks.

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Thanks to mark5pto I've just spent $20 on a 12mm x 1.25 tap that is NOT the same thread as the crank,if you don't know the answer to my question don't just guess!

So the thread must either be M12 x 1, or M12 x 1.5, it doesn't look fine enough for the first so it should be the latter.

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maybe you could measure the threads. 1, 1.25, 1.5 just means the distance of each thread in mm. or take the nut to a hardware store and see what bolt it threads onto lol

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I didnt "guess" at the thread pitch. I measured my old generator nut, which has the same part # as your bike, and came up with the 1.25. I will remeasure tomorrow (as my tap/die set is at work) .........

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KTM, yeah I know what the 1.0,1.25,1.5 stands for ,there isn't a nut and bolt store within 10 miles of me,and very doubtful if they would stock metric fine.

Mtrehy, most of the stuff I work on is UNC or UNF(and I don't need to measure those,I can eyeball them), I only use the stock metric stuff for bolting together 'general' items. 99% of my taps and dies are Imperial.

Mark5pt0, I will be interested on what your remeasure is,I tried to run the new M12 X 1.25 taps I bought through the generator nut but it is VERY tight,and I can feel it cutting the thread. It did appear to be a match for the thread on the end of the crank though,so, I tapped the flywheel weight, but it will only 'just' start to screw on to the crank and then it locks up. I have cut the threads perfectly and both the crank threads and flywheel weight threads are clean. I don't want to force it and ruin the crank.

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Hey Armcosurfer,

I measured the generator nut again, trying a 1.0, 1.25 and 1.5 pitch. Its definately a 1.25 pitch. I even put it under a lighted magnifier for a close, precise look at the mating of the tool vs. the threads. I cant answer why your flywheel wont thread onto the crank smoothly....wish I knew why......Hope you get it solved.

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