I'm rebuilding the engine on my 1975 dt125. This nay be a silly question but what size bolt/puller do you need to remove the rotor/flywheel thing on the giant magneto systems on the dt125s. My service manual doesn't show how to do that.

I'm thinking you have the electric start model so puller is a 10x1.25 thread with an extended nose.
`10x1.25 pitch.
Nose bit is 31mm long & 5.5mm diameter. 10mm bit is 87mm long. I think the nose bit bottoms out in the hole so the 100mm bit doesn't contact the end of the taper. I think a 10mm 1.25 pitch good tensile strength bolt would still do the job ok pushing on the end of the shaft if you were stuck but i'd taper the first few threads a little to avoid a problem when you smack the bolt after tightening as might try & swell the end of the bolt then be difficult to wind out without a fight.

Several other sources and options discussed here:
www.yamaha-enduros.com/index.php/forums/...te=all&childforums=1

Try this post... same puller.

yamaha-enduros.com/index.php/forums/rest...store?start=20#99440

Also, technically the US DT125 has a "generator/starter" or sometimes called "dynamo/starter" system.

A "magneto" is a fixed output alternator system that has permanent magnets and does not require a battery to run.

Your generator system needs a battery to work.

Just mentioning this because there's a big difference in the systems... most Enduros have a magneto. The generator used on the 125's is the exception.