Hello everyone, I'm currently checking everything on my DT250 MX 1978, which I saved from being dismantled, because I have a kickback on the kickstarter and I'm not sure where it's coming from or whether it's normal.

When checking the ignition, I noticed that when I open the points, there is still a connection to ground. As far as I know, the multimeter should interrupt the connection as soon as I open the points. I don't know if that's the case with this ignition.

After reading a lot iam not sure if that behavior could be normal with the Yamaha ignition and the resistance only changes minimally.

If I separate the 3 cables on the capacitor so that the points is on its own, the test works.

At first I suspected the capacitor. But it insulates with infinite ohms against ground and has 260nF, which matches the specification.

I disconnected the excitation coil and measured it. But it also seems to be OK. Infinite ohms against the iron core and both wires to each other 3.3 ohms. 

I checked the ignition timing and TDC again and they fit perfectly.

thank you! 

Kickback isn't normal.  You need to check and probably set the timing.

The ("connected to ground") behavior you're describing is normal for an energy transfer magneto.  There is only a small change in resistance when points open.

That's the last year of the points ignition 250 so just wondering about your kick procedure. They're set at 3.2mm with no retard for starting like the "79 CDI model so do need a good follow through kick or it could bite back. Kick it against compression from the very very top meaning lever as vertical as it can be & against compression so you go through comp one & comp two before you run out of lever travel & it should leap into life as you exit comp two. Hope that sounds ok, I've never quite thought of it like that before but that's how it rolls. As Mark says check timing or even knock it back slightly. Also my big thing-- be sure that flywheel nut is Tight Tight or key gets damaged putting timing up the creek.

Ok maybe I was getting a bit carried away there & is it actually a runner?. If not & constant kickback but not run then go to the crank key as could be broken. If it runs as it is then probably not that.
Forgot to say welcome. Ringostar was one of my favourite Beatles & also the kids favourite as the Fat Controller in Thomas the Tank engine. Sorry not sure where I was heading with that. Enjoy your time here. Cheers from NZ down under.

Greetings from Tennessee 

Hi@all,

just some additionally informations:
- yes she runs, normally
- crank key is in good condition.
- checked TDC again and marked the TDC on Flywheel
- checked ignition time again and marked 3.2mm BTDC lefthanded the TDC-mark on the flywheel (flywheel rotates counterclockwise)
- the points are opening at exactly that timing point (ok they are at minimum and i should replace them but that should not trigger that behaviour)
- starting prozedure is like mentioned (I know that from my old 600cc 4-strokes). Searching for that compression point, get back the lever to maximum vertical and than kick it.
- Maybe iam now a bit gentle by kicking the lever strong and fully down because the that bite back. Got a decent kickback on the ankle last year.

- I also wondering on that DT 175 from my brother, there you can hit the lever nearly by hand and it will never kick back.
- So the 250MX is cool but i hate that (kicking back)-engine.
- The gearbox is even bad because i cannot switch the gears in high ref. It will fell into something like neutral-gear.(But thats another story) The kickback is the worst and that i can not accept.

- Well, just dont know how to proceed or what to check...

Best regards Steffen (from Germany)

Here you can see some pics about that stuff. 
The red point on case is my reference to check against the TDC and ignition. 

Pictures Ignition

Just be sure yu could mark 3.2 on flywheel & case then strobe it running to see how close it realy is. Sometimes strobing can tell a story.

yes i will do it again just to be sure... but last year I did exactly that first after getting the bike running ...I doesnt expect something changed.

A quick check in the lunch break: seperated the blue line from the points and did the resistance(continuity) check between the blue line and ground. Exacly at my 3.2mm mark the multimeter sounds.