Yamaha 250 dirt bike query

Two workers bought an old dirt bike from another coworker. Right now it won't fire and they keep asking me for advice. I don't really know 2 strokes. What kind of ignition system do these things have?

Need more info.. but being 2 stroke there isn't much to them

Pull the plug and see it sparks during kick

Make sure the fuel mix is PERFECT (clean the carb too)

First check for spark. Then for gas. If You have both and no air leak and it won't start, then it would be timing, but I don't think that it is adjustabe on modern dirtbikes.

What year is the bike? Yamaha has been building 250s for 40 or 50 years now...old ones used a magneto, I'm not sure about newer ones.

He thinks its a mid 70s model. The quintessential two stroke air cooled enduro. One owner said when he sued to ride it years ago it needed a new plug pretty often. The auto oiler was disconnected by the DPO and they premixed the gas a little "rich". The guy who has it now says it seems to have spark sometimes, but not on other tries. WHo knows. Neither of these guys knows much about machinery. THey are civil engineers.

Clean and set the points.

Simple magneto ignition setup. Beware the kill switches, particularly a kickstand killswitch. Yamaha loves kickstand kill switches, and they frequently cause loss of spark.

Do you have points with a magneto system?

Yes

Well I have learned something today.

CDI's have no points just coils and a pick up with a 2x3x1.5 box normaly on yamaha of 70's age CDI box is on the rear fenderjust above the gear box in a 3 leg rubber holder and has two triangle plugs or is it 1 triangle and one 2 wire...brain fart. 74 and up MX bikes had CDI enduro's held out a few years more. If it has points you should be able to pull the left side cover look over the cover if you have an oilly film chances are the crank bearings are toast and the seal is not able to hold in the mixture. Remember 2 stroke crank sael see both neg and pos presure.