bike won't start

[PDS00]

Bought a 87 250r used. It wouldn't start when I bought it but he asured me it ran (mistake: don't ever buy on the premise of some guy that said it ran before). Anyway I worked on the carb and replace the plug to a b8egv. It fired right up afterward. 2 weeks go by and when I tried to start it last night it wouldn't fire. It acts like it did with the old plug in it. Could i have fouled a brand new plug in a matter of 5min of run time? I'm gonna replace the plug in the morning and if that doesn't work i'm gonna check the flywheel. It just stumps me that it ran for 5min on a new plug and sits for 2 weeks and now won't fire. This bike has become a million dollar machine.

[DWR270]

How long did it sit before you bought it?
All stock? And what type of gas and oil and ratio? Did it smoke a lot when you first started it?

[PDS00]

got it going today. turns out i had some junk in the carb so i cleaned it out again and it fired right up. found out it's jetted to 80 degrees + so i'll have to rejet.

[f150dan]

Rich carb jets or fat oil mixture can foul plugs quick.

[quadtech92]

just make sure you are for sure running a 32:1 ratio which is about 4oz to a gallon and read up on the jetting according to the manual and you will be all set mine sat for 20+ yrs and i hsd it running in a couple days and still going strong