I don't think they made DT400s in '86.
And it's not listed in the OEM parts catalog:
If it's a DT400, then it's a great bike for exploring. Two stroke so it's a little touchy, but for 400 bucks if it runs, it's worth it. The AHRMA guys buy them for that price a lot of times even if they don't run.
If it's an '86, then it's something else.
Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker