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1979 Yamaha YZ250F_______Serial# 2X4007950
3.5 gallons gas to 12.8oz. Bel-Ray oil
Trans Oil- 10W30, drain- 750cc-850cc,rebuild- 800-900cc
Fork Oil- 10W20,SAE 15,SAE 10
Air Filter- 10W30
Gas- 90 or higher octane
Front Tire- 14 psi
Rear Tire- 4.10-18 psi, 4.50- 15 psi
Sparkplug- Champion N2G .018-.022 in. NGK B9ES, Hotter--> B8ES, B8EV
Chain Slack- 10-15m ?
Fork Air Pressure- 11.2 psi
Oil Capacity- 12.31oz. 364ml Distance from top with forks bottomed- 8.35in- 212mm
Gas:oil- 20:1 Yamalube R
Fuel Capacity- 2 gallons U.S.- Desert Tank- 3.75 gallons
Chain- DK 520 TR 107 links
Timing- .054 BTDC
Bore X Stroke- 70X64mm
Piston/Cylinder clearance- .0018-.0020"
Ring end gap- .012- .019"
Side clearance- Top- .0016-.003" 2nd- .0012-.0028"
Carburetor-Mikuni 38mm VM38ss 2x400
Main 400, Needle Jet-Q-O, Pilot-50, Needle 6F16, Clip position 4
Mixture screw- 1-1/2 turns out to highest RPM
Float Level- 0.71 inches, 18.1mm from gasket surface to float arm without gasket
Head nuts- 18ft.lb. Cylinder base nuts- 24ft.lb.
Clutch nut & primary gear- 54ft.lbs.
Drive sprocket- 54, Magneto rotor- 25
Clutch spring bolts- 6
Fork cap- 16.5, Front axle nut- 43
Front axle pinch bolt- 14, Handlebar bolts- 17
Fork bridge bolts- 16, Steering stem bolt- 68
Steering stem nut- 5 (adjust), Steering stem pinch bolt- 17, Fork cap bolt (allen)- 17
Rear axle nut- 58, Swingarm pivot nut- 58
Monoshock bolt to frame- 22, Adjust locknut- 43
Type 2 Magneto, resistance between primary terminal & mount- 0.6-1.0 ohm +/- 10%
Secondary resistance (sparkplug wire) 5.9 -6.2K ohms +/-20%