THE STOCK SIZE OF CHAIN AND SPROCKET'S ON THE 73 THRU 81 ATC70 IS 72 LINKS OF CHAIN 14T FRONT SPK AND 35T REAR SPK. ON THE 82 THRU 85 ATC AND ALL TRX70'S THE CHAIN IS 72LINKS THE FRONT SPK IS 13T AND THE REAR IS 36TOOTH. ALL THE OPTIONAL SIZES WILL FIT ANY ATC OR TRX AS FAR AS THE SPROCKETS GO, BUT THE CHAIN MUST BE CUT TO THE CORRECT LENGTH.ONE SPECIAL NOTE** IF YOU CHOOSE THIS 12 TOOTH FRONT SPROCKET IT WILL REQUIRE THE (79K) LOCK PLATE, INSTEAD OF THE STOCK LOCKING PLATE. C&SFRONT_SPROCKET_SIZE: 12TOOTH___24J13TOOTH___17A14TOOTH___16i15TOOTH___14C REAR_SPROCKET_SIZE: 35TOOTH___(14D)36T____(17A)38T____(16J) CHAIN_LENGTHS: 72_LINKS76_LINKS86_LINKS @ *LOCK PLATE FR SPK Z50R'S_82_TO_87 ATC70_82_-_85 TRX70_ALL 23802-041-010 1/21A (R2202)FOR USE WITH THE 12 TOOTH CT70 SPROCKET !!!! R2202 @ *LOCK_PLATE FR._SPK. (CT70_69_94) (ATC70_74_81) (Z50R_88_99) (ALL_C70'S) (ALL_PASSPORTS) 1/20A (R2026) THIS PLATE KEEPS YOUR "STOCK" FRONT SPROCKET FROM FALLING OFF OF THE CT70K0 THRU 94 ,, ATC70'S 74 THRU 1981,, Z50R'S 1988 TO 1999 AND THE XR70'S THRU 1999. R2026 @ *BOLT_FRONT SPROCKET LOCKING_PLATE (6x8 MM) FITS ALL BUT (Z50 81 AND OLDER) 92101-06008-0A 1/22A (53D)THIS BOLT WORKS WITH OUR #24K AND #79K LOCKING PLATES. SOLD EACH, OEM HONDA BOLTS YOU NEED TWO PER BIKE. WILL ALSO FIT ATC AND TRX 70'S (53D) @ *REAR_SPROCKET DAMPER DAMPNER (CT70K0_TO_1982) all_ATC70'S CT70_SL70 XL70_CL70 SOLD_EACH 41241-051-000 7/21M (32D)SOLD EA, FOUR REQUIRED FITS ALL ct70 THRU 82. FITS ALL ATC70'S 32D