92KK 84WW Olaf
Life time member
Number of posts : 7955
20 spline refers to the final drive end. The gear box end did not change. Be aware you can actually buy a new splined end for 20 splie shafts and have it welded on to the drive shaft at a machine shop.
At 1985 you may have a 16 spline shaft, you need to check this out more. If you do, they can be harder to find. I have 2 Ks on 16 spline final drives but also have 2 31/11 ratio spares for them.
You can find a 20 spline final drive and 20 spline shaft and just pop them straight in. Mostly the final drive ratios are 31/11 for RS and 32/11 for RT/LT. Its a small difference and I would go on condition/price rather than focus on the small difference in the ratio. A K75 one for rear disc brake will also fit BUT the ratio on those is usually 32/10 but thats a bit out for you at 10%. The ratio is stamped on the top of the final drive casing.
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1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles.
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles
Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500