Yamaha 1800 svho sho ho rear of crank shaft .snout stator 

Google crank spine tool svho .coupler tool svho .some thing should come up .

I just used the same one but you can change it if the one way bearing wears it out definitely..The way Yamaha is these days you might be waiting a long time on parts they are terrible .

@@rickohlson3962 hi , thanks for your reply , the one way clutch is the reason I have pulled the engine apart , it is slipping .

@stgnsw No worries.it should be ok if you just replace the clutch .I should have measured the thickness at the time .

@@rickohlson3962 when I get mine apart I will let you know what condition it is in , it looks like the engine had water in there.

@stgnsw not good at all .the shaft should be the same thickness threw no dips .