Question for the old schoolers

Get to a shop that has either a K&L parts book or a sudco parts book or call carb parts warehouse I dont know the number but you could do a search . These companies sell alot of carb parts and air boots and stuff . Maybe you could find something there . Thats a pretty big carb for a 50 .It should scream .

Guessing a bit as the memory is fading. Old age...... I think the reed block (rubber part) off the YZ80 should fit. They had 26 mm carbs then and a 28 mm spigot will slip straight in. The manifold should only need a touch of grinder on the inside to remove a small amount of the rubber if there is any step inside the manifold I would also try to find the latest reed block that you can that fits into the barrel as Yamaha was constantly developing the technology then and blocks changed significantly from year to year. YZ50 parts are getting rare now. My dealer has one in not bad shape painted totally black, plastics and all. It could be worth while talking to Eric Gorr as well as he seems to know about weird things like this which were actually real common in the early 80's

Go to carbparts.com and give the guys a call. I've dealt with them b-4 with good results. They might be able to help. 216-524-1599