Replacement float seat

[mm1ut1]

I have a 79 special but with parts from different years on it. I have a leaky carb and after inspection I think probable cause is float bowl screws not tightened or possibly the O-ring on the seat leaks by. I inverted the carb and blew in the fuel line and it seemed tight after reassembled but figured I would replace the float seat. Can someone verify the year float seat pictured and recommend a replacement source ? Thanks!

[Schming]

The brass float is from '78-'79 early carbs also the metal float needle is too.
The early carbs also have a threaded float needle seat. The seat in your pic is from '80 and later carbs which have viton tipped float needles.
This may help: https://xs11.club/forum/repairs/inte...entifier-guide

[mm1ut1]

From the outside it looks like a 79, but the float seal says 80. Makes me wonder if it was from a different bike. . .My bike was restored by at least two different individuals. It did run strong before it started leaking.

[Schming]

If the idle mixture screws, on top front of the carbs, are recessed they are late carbs which are jetted a bit leaner and may not perform the best for the '79 SF.
They will work, but if it were me I would confirm the jetting and make sure they aren't running too lean.
My '80G runs 115 and 120 mains on 1&4 and 2&3 respectfully.
I believe that the '79SF has 137.5 mains on all 4 carbs.

[DiverRay]

Yes, earlier carbs have bigger main jets, but they share the jet! Later model carbs have main jet ONLY, so they are smaller.

[jetmechmarty]

Niche Cycle is a good place for genuine Mikuni parts, once you get it sorted as to what you need.

[cajun31]

From the outside it looks like a 79, but the float seal says 80. Makes me wonder if it was from a different bike. . .My bike was restored by at least two different individuals. It did run strong before it started leaking.

It would be a very good idea for you to post a set of good pictures of your carbs. Both internal with the float bowls removed and the outside of them front, back, side and bottom. We can better determine what you are dealing with by looking at what you have rather then guessing.