Carb confusion...

[sir_h_c]

I have a 1980 sg and I'm having a hulluva time getting it started. When I bought it the guy had it running and I even took it for a spin. With the bike came an extra set of carbs with a broken post, but good for spares(except they are a different model?)
When I got it home I took the carbs apart for a good cleaning and bench sync and I haven't gotten it to start again. My fear is that the carbs on the bike are from the pre 1980 model and the busted ones I have are the correct ones for the model.

q's
Can the carbs be interchanged? Can I use the earlier carbs on my 1980 or do I need the the appropriate ones fixed? How do I tell for sure which model I have. (I'll try to get some pictures up this evening) The thing that tipped me off was that the idle screw is different on the 2 models... The one on the bike has the long adjustment screw that turns from the top. The spare has the short adjustment screw that turns from the bottom(attached to the bracket with an extra little metal bracket)

Help!

 

[sir_h_c]

also, how necessary are the brass plugs over the pilot jets? between the 2 carbs I have none!

 

[xschris]

You can run 77-79 carbs on a 80-82 xs 400 sohc I have done it and they work fine. You don't need the brass caps on the 80-82 pilot mix screw in order for them to work. If you are running the 77-79 carbs make sure the pilot mix screws have not broken off it there holes it is a very common problem with these.