rejet my xs400

Hi! i have a 81 Yamaha xs400 and i chopped the pipes so now i just have headers. i am getting popping sounds out of my pipes. I would like to know what size jets i should buy and if someone has had the same problem what did they do to fix it?
Thanks!

Put mufflers on it Cutting the mufflers destroys the bikes performance. There are threads on jetting where people try to run straight pipes. If you want the bike to run it's best, good or stock mufflers are the only option. I find the stock 80-82 style with the cross over pipe works very well for over all performance. Hope the mufflers where rotted out on your bike and you didn't destroy a good set of mufflers. You could have sold them for good $.

I went to 45 pilot 140 main jet.Fuel mixture 2 turns out.running nice no popping spark plugs look great.sounds bad pass.hope this helps.