I've owned crotch rockets in the past but recently purchased an 1978 CB400T earlier this year. It was in rough condition and almost everything had to be replaced or rebuilt. Finally got it done. Had sputtering and backfiring in the 4-5k range on full throttle. Did the ignition test per sticky in forum and service manual and pointed towards cdi. Got one from cdimagician now nice steady pull all the way to redline with no sputtering or backfiring, but seems to be lacking a little power. Believe it's fuel related and will have to play with the jets. Currently running 95 and 128. Here's a picture of it.