Bobber seat & Exhaust (rejetting required?)

(Second posting -> I accidentally put the original under 'projects' which I misunderstood what that actually meant; whoops!)

Hi everyone,

Crashed my bike (1980 kz440 LTD model A) ~ a month ago (no chevron signs OR stop sign warning...) and just finished changing the incandescent turn signals to LEDs with the electronic flasher relay, new tachometer, shifter and rear brake lever back in place, and other adjustments. While I was fixing the bike up, I was researching a lot (especially with the LEDs) and just noticed other people's posts on their bikes. Some were café racers, others bobbers.

I like the look of the bobber...but my question is: how do we know what solo seat will fit our frame? Is welding always required for the mounting plate to be secure to the frame? I'm worried about ordering something that won't fit, or will require me to take the bike to a shop and have them place it, but I also want to be safe.

Second question: I like the sound of the cocktail shaker mufflers, but can't find anywhere that goes over how one can decide if the aftermarket exhaust they are looking at will work with their bike without rejetting or tuning. I read somewhere that exhaust also creates important back pressure (I think?) and if you are messing around with it to be weary.
I mean, I'm sure for a perfect perfect ride, one would have to retune since you are changing how the bike was originally engineered to work, but is there a safe option?

Any advice/experience on both these?

Thanks for reading,

- Chris

Unless the seller specifies direct seat fitment to the model, then you'll probably have to do some welding or other fabrication. As to what style to go with, personally I prefer a cafe racer, since that's normally done to maximize speed & handling. A bobber usually kind of does the opposite. Dimecitycycles has a number of various seats, but I don't know anything about fitting them.

If you'll be keeping 2 mufflers, and the cocktail shakers have some baffling in them, then you may be fine. Can the baffling on them be changed? It would be handy if you could add some fiberglass packing or something, if necessary.

I just found out I can take a free welding training at my univeresity to receive a certificate and use the welding tools there (not too strict with personal projects)

The ones I am currently looking at can have the baffles removed if needed.
I guess I'll keep researching and asking around, thanks for the input!