I got this:
https://www.themotorbookstore.com/genmotrepman.html

Probably not the same result you got. This thread is the first result on the first and second pages.

If it jerks and bucks while cruising at high speed, this usually means that the engine is burning fuel faster than the carb receives it (clogged filter, clogged gas tank intake, weak fuel pump).

Most carb rebuild kits come with a detailed parts diagram. Older carb rebuild kits are usually pretty cheap (less than $25). I think you can do the rebuild yourself. Just take it apart over a cookie sheet so just in case one of the little steel check valve balls/springs falls out you won't lose it. The usual suspects are dirt (spray out all passages thoroughly) a bad float, bad float valve and a bad accelerator diaphragm. Here's a quadrajet site with decent photos: https://www.vetteprojects.com/kstyer/quadrajet.htm

I agree with others that you should hold off on the carb rebuild until you have eliminated other possible problems (bad vacuum lines, ignition system problems).

I'll definitely consider major carburetor work as the last resort.

I am NOT confident that I can rebuild this particular carburetor, though I suspect I could rebuild another. I would still try it, the worst that can happen is I have to replace it, and it's not like I depend on this car as a DD (though I'm hoping to DD it if I get it in decent shape).

At the time I did the search this thread was the last result on the first page. Yay! We're becoming more relevant!

Nice. Found a service manual for 1980 Rochester Quadrajets. I'm still assuming I won't need it, but it's nice to have.

https://www.oldcarmanualproject.com/m...QJet/index.htm

Edit: And I found that through https://www.oldirononline.com

I know you are on a tight budget, but here is a guy I've used before (with fantastic results) for my Quadrajets:
https://www.thequadshop.net/

I've met Jim personally about 10 years ago, which is why I had him do the work, he won't do you wrong.

-Bob C.

Edit: p.s. have a look at this: https://valvoline.com/car-care/automo.../res20000718qj

Looks like we have something in common. I also had a '78 Yamaha XS 400 I bought new, but mine didn't have electric start.

If the car has been sitting for a while and the gas in it is old it could be stale or have collected moisture over a period of time. I'd suggest running the tank down as low as possible then filling it with fresh gas to see if that would help the starting and poor performance. Did you put anti sieze on the threads of the new spark plugs? If not I highly recommend pulling them back out and doing so. I had a plug sieze in my '88 Escort Pony several years ago and took all the threads out of the hole. I've used anti sieze ever since and never had a problem. I went and bought a tap with plans to try to tap the threads back in and the tap was to large to fit into the pocket where the plugs sit so I decided if a spark plug took the threads out maybe I could use the old plugs to retap the hole and it worked using lots pressure on the ratchet and going at it slowly. Just thought I'd throw that in just in case anyone else ever runs into a similar problem. It's much easier than replacing a head.

I remember that one...IIRC it was a special model so they could advertise a low price...plain wire wheels, no electric start, around $1000, I think. Mine I think was a gray market bike...it had an on-off switch for the lights, but bikes were already mandated by Federal law, I think, to have constant-on headlights. Mine was about $1200, which was a hundred or two below MSRP.

Bump.

Good news everyone! I replaced the fuel filter (quite a debacle thanks to seized corroded fasteners) and some symptoms are improved. It started more easily than it has in years and it accelerated smoothly to 60 with heavy throttle, not bucking at all.

It did stall when I stopped in Drive and it does still idle high but it's a major improvement.

Sounds like you're making progress!