Numerous 1982 GS550M Questions

[Squid_Girl]

Hey y'all. No idea how I haven't found this place before, I've been working on this old Katana since October of 2021. I got it from someones back yard, where it had been for a while taking grass clibbins and rain after the original owner peacefully passed away, it went to his son, and his sons wife eventually told him to move it out of the garage because it was taking up space only a few years before saying "You need to sell this if you're not gonna actually fix it." $100 down from $200 and a trailer later, I have the bike I'm working on now. Real "do-it-yourself punk" kind of vibe at this point, which I'm very proud of. Took about a year off but I'm back on my bs now that I got my garage put away in my new home.

I pulled the basically untouched 550 engine and found that the JIS bolts for the carbs on the cylinder head are seized seized, and there's 2 bolts I cannot get to unstick in the same part. Not even with the blowtorch, a can of PB, a dead blow, the impact, and some Harbor Break extractors. Everything is so aged that one of the screw heads snapped off when I was trying to remove it. One of the others made smoke when the impact finally got it to back off. As well, the pistons decided they needed more compression apparently and are covered in burn and I'm gonna have to soda blast them.

My questions I've been waiting to ask since mid-November 2021, and I do apologize for how many there are. I've just been doing this basically alone and with YouTube:

I have heard rumor of a GS650 top end swap, like pistons, heads, etc. on the crankcase of a 550. I'm already going to be replacing the cylinder heads and pistons and, considering the bike is an antique, I can find the parts I need relatively cheaply as long as I'm happy rebuilding them, which, most of the replacements I'm finding are cleaner than what I've got (The rear passenger cover for a 2022 Ninja from Kawasaki is $300, by comparison) so that's not really an issue. Also, can I use the Mikuni carbs from the 550 on the 650? Do I need to do anything to the gears? The cog? The sprocket?

There are a few deep-set screws in the Mikuni carbs I'm struggling to get out and I don't want to strip them. They're flat-head, and stubborn. Any ideas? I can replace the cylinder heads, but finding new carbs is not on my list of things I wanna do. I know I need to jet them, because I'm going from the intake Suzuki engineered to a way more openly breathing system, and I'm afraid I can't get to all the parts I need to get to in order to successfully jet the carbs. As well, the exhaust was mostly rust on the inside so the pipes were cut off at the weld that connected the headers to the trumpet and need to figure that out, as I'm sure nobody in the neighborhood will like me if I just straight pipe it.

If I put a front end conversion on, as I currently have a cable-driven speedometer what would anyone suggest for reliably determining my speed? I don't think the donor forks would know what cable-driven means. I'm concerned about the brakes, if only because I rebuilt them myself and this is my first time rebuilding brake calipers including polishing the internals due to having sat untouched for like, 30 years, so doing a swap is something I'm interested in but also hesitant about. I'm confident in my work, but there's also that loud voice in the back of my head telling me I did it wrong.

If anyone has used the m-unit, what was it like? I see this accessory called like the m-unit switch and it's supposed to minimize the wires running or something and I do not get how it works other than magic. I'm not concerned about cable management, I found these awesome sleeves that work like finger traps that completely fit the color and aesthetic of my build and am actually looking forward to a lot of cabling to add decoration as there's a lot of dead space now with the stock air box hemorrhaged in to a dumpster (honestly, 99% of the parts I'm finding online are in better condition than what I'm pulling off). If you had to build an under-seat tray for the electrical system, how did you build it?

I'm also swapping over to a lithium ion system but that's another post later about regulators and rectifiers.

On a lighter note to introduce myself, the bike was about $2,600 new in 1982 which is about $9k today, which if I don't count the tools I've had to buy to do some of this work, by the end of this rebuild I'll come in maybe just under! The bike and the whole project means a lot to me, obviously, or no person would be doing this. I've also been told I did amazing work painting my fairings and wheels with rattlecans and 2k automotive clear coat. Had a custom seat cover stitched in England, brake lines from Germany. Truly, a labor of love.

If you can only answer one or two, any help and input is greatly appreciated!! Stay wild, y'all

Edited: Is 650 the biggest I can fit in this thing?

Edited August 11, 2023 by Squid_Girl

[wraith]

Welcome to OSS, that's some intro 

Where to start  yes the 650 top end will go straight onto your 550 bottom end. I've done two way back in the past but some 550 engine top crank case needs open up a bit to fit the 650 barrels on and some don't  ever use your 550 cams or if you use the 650 ones change the cam sprockets over. 

Yes you can use the 550 carbs on the 650, and you will need to rejet anyway it you putting a different exhaust etc on. 

Not used a M unit but lots on here have. 

There has been a very recent posts about reg rec and battery so have a scroll down and have a read  

As to front end swaps there are lots of options bending on your skill and cash. Lock stops maybe your biggest problems as new ones will need to be made but Suzuki are good as most early gsxr to bandit (with stem change) to later gsxr will all fit. You will also want to look at changing the rear to match. 

Bigger than 650, you could get a 650 big bore once but not 100% if you still can, you can fit gsxr/gsxf 750 engines in the 550 quite easily. 

Have a look through the project section and you will get lots of info and ideas and you can then ask even more questions 

Start a build thread in the projects section with lots of pics (we like pictures) and you will get even more help