CB550K1 - that Gulf bike

I took another stab at the cylinder studs, with a little hatred this time. I bent them over at the base which gave me some solid leverage, and most eventually twisted out this way. A handful snapped off, and I welded old studs onto the ends protruding from the block. Most took a few cycles of welding/breaking/welding to come loose, and two of them I had to just hold the TIG torch on them to get enough heat down in the threads to break the bond. But they all came out.
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Pistons got cleaned up and new rings installed. The cylinders got a light hone as well, while we’re on the subject.
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APE cyl studs and pistons in their places. I will say, using APE’s recommended torque of 20-22lbs when torquing down the head had my skin crawling a little. That feeling when you know you’re going too far…you’re amazed the threads are doing what they‘re asked by the torque wrench. Twelve of those feelings.
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Jugs installed
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Head and 650 cam in place.
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An interesting find in the oil pan. Sand. A fair amount of sand. This baffles me—there’s been no sand anywhere near this engine while it’s been open. Maybe carelessly removing the oil fill cap with debris stuck around it? But still, it’s a lot of sand for that. Oh well, cleaned out and moving on.
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The stock carbs are really just a clusterfuck, aren’t they? It has me thinking about alternatives. So I’m not going to do anything with them right now, I might not even install the new ITG filter—it’ll just get smashed against the frame down tubes.
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I hate to say it, but I think I’m going to go back to a stock sprocket cover. It works a little better with the bike, visually. Sorry Lee!
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And lastly I fitted a new Hindle exhaust. I’m still planning on making a stainless exhaust myself, but don’t have time this year. Still have to figure out an end can, and modify it a hair to clear the side stand mount.
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The stock carbs are really just a clusterfuck, aren’t they? It has me thinking about alternatives.
I run the dual carb setup for the 550 from Murray's Carbs. Twin Mikuni VM34. He ditched the welded intakes for cast intakes, so now they're a much better fit and finish. I love what the setup does for these inline fours, especially on the bottom end.
 
I run the dual carb setup for the 550 from Murray's Carbs. Twin Mikuni VM34. He ditched the welded intakes for cast intakes, so now they're a much better fit and finish. I love what the setup does for these inline fours, especially on the bottom end.
That’s a neat option. From the photos on his site, it looks like the 2-1 manifolds clamp on to the stock intake runners? How’s the throttle response with that? I’d like to shorten the runners anyways, whichever route I go, so I’ll probably fabricate them. There’s a couple cool setups with four vm26/28s over on sohc4…buuuut I just keep circling back to “why am I doing this to a slow old bike?”

I was just looking at prices on CR carbs. They’ve almost doubled since I last owned this thing!
 
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That’s a neat option. From the photos on his site, it looks like the 2-1 manifolds clamp on to the stock intake runners? How’s the throttle response with that? I’d like to shorten the runners anyways, whichever route I go, so I’ll probably fabricate them. There’s a couple cool setups with four vm26/28s over on sohc4…buuuut I just keep circling back to “why am I doing this to a slow old bike?”

I was just looking at prices on CR carbs. They’ve almost doubled since I last owned this thing!
Twin VM34s with a well tuned intake should get you a slight hp bump- maybe 2- 3hp, plus better low end torque. They're very happy cruising 55 - 60mph. It's a worthy argument to question the investment on a vintage bike, but to me just the ease of maintenance would be enough to consider the option. I absolutely despise the Keihin 4 carb racks from the 70s. Add in a better throttle experience for the VM and it's an easy decision for me. I've done it on 3 Honda inline 4 engines so far. I'll probably do it to most every one I build. If you can make your own intakes, that covers half the price. I love the performance of the VM and TM on the overhead cam engines.
 
I also had a Murrays dual Mikuni setup on a CB550 and loved it. So much easier to deal with, started on 1st kick every time and better bottom end throttle response. They're not cheap but my OEM carbs were pretty worn out and it was worth it to me to have something much easier to deal with.
 
Interesting, thanks, I’m going to look into this. Did you guys run pods, or make an air box? Did it alter the intake sound? Got any pics of the set ups?
 
I'm running UNI filters, which I prefer over most. I've also run them with the K&N oval filters.

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Sorry for the lack of updates, I took a few months off when work got busy. But I’m back at it again until April or so.

I decided to stick with the stock carbs for the time being—it would be really nice to have this thing running this year. I did pick up an ultrasonic cleaner though, so cleaned and fully rebuilt the carbs. I’m sticking with the same jetting, despite the cam change and larger exhaust, neither of which are drastically different from what they replaced. Hopefully it only needs some fine tuning, we will see.

I also bit the bullet and tackled the wiring. The stock harness was pretty hacked up by the PO and myself, so I went for a fresh start. There are several good wiring diagrams out there for this bike, but they weren’t much help with the state the harness was in, so I had to do a lot of tracing individual wires around. I then built a simplified harness with only the circuits I need, and since it’s much smaller, why not overbuild it and use larger gauge wire? So I did, and I soldered every crimp, and now instead of being the weak link in the build, the electrical system might be the most bulletproof part of the bike!
Side note: while replacing the stator wiring, I discovered there were no screws securing the stator to the cover! Luckily it did not grenade in the 5000 odd miles it was floating around. Jeez 23 year old me…#&$@!

A big part of this rebuild is dialing in the ergonomics and handling to better fit my wants/needs. I’ve addressed the peg position, front/rear suspension, and made the first adjustment of geometry by lowering the front end. That leaves bars: I tossed the eBay clip ons in favor of some Tomasellis with more adjustment than I need. I’ll need to fine tune the position I’m sure, but as a bonus they can be positioned out in a way that gives me more leverage to turn, making the steering *feel* quicker. This puts my hands a good two inches more outward, in line with modern sport bikes.

Next up is fabricating mounts for the battery, r/r, and starter solenoid in the tail. And starting to wrap my head around some sort of gauge cluster…
 

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I would guess by dropping the front end you did more to quicken the handling by reducing the trail than the wider handle bars. Although the wider bars will give you more precision at the expense of larger distance in the swing but that wont make the bike turn faster. Have you measured your trail? its never a definitive answer on how good a bike will handle but it always makes for a good apples-to-apples comparison from where you started.

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All good stuff doc_rot. I haven’t measured trail yet—I don’t have any baseline for geometry/suspension at the moment, other than my initial impression ride when I bought the bike back. We’re still basically in the mock up stage, but luckily I’ve got lots of height adjustability in both front and rear. Not taking into account fork position in the clamps, I’m actually up in height in the front compared to before, but just by millimeters: I went down an inch in rim diameter, but gained more in tire profile! The front will likely need to come down quite a bit more.
 
I’m also not running a steering damper any more, so I’m not looking to go ham.
 
I’ve been busy in the garage but slacking on the pics and updates. I just don’t really like sharing stuff about me online these days. Social media kind of ruined the internet in my eyes.

Anyways…

I made a battery box out of some aluminum angle. The reg/rec mounts on top, and starter solenoid in front. Should keep everything secure.
Also credit to Shorai here: the old battery is 13 years old and never had its cells balanced and still cranks the engine nearly as fast as the new battery! It’s still getting replaced though, because age, and Shorai makes the same battery but way smaller now.



Next up was the seat. I originally built the seat to hinge up in the back for quick access, but never followed through. Instead I just drilled a hole in the middle of the seat and bolted it to the frame. Past me sucks. Present me eventually got it to work though.

I had to reinforce the entire seat with fiberglass, as well as aluminum where the hinge mounts. I chose a spring-assisted hinge because I hate myself. I thought it would be cool to have the hinge assist with lifting the seat, but it doesn’t. It did make it a nightmare to bolt the hinge in place.

To lock the seat down, I wanted something faster than a bolt. I discovered McMaster carries locking pins, and collars for them, so that’s what I did. It was difficult to get and keep the pin and collar perfectly aligned, while adjusting the hinge, but we got there. See photos, they explain it better than me. There are undoubtedly better and cheaper ways to do this, but tunnel vision plays an oversized role in my daily life.
 

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Couple more pics.
 

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