CB550K1 - that Gulf bike

[Ringo]

Scored this old thing. Some hack did a little work to it…at least an alright base to work from. We’ll see how it goes.

So here’s the original thread. It’s a long and winding read. I’ll summarize what has been done already and where I’m looking to go a few posts down..

'75 CB550K1 Gulf - Round...3, the fun stuff

Picked it up yesterday. It's a sound runner, in good tune. The plan is to do a ground up build, completely strip everything and start from scratch. I haven't decided on color or well anything yet. Wish I had more to report at the moment, but I figured I'd just get my build thread started...

www.dotheton.com

 

[Ringo]

Tough crowd. Alright it’s me, I’m the hack (literally). I stumbled my way through building this bike with the help of this forum a decade or so ago. Then sold it shortly after and have regretted it since. A couple months ago I was given the opportunity to buy it back and you bet your ass I did.

Can’t tell you how happy I am to see this thing in person again, and ride it! It’s actually not the death machine I had convinced myself it was. Seller’s remorse justification? I don’t know.

It arrived running on 3 cylinders and sounding bad. But it turned out to be an easy fix—I’ll get into that later—and it’s running great now. That said, I’m not done with it. There’s a lot of stuff I had planned and never did, so it looks like this winter will be busy.

I’m excited to be back here, see a few old faces.

 

[Maritime]

Ha. Welcome back! That is still one of my top favorite bikes from any DTT member!

 

[pidjones]

Tough crowd. Alright it’s me, I’m the hack (literally). I stumbled my way through building this bike with the help of this forum a decade or so ago. Then sold it shortly after and have regretted it since. A couple months ago I was given the opportunity to buy it back and you bet your ass I did.

Maybe (at least for me) hesitant to follow the "hack" comment, as at least on first glance it looks quite right. Do you have any changes planned or in progress that you care to clue us on?

 

[irk miller]

Great build from the start. Nice to see you get it back. I had a chopper come back into my garage that I had sold 3 years before. I tried to get it back, but the guy hadn't finished ruining it yet. Glad yours has stayed mostly intact.

 

[NSNickName]

I am one man who understands sellers remorse! Beautiful bike.

 

[Ringo]

Maybe (at least for me) hesitant to follow the "hack" comment, as at least on first glance it looks quite right. Do you have any changes planned or in progress that you care to clue us on?

The list will evolve as I get into it, but right now I know it needs new valve guides and seals, and I probably ought to just go new valves and heavier springs too. And sheesh maybe a light port job. I forget which cam I installed the first time, but it feels like it wants to breathe better at higher rpms.

I definitely need to find some lighter rims too. I had no reference for how heavy the stock hoops were last time I owned this bike, but it was the first thing I noticed when I rode it a couple days ago.

Ergonomics- I’m not sold on how I had it set up before. Might take some creativity as i didn’t give myself any options for peg mount location.

lots of other little things, and a full stainless exhaust that I can use as the perfect excuse to finally buy a tig welder!

 

[Ringo]

Ha. Welcome back! That is still one of my top favorite bikes from any DTT member!

Hey Mike!

 

[Tim]

Glad to see you and the bike back! I've been thinking about chasing my XS that I sold down and buying it back for 1/2 of what I sold it for

 

[Ringo]

Glad to see you and the bike back! I've been thinking about chasing my XS that I sold down and buying it back for 1/2 of what I sold it for

Well it seems like the cafe craze is finally winding down, so, buyers market baby!

 

[Ringo]

Great build from the start. Nice to see you get it back. I had a chopper come back into my garage that I had sold 3 years before. I tried to get it back, but the guy hadn't finished ruining it yet. Glad yours has stayed mostly intact.

Thanks, yeah it’s virtually unchanged from when I sold it. Couple nice new machined parts that the owner finished but that’s it. Stoked.

I am one man who understands sellers remorse! Beautiful bike.

Thanks dude!

 

[john83]

Cool to see it back with the original owner!


Sent from my iPhone using DO THE TON

 

[Ringo]

Merry Christmas or whatever you celebrate you degens!

So, shortly after I received the bike, I bore-scoped the cylinders and found oil in all cylinders. After I took it down to the frame and removed the engine, I pulled the head and jugs…and had to walk away from this project for about a month because it just became much more expensive.

When we overhauled this engine a decade ago, we didn’t replace the rockers, as they looked almost mint. Well, it seems they weren’t, and they’ve ruined our nice hot Webcam. Two of the cam journals in the head are scored as well. There also appears to be rust pitting in one cylinder wall. F*ck. They’re already bored to the max.
As for the oil in the cylinders that I was originally worried about, I assume it’s coming from leaky valve guides/seals. Least of my worries now!

I’m a little demoralized by all this. There’s probably less than 1000 miles on this engine rebuild. But ultimately I guess that’s why I bought this bike back-to fix all the corners I cut when I was young and dumb. (I’m still dumb, just less young)

In other news, I’m almost done redoing the all the shitty frame welds I did originally. It’s slow going since TIG is the only welding process I’m set up for now, and arguably the wrong process for welding dirty metal that can’t be properly cleaned. Nevertheless, I’m ok with the results I’m getting.

 

[teazer]

Pistons are bore look fine from here. The crowns will clean up ok and that minor rust pit in the liners is low enough to make very little difference - unless you are thinking of going larger bore anyway. If you go much larger on the bore you may have to consider a 650 top end to get enough air in.

But unless that's where you want to go, try to use what you have. Shops like my guy in Australia 2 decades ago or Pete Fischer at Powroll ( I think that he may have crossed the rainbow bridge too) those guys used to be set up to line bore the head and cover to take split bronze bushes. See if there's anyone that can do that.

The cam and bearings don't look too bad depending on your planned next steps. They show wear and rust pitting and so on but are probably usable without losing much power or longevity. Of course it would be better with all new parts, but you might be surprised how worn parts can be before they absolutely have to be replaced. That's why I tell people not to pull a crank out if the bike is running just fine. Once you see wear and pitting, you cannot unsee it. If you want to replace/repair parts and have the budget or a good source of cheap replacements, don't be too much of a perfectionist.

If parts are way out of round or lost oil pressure or compression is low, that's different. Oil seals on the guides? Go for it. Wear in the guides? measure it and see if it's still in spec. I like everything in a race motor or a bike I am selling to be first class, but there are limits for a reason....

Irk knows what bits go together on those motors and might have some ideas.

 

[pidjones]

Don't know about a 550, but I ruined the right head and cam on a GL1000 last summer (total loss of oil caused by a &*%#@ PO's use of RTV), ebayed another for $100 and transfered over valves (new) and springs. Running smooth now.

 

[Ringo]

Pistons are bore look fine from here. The crowns will clean up ok and that minor rust pit in the liners is low enough to make very little difference - unless you are thinking of going larger bore anyway. If you go much larger on the bore you may have to consider a 650 top end to get enough air in.

But unless that's where you want to go, try to use what you have. Shops like my guy in Australia 2 decades ago or Pete Fischer at Powroll ( I think that he may have crossed the rainbow bridge too) those guys used to be set up to line bore the head and cover to take split bronze bushes. See if there's anyone that can do that.

The cam and bearings don't look too bad depending on your planned next steps. They show wear and rust pitting and so on but are probably usable without losing much power or longevity. Of course it would be better with all new parts, but you might be surprised how worn parts can be before they absolutely have to be replaced. That's why I tell people not to pull a crank out if the bike is running just fine. Once you see wear and pitting, you cannot unsee it. If you want to replace/repair parts and have the budget or a good source of cheap replacements, don't be too much of a perfectionist.

If parts are way out of round or lost oil pressure or compression is low, that's different. Oil seals on the guides? Go for it. Wear in the guides? measure it and see if it's still in spec. I like everything in a race motor or a bike I am selling to be first class, but there are limits for a reason....

Irk knows what bits go together on those motors and might have some ideas.

Hey teazer! Thanks for talking a little sense into me. No plans to increase the bore, I think I’m pretty much at the limit already and I’d hate to turn those nice pistons into paperweights. Would you do anything on those pitted lobes to prevent trashing the new rockers? Carefully taking some rough edges down maybe? I know this isn’t the right answer, but what do you think about TIG welding the pits with some hard facing filler, A73 rod maybe?

I have limited time to devote to this thing, this winter, so I snagged a nice head, cam, cover w/rockers and spare set of NOS rockers. I think I’ll install the stock cam and the better of the two heads this winter, and set aside the NOS rockers, webcam, and other head for a full rebuild + light porting…maybe.

Those split bronze bushes you’re talking about, I like the sound of that! Probably going to be a next year thing with the rebuilt head. But those would be slick…hah.

 

[Ringo]

Don't know about a 550, but I ruined the right head and cam on a GL1000 last summer (total loss of oil caused by a &*%#@ PO's use of RTV), ebayed another for $100 and transfered over valves (new) and springs. Running smooth now.

Gotta love eBay, I got lucky today finding everything I need to fix it!

 

[Maritime]

Nice

 

[Ringo]

Some progress lately. All of the frame welding is finished. On the first go around, I left everything very unfinished in places that were covered by the seat. This time, I completed the job by boxing in everything that was open, reinforcing (or redoing) welds and adding the top gussets, footpeg bracket mounts, and swingarm spool mounts.

The engine is coming along. The old head and cam are packed away until I decide what to do with them. The new ones cleaned up nicely; I stripped the head, blasted it, lapped the valves and fitted new guide seals. The new cam was stored with the old; I found a cb650 cam in great condition, so at least I don’t have to go back to a stock 550.

So part of my larger plan to chase oil leaks includes HD cylinder studs, and of course I sheared off the very first stud I tried removing. Heat, penetrant, double nuts, vice grips…nothing. Locally I cant find a stud extractor for studs under 1/4” so I’ll have to find something online. Any recommendations??

For rims, I went with 2.5” and 3.5” both 18” dia. Metzeler Lazertecs we’re absolute bears to spoon on.

 

[Ringo]

I didn’t get any photos, but I serviced the forks too. New 15wt fluid and race tech springs. I went a little bit heavier so I can back off the preload to race tech’s recommended spec. I also increased the compression damping in the race tech gold valves by one turn. The bounce test feels very nice now, road test later.

Oh I also sent the brake rotors to TrueDisk for some weight loss. Taking them from 7mm to 4mm, per the guys over in the performance section at sohc4.

Couple more pics. And some of the original rats nest that prompted all this welding…