Topic: 1978 CB550 K4 Been sitting a while

[BigAl]

Well, I got bored and found an old CB550.  Specifically a 1978 CB550 K4 with a little under 5,000 miles on it.  I think it has been sitting for maybe 30 years or so?  The gas tank was rusted paper thin and ended up in the trash.  Pity, I really wanted that tank, and a replacement is fairly pricy.  So I went with a cheap new tank in a shape that I never thought I would buy.  Instead of the nice teardrop shape I had envisioned, I bought something a bit more boxy.  It felt new and unusual for me.  The throttle would not turn due to the slide being seized in all four carbs.  Soaked them in acetone and they all slipped right out.  Took them all the way apart, soda blast, ultrasonic clean, new parts / screws / etc and I'm happy with them.  I took a stab at setting them up for pod filters, but after reading thread after thread of trouble with pods, I'm about ready to put the filter box back on and run the side panels instead of jamming all the electronics and battery under the seat.

The clutch was seized up, but new plates seemed to have done the trick.  Although it feels a little bit tight (as in it takes a little more force than I think it should with the clutch engaged).  I haven't tried to adjust it yet.

Currently, taken apart and sitting on my bench, is the master cylinder.  In the reservoir was what felt and looked like brown jelly.  So, I took it all apart, cleaned it up, brushed it out, and I think it is useable with a repair kit.  The bore is smooth but for the tiniest of a ghost of a mark where the plunger sat for 30 years. 

So here is my question.  I can buy a new MC for $60.  I can buy a repair kit for $60.  The price points don't make sense.  Is there a compelling reason to not just buy a new MC?  I will admit, I am the type of guy who has a bit of nostalgia for the original equipment, but it doesn't make sense to me that the reaper kit and new are the same price.

I'll see if I can't post some pics.

[BenelliSEI]

Good choice, my 1978 550K was one of my favourites! I’ve used a replacement master on my cb750K1. Initially, I installed it mid summer, to keep riding while I rebuilt the original. It works well, and I still have not rebuilt the original……

[Gurp]

All depends on what you what out of your bike.
if you want more of a resto, rebuild but it would be nice to get another to ride on and rebuild later.

[newday777]

I haven't used an aftermarket master cylinder yet, but hear they work OK.


Honda rebuild kit is $45 at South Sound Honda

https://www.southsoundhonda.com/--xpartsstream#/s/HOM//45530-404-315//1/y

[BigAl]

Thanks newday777, that is a parts site I had not yet run across. 

I have some POR tank coat coming in today.  Will get that done here this afternoon.  After that, there is no real reason why I couldn't start it up.

When I rebuilt the carbs I did set them up for a stab at pod filters, but am slowly changing my mind.  I'm not going to race the bike, just around town and the next town over.  In doing so I swapped for a bigger main jet, that is easily swapped back out, but I also raised the needles by 1 notch.  I do plan to replace the exhaust with a 4 into 1, the stock is old and rusty.  Maybe I can readjust the needle clips without deracking?  Can I scoot the linkage over enough to get at those 2 screws that hold the needle in?  Maybe it will be OK with the needle raised 1 with the more open exhaust running the stock airbox?

One more post after this one and I can start to put some pics up.  I take a lot of pictures....

[carnivorous chicken]

I used to rebuild MCs as a matter of course, but I've bought two David Silver Spares MCs -- one fore a 350F, one for a 550K -- and they have worked great. Downside is they look new compared to the rest of the bar switch housings, but you also don't have to risk rebuilding an MC and finding out it is damaged and/or still leakes, and then there's that damn clip you've got to fish out with a dental pick, usually corroded, sometimes broken off...

[calj737]

Enriching your needles probably won’t hurt overall as the ‘78 was setup to be pretty lean due to emissions changes. The main jet I’d drop back to stock. Plus with todays junk gasoline, I don’t think it hurts to be a tad richer…

If performance suffers or your plugs foul up, then reset the needles. A Spider Monkey might be able to get at the needles without pulling the carbs, but a Kansas farm boy has little likelihood 

[BigAl]

LOL, calj737, you are not wrong.  If I can't beat it out with a hammer I feel a bit lost...  I will give it a go with swapping the main jets back to stock and see how it runs.  I took a look at your build thread, very nice.  I initially envisioned a rebuild as thorough as the one you documented, but the more I get into mine, the more I realize that maybe this build should be my "learning curve" build and the next one can satisfy my desire for custom perfection (whatever that means).

Carnivorous chicken, yeah, that clip didn't want to come out.  I found that cussing loudly helped, and the blood let by the pointy tools I was using acted as a lubricant (and maybe a sacrifice to some motorcycle God).  The bore is pretty darn clean on the master cylinder, so I think I will rebuild it.  What you speak to is exactly what I am afraid of; a brand new mc amidst the patina of everything else.

Tank will coat today and I will let it cure for a few days after.  But, I should technically be in a position to fire the darn thing up next weekend.  To be honest, there is no real need to start it up.  It's cold here now, riding season is over, and I have quite a bit of work to do in order to have it ride ready anyway.  So why introduce fuel into a bike I'm still working on?  Well, because I'm not the sharpest tool in the shed I suppose, and I just can't help myself.

[BigAl]

Time to post a few pics, here is one on the way home from purchase.  Maybe, I can figure out how to attach a photo.....

[BigAl]

The carbs were pretty dirty and the slides were all stuck.

[BigAl]

More shots of dirty carbs

[BigAl]

Made the mistake of trying to put the staked screws back in and twisted one of the heads off.  Drilled it out, somehow without fouling the threads, and went back with hex head screws (with a little dab of blue locktite).  I know that the blue locktite will not prevent the screws from being removed because I took the whole thing back apart like three times.  The third and final time was because I forgot that little nylon washer in between the slide linkage and the carb body on #2 (on the common throttle shaft).  I managed to get that little washer where it belonged the first two times I put them all back together.

[BigAl]

Everything back in new including the pilot jet.  I wonder why they decided to press fit these later year carbs. 

By the way, I would put this all in one post, but if I try to post more than one picture at a time it fails (probably user error on my part).  So one by one I guess.

[BigAl]

Back together.  Happy with the results.

[BigAl]

Tank coating this morning.  96 hours of cure time.  So maybe next weekend for first fire.

[Stev-o]

Congrats on getting a 550...had one just like it a few years back.

[BigAl]

Thanks Stev-o, enjoying it so far.  I'll let the fuel tank coating cure all week long, it's a little bit tough to dump the excess out but I did the best I could.  Moved on to the master cylinder, it seemed to clean up really well.  I couldn't help but run it through the ultrasonic.  Dried it out really well afterwards.

[BigAl]

Moving on to the caliper, believe it or not the piston is stuck.  I put 120psi on it through the brake line fitting with the compressor and nothing.  Maybe soak it in acetone?  It worked for the carb slides....

[Stev-o]

Moving on to the caliper, believe it or not the piston is stuck. 

Not surprised!  If you had a good master cylinder you could most likely use hydraulic pressure to get it out.
I may have a spare if you are looking for one.

[BenelliSEI]

Moving on to the caliper, believe it or not the piston is stuck.  I put 120psi on it through the brake line fitting with the compressor and nothing.  Maybe soak it in acetone?  It worked for the carb slides....

Grease gun. Gently start a std grease fitting into the hard line hole. 1/2 a turn is enough, don’t strip the threads! Close the bleed screw and pump. It will come right out. For less mess, see next paragraph.

I took one of the original furl nuts off an old metal feed pipe and tapped it to take a grease fitting. Great tool, you generate 10 X the pressure of air and it walks out gently.

Next time you’re faced with stuck slides, just drop the carb in boiling water. Two minutes and the goo warms up and they slip out.

[BigAl]

BenelliSEI, that's a good idea, the thought never crossed my mind.  I dumped it into my old faithful paint can full of acetone.  It usually unsticks stuff that's stuck fairly well.  If that doesn't work, then grease gun it is.

[BigAl]

Finally got the piston out of the caliper.  Doused it in penetrating oil for a while and let it soak.  Gave the piston a few calculated whacks with a hammer, and then applied some compressed air.  That did the trick (I had the grease gun ready in the wings).  I cleaned it up with some dawn dish soap and a brass wire brush and then ran it all through the ultrasonic.  Turned out fairly well, I think it's clean enough and smooth enough to use.  So I think I will order out a new piston, rubber o ring, and bleeder screw.  Probably one new caliper bolt as well (one of the two was covered in a white dusty something, the other was clean as a whistle). 

I'm also tempted to order out new break lines, the whole kit with washers, banjo bolts, etc.  The pressure switch fitting looked good, the pressure switch itself has some crud in it but may still be good.  I suppose I can apply some pressure and check continuity with my voltmeter.  If they are cheap I may add one to the order.  We shall see. 

[BigAl]

I've been thinking about handle bars.  Initially I wanted to go with clip ons (no real idea how they install), but have been leaning toward clubmans (installation seems fairly self evident).  In reading through threads on the forum, a lot of folks say there is no need to adjust break lines / clutch cable / throttle cable to move to clubmans.  I guess I should figure that out before I drop bike funds on new break lines.

[calj737]

That white “stuff” on the caliper bolt is galvanic corrosion from the steel bolt inside an aluminum body. When reinstalling, smear some AntiSieze on the bolts and that will intercept the corrosion. (Your old bolt would clean up fine with some wire wheeling or brushing with a stainless brush. I use stainless almost exclusively dealing with these bikes. Won’t harm aluminum, won’t strip any coating from the steel bolts, and it’s super soft and non-corrosive. You can pick up the small wooden handled stainless brushes at any place that sells welding equipment.

The “clip-on” bars typically clamp directly to the top of the forks, either above or below the top clamp. Instead of clubman’s, take a look at “Street Superbike bars”. These are flatter than stock bars, not so uncomfortable as Clubman’s, and will install directly on your stock clamp. Norma nHyde “M” bars are very popular as a particular model. These bars are the style of modern “Hooligan” type bikes. Very sporty, comfy, and no changes to cabling required. You can get them in steel or aluminum, so colors abound.

[BenelliSEI]

Find a sharp tool (I use a dental pick with a ninety degree bend in the end) and really scrape out the seal groove. Particularly the inside, back corner you can’t see. The crust that builds up in there is hard to get out. If that groove is not spotless the seal will not sit back far enough. Your new piston will not slide in effortlessly and your brakes will “drag” and squeal.