Topic: '71 cb350k, '77 cb550f side by side refurb

[geoluv]

I picked up two old cbs the other day.  A '71 cb350k (twin) and a '77 cb550f super sport.  Got the cb550 for $430 on eBay, clean title, not perfect, in normal cb shape, missing the left side cover, ignition hacked off, pretty clean frame and wheels I must say, carbs seem pretty clean too, tank just needed a splash of acid to clean up nice, and missing the airbox from the boots back unfortunately.  I could probably just throw gas in it and run it but I'm going to do the top end on it and maybe port it and install a 650 cam I got for my cb550k0 that I got 3 hears ago.  After I won the guy told me he had a cb350k that a buyer flaked on, and we agreed on $700 for the 350 that was in much better cosmetic shape than the 550 and not missing a side cover or airbox pieces.  Again clean title and just needs the top end done. 

Here are the links to the listings if you want to see them, click on the pictures to see the original listings:

https://www.ebay.com/itm/1977-Honda-CB-/123182955883

https://www.ebay.com/itm/1971-Honda-CB/123173092098

My goal is to sell at least one of the 550's and keep the 350.   

[minimo]

Great deals! Good job. Average Los Angeles Craigslist price for the 550 would run at least six-times that amount.

[geoluv]

Update:

The wiring on the 550 is kinda hacked up.  Looks like someone installed underglow on it about 12 years ago and did a pretty bad job. Ignition terminals cut off.  When I hot wired it nothing turned on.  I have my multimeter ready next time I visit my garage.  Also have a spare ignition barrel from a ‘74 550k that I’m going to use in the interim.  Thing is it’s only got 4 wires and my ‘77 has 5 wires going to ignition it seems, but just to get it going I should be able to twist the two brown wires together and jam them in the same terminal.

The 350 is coming along much smoother.  Everything lights up and honks properly. The starter cranks strong and doesn’t make any funny noises.  Not spark to the plugs it seems but the points spark when I arch them with a screwdriver.  I think they just need to be cleaned but I didn’t have any sandpaper.  I’ll bring some 400 grit and a business card next time I go back.  Once I get spark all I gotta do is slap the carbs back on and fill her up with gas which leads me to my next issue:  the gas tank is totally f@?ked up. 
Not sure when but some PO tried to clean the inside with what I assume from smell is TURPENTINE and just left like two gallons of that s#!+ in there!!!!   I could seriously kill that SOB.  The tank is beautiful and clean on the outside, no dents and matches the side panels and is still glossy.  The inside has a pretty serious layer of rust.  Turpentine is mostly water. Had the PO simply left the tank alone or simply drained the f$&@ing turpentine our after his dumb a$$ tried to clean the tank with it it would have had only a minor case of surface rust; easily removed with a quick splash of muriatic or phosphoric acid like I did with the 550.  But because it sat with what is essentially water in it for the last however many decades it built up considerable rust.  I filled it with muriatic acid for a few days. Problem is there is so much rust it neutralizes the acid and the acid stops working after a while.  I strain it and put it back in and it is slowly eating away at the rust.  There is pretty much just a ring of gunk where the turpentine water level was left, I’m going to drain the acid and put a few cups of sand in the tank and some water and slosh it around to try to grind off the last thick rusty parts inside the tank.  After that more acid.  I’m kinda afraid the rust ate through some of the welds because I think I spotted a place where some acid was leaking out this morning, but not sure.  If it’s minor the red kote should plug it if it’s bigger I’ll weld it or braze it or something.  The 550 has a hole in the tank too but it’s on the flat part on the underside, someone already patched it with one of those epoxy kits.  It will be easy to weld a patch on. 

[geoluv]

Got the 350 sparking strong, just needed the points and plugs sanded a little.  Carbs seem to be in good shape I am going to rebuild them today.  The tank I’ve almost got cleaned out.  It took an initial round of sloshing around nails in it to break everything up, then several soaks with muriatic acid, then sloshing around sand and water inside it to get the last of it.  After I get it clean with the sand I’ll hit it with one last slosh of acid to get the all the flash rust from the sand slurry then fill her up with gas and see if she fires!

[geoluv]

Got the 350 firing and rolling today.  Sanded and buffed points and plugs. Did a cursory inspection of the carbs, checked the diaphragms for tears, made sure everything was sliding without too much resistance and that they weren’t missing anything and that the jet holes were clear.  They were is pretty crusty condition honestly.  But everything was there and moving right so I slapped everything back in the bike with the very dirty stock air filters.  I got new clear fuel line.  The tank still has some pockets of rusty gunk inside that scrapes off easy if I can reach it but I can’t get at most of it.  If I had it my way I’d use a plasma cutter to cut out the bottom of the tank, clean everything, then weld it back together in 1 hour instead of wasting days on this tank but I don’t have the equipment.
Anyway I really want to see if it fires and ride it just for a second so I know if it’s worth ordering parts and rebuilding everything.  I slapped the tank on and figured the screen will get most of the gunk and I’ll only ride it for a second.  It fires up after a little bit of hitting it with the starter.  I hit the starter in intervals so I don’t fry it.  It idles great and I take it for a ride, it pulls very hard on the low end compaired to my 550k0.  I get it about 5 blocks away and it dies. Won’t start.  The gunk is clogging the screen.  I could seriously murder whoever put turpentine in that tank!  Other than that it seems fine.  Lots of rattling when I hit the starter initialy, could be loose cam chain. I plan on keeping this bike so I’ll probably do the top end on it sometime soon. 

Here is a picture, ignore the long cables the bike came with big bars on it pulled back the previous rider must have been very small.  The bike has a longer front brake and clutch cable.  I installed euro bars that I had laying around and it looks great!  Tomorrow more energy and time dedicated to getting the inside of that tank clean and ordering parts. 

[geoluv]

I’m planning on cutting out the bottom of the tank Monday afternoon and mig welding it back together after I clean it out.  I have a mig welder lined up I just need to find a plasma cutter or an acetylene torch with a very small head.

[geoluv]

Scratch the last post I was able to get the tank totally clean or it seems that way.  Final mix was 2/3 water, 1/3 muriatic acid and some sand.  That seemed to get the inside spotless after all the initial futzing.  But I found out once I got all the rust removed that the rust had gone all the way through on the bottom in 8 different places where pin holes had formed and some place under that back mounting plate that slides in the rubber holder under the seat.  Either a pin hole formed under the plate or It rusted through at one of the tack welds holding he plate to the tank.  I could have waited til Monday to mig all the pin holes shut and mig a weld around the edge of where the plate touches the tank ooooooorrrrrr I could just run to advanced autoparts and get the $6 tank patch putty.  Guess which one I chose:)  I really want to ride this thing:)  I figured if the putty doesn’t hold I’ll burn it all off on Monday and mig it properly.  I sand and clean all the pin holes after I drain the tank and patch everything and put a bead of putty around the mounting plate.  That was hard because on the back side your fingers can’t fit in the crease so I had to use a screwdriver to pack the putty in the crease, see photos.  To my surprise everything holds water when I test it.   I’m afraid more pin holes are going to form or I’ll find more later,  I’m going to use some red kote soon and hopefully that will stop pin holes from forming. 

[geoluv]

Rode it around yesterday and its was backfiring and bogging really badly when i gave it the beans and it idles high, around 3000.  I yanked off the carbs and cleaned, rebuilt them and bench synched them.  I noticed two things that were concerning: the float needles were two slightly different models but they both fit.  The air screws are also two different models and neither are the correct model although they thread in just fine.  The needle point on each air screw is different too, and i noticed there was no o ring or washer that came out, the diagrams say there should be a washer and o ring in there too. 

the float needles don't matter as long as they are the same length and you set them both at the same hight (26mm).  Those don't concern me.  I also noticed one muffler had a baffle and one didnt.  i couldn't unscrew the retaining bolt to remove the other baffle because it was so rusted so i just ripped it out like the hulk. 

After that i slapped the carbs back on and drove it around, it didnt backfire at all even when i was trying to make it backfire. It still was idling high around 3000 though.  Could it be the incorrect air screws?

Im thinking about just getting the bootleg mikuni carbs off eBay:

https://www.ebay.com/itm/Pair-Carburetor-For-Honda-CB350-CB350G-CB360-CB360G-CB360T-CL350-From-CA/292392288731?hash=item4413f041db

Problem is i can't figure out what model Mikuni VM carbs those are supposed to be, how do i jet them? 

[jakec]

Better to just fix the carbs you have, or if the bodies are busted in some way then buy a new one on ebay. I had a 350 twin with a stuck/mangled jet and I bought a carb body for $30.

[geoluv]

I think I nailed down the idle issue.  Slow jet on carb 1 was defective seemingly from the factory; stock Keyster jet but the hole was kinda smaller than the one in carb 2 and crooked and not centered.  I checked that I could see light through it during the initial rebuild of the carbs but id didnt really notice that one was smaller than the other or off center.  They are very small and hard to see and I don't even need glasses.  It was easy to miss.  Im sure defective Keyster jets are rare compared to modern reproductions.  Did someone put 24,000 miles on this thing without it ever being able to idle correctly from the factory?  Maybe. 

New slow jets, air screws and o-rings as well as Pamco ignition, new plugs, caps, and chrome euro bars coming in hot from 4into1:)  I can tell I'm going to love this little bike as soon as I get it to fall back to idle correctly.  My 550k falls back and idles so smoooooooth at 900-1000 even with stock points. Might just give in on the mikunis if the new slow jet doesn't fix things on the 350.  only other thing I could think of is intake boots but i inspected those pretty well i don't think they are the issue. 

As for the 550f I am quite pleased with myself.  I wired on my spare ignition barrel and she fired right up after I rebuilt the carbs and kicked her for half a minute.  A running 550f with clean title for $430 in the north east, I'll take that any day.  Someone really did a number on this poor old girl though.  The ground wire to the battery is inexplicably hacked in the middle and spliced very poorly with a lower gauge wire.  It has 3 champion spark plugs and one correct NGK plug.  Gaps all over the place.  Seat shredded but nicely held together with black duct tape at least.  Poorly installed underglow.  Im spurised the carbs had all their correct pieces in place.  And someone was either addicted to burnouts (how?!?) or trail braking because the front tire is almost new but the rear is roasted. 

[geoluv]

Switching things to the 550 I'm at a road block.  The tank has pretty bad pinholes, some bigger than a pin hole really, maybe call it an ant hole?  Take a look at what I found after 20 min of scraping all the JB weld off the bottom.  It was leaking anyway. 

Luckily my brother welds pretty good I'm going to try to weld a plate on over the big stuff, use POR to paint over the entire bottom of the tank after I strip it with gel airplane paint stripper then kreem the inside and see if it holds gas.  It sucks 'cause this tank had just one small dent I could have filled it easily and I have the means to paint it the correct candy presto red.   If anyone knows where to get a cb500 or cb550 tank with no dents and a clean inside for a decent price let me know because right now I can't find any.  Are reproductions available?  I see they are for the 400f, the 750 both styles, the cl350, but I can't find the 550.  Seems odd they would make all the others but no 550.

These damn tanks are sucking all the fun out of these projects and racking up considerable hours I hate working on tanks so much.

[Stev-o]

Nice 550F tanks can be difficult to come by. FYI - the '77-78 K models are basically the same tank and can be easier to find. However, the petcome is on the opposite side.
Start a thread in the parts wanted area, someone has got to have a spare.


https://www.ebay.com/itm/1977-HONDA-CB550F-SUPERSPORT-CB550-CB-550F-F-GAS-FUEL-CELL-TANK-GASTANK/371752840018?hash=item568e322b52%3Ag%3A-k8AAOSwOyJX8spc&_sop=16&_sacat=0&_nkw=cb550+tank&_from=R40&rt=nc

[geoluv]

Nice 550F tanks can be difficult to come by. FYI - the '77-78 K models are basically the same tank and can be easier to find. However, the petcome is on the opposite side.
Start a thread in the parts wanted area, someone has got to have a spare.

I'll take any 500 or 550 tank the petcock style changed and the side it's on changed but the mounts all match right now I'm sorta desperate. 

[calj737]

Don’t weld a patch over the pinholes on the bottom, cut out the area and weld a new patch in instead. Then you won’t get leaking between the two surfaces which will turn to rot.

[Little_Phil]

Nice 550F tanks can be difficult to come by. FYI - the '77-78 K models are basically the same tank and can be easier to find. However, the petcome is on the opposite side.

I don't think so Stev-o. All 500/550 tanks have petcock on the LHS. Only difference 550Fs to 550K3 and 1978 (apart from paint finish) may be thread dia at petcock fitting.

[Stev-o]

Nice 550F tanks can be difficult to come by. FYI - the '77-78 K models are basically the same tank and can be easier to find. However, the petcome is on the opposite side.

I don't think so Stev-o. All 500/550 tanks have petcock on the LHS. Only difference 550Fs to 550K3 and 1978 (apart from paint finish) may be thread dia at petcock fitting.

That could be, Phil.  I do remember a slight differance with the pet cock!  Thanks

[geoluv]

That could be, Phil.  I do remember a slight differance with the pet cock!  Thanks

The difference is the 500s and the '74 550 have the petcock that attaches with two bolts and the 75 and 76 f models had 20x1.5mm petcock threading as did the 750f.  The rest are 16x1.5mm threading which is much more common in old Hondas.  Some 77s got the leftover tanks from 76 so if you have a 77f model you have to check to see if you have 20mm or 16mm petcock sizing.  (Mine's the proper 16mm)