Topic: 1977 CB550K carb issue

[Maverick88]

Picked up a 1977 CB500k that is completely stock from what I can tell other then the carbs. The PO resurrected the bike with a new engine from the same year and put in 022a carbs off of an earlier year. Overall the bike is in decent shape and runs but I am finding the PO installed quite a few parts wrong.... Brake piston backwards, rear wheel spacer in the wrong spot causing it to bind with any amount of torque on the axle nut. Since he did quite a bit of work on the bike I am now going over everything to make sure its installed correctly, not missing parts and is safe to ride.

I have pulled the rocker cover do deal with an oil leak and stripped screws. Did the valve adjustment, timing chain and ignition timing. I am now at the carbs and the immediate issue I'm noticing is that they do not have a vacuum port on them as that year had them on the engine intake manifold. What are my options here? Can I drill and tap some ports into my existing manifolds. Find some manifolds that have the vacuum ports assuming they will fit or am I better off tracking down different carbs? I want to come up with a plan before I begin ordering parts to rebuild the carbs.

[dave500]

i was gonna ask that about the vacuum ports if you hadnt noticed it,drilling and tapping is doable,see if you can locate the correct intakes first,those earlier carbs are the better ones to have.

[newday777]

Welcome aboard the forum Maverick88
I don't know if you can drill and tap in the intake manifolds or not, do yours have a bung area where the holes should be?
But.... the good news for you on this.... I looked up the part numbers and David Silver Spares in PA and in the UK(they buy up NOS part lots) have both of the earlier intake maifolds for the CB500 and CB550(1971-1976) available for $35(USD) ea that have the boss on the bungs already tapped for the screws. #7- 12241-323-000 & #8- 12242-323-000  links below (you'll also need to get the 4 sealing washers and screws, and 4 intake orings)

https://www.davidsilverspares.com/parts/by-part-number/partnumber_1683/

https://www.davidsilverspares.com/parts/by-part-number/partnumber_1689/

Be sure to replace the 4 orings that seal the intakes to the head even if you do end up drilling and tapping your intakes.

#38 (4 orings) 91302-001-020 $2.33 at South Sound Honda in Washington, usually the best price online for parts still available from Honda(David Silver has them at $3.82/ea)
https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CYLINDER_%2b_HEAD/f77665b3-598c-4e35-ad4b-7a873770e3e5/21bfe9b8-9439-4800-a477-fd60414d4eec/y

Sealing washers 5mm #31 (4) 90452-323-000

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CYLINDER_%2b_HEAD/f77665b3-598c-4e35-ad4b-7a873770e3e5/21bfe9b8-9439-4800-a477-fd60414d4eec/y

Pan screws 5mmx6mm #46 (4) 93500-05006-0A

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CYLINDER_%2b_HEAD/f77665b3-598c-4e35-ad4b-7a873770e3e5/21bfe9b8-9439-4800-a477-fd60414d4eec/y

BTW
Go to the new members section and introduce yourself and your bike. ( Pictures are always good of your bike.)
And there's is a Project Shop section where you can start a thread topic on your bike, keeping your work on it all in one place.

New members introduction
http://forums.sohc4.net/index.php/board,58.0.html

Project Shop

http://forums.sohc4.net/index.php/board,103.0.html


(I was a parts manager back in the 70s and still know how to use the parts fiches.)

EDIT....
I just looked at your profile and see you are in Alberta so to get better shipping costs you might try your local Honda shop for the orings, screws and washers and check with David Silver Spares in the UK as their shipping to you from the UK might be better than through the Pennsylvania warehouse on the manifolds???

[calj737]

You most certainly can drill and tap those intakes. No bung needed.

[RAFster122s]

You want to file the heads of the screws flush with the intake tract…you will have better carb performance that way…

[Maverick88]

Thanks for the advice everyone. I ended up tapping some ports into the intake since I have a second seized engine sitting around for parts.

You went above and beyond Newday, thank you! I plan on tearing into the engine a little more this winter and will make sure I replace the intake o rings when I rebuild the top end to fix the minor oil leak.
I'll hit up the new member introduction and start a project thread for my bike.

[newday777]

That's great you can drill and tap the holes in. Have fun working on it. And riding it!

[Maverick88]

So I replaced the original 4into4 exhaust  that was rusted out with a Delkevic 4into1.

With the original exhaust the bike would start up no problem and ran, but its idle speed would bounce all over the place. Pretty sure I had some vacuum leaks that contributed to the rough idle, have since fixed them. With the Delkevic It will start just fine but will bog down unless I keep the RPM's at 2000, can rip around the block but then it will die and only run if I close the choke.

Fiddle with the needle position or just bump up the Jet size?

1977 CB550k (stock except for the exhaust and earlier carbs)
air box intact
Delkevic 4into1 straight muffler

022a Carbs
Main 100
Slow 38
Needle clip in the 4th position
Air screw 1 1/2
Bench sync done

I'm completely new to carbureted bikes and haven't quite wrapped my head around the tuning process. What I've gathered from the threads is don't play with the needle potions and bump up the main jets a size and ideally only uses original Keihin parts.

I've been ordering all my parts from 4into1 and purchased the Carburetor rebuild kit originally and was going to purchase the replica jets that they sell since they don't carry the OEM. They have good reviews on the replicas, should I really worry about it? Recommendations on what sizes to purchase so I have enough options to get it working? I'm getting tired of ordering parts constantly.

[calj737]

There’s nothing wrong with your stock jets, so don’t waste your time/money.

Since you solved the vacuum leaks, it would be good to get the bike warmed up, then vacuum sync the carbs on the bike. Set the idle to 1200+/-. Once synched, you should no longer need to worry about revving to keep the motor alive, and only use choke to start the bike, reduce to 1/2-1/4 and take off. Open the choke completely promptly. These bikes don’t need choke to run.

You might also double check your fuel level in the carbs via the Clear tube method to confirm you have adequate but not excessive fuel levels.