Topic: CB550F rough at lower RPMs

[Rmak98]

I've been going over posts and replies for a month or so now. I am still at a loss of what to try next. Long story but, was given this 76 550F from a relative, driven 11 years , sat for 35 in his garage. So I when I got it to fire up and run in my garage, I thought I'd go a little deeper, go through it to make it a good running machine. Odd, but seemed to run better till about 2 months ago.
Starts easy and will idle fine, but up from there is the problem.

Runs rough from Idle to about 3500 RPM, missis real bad, chugs , seems to clear up while accelerating, but if level throttle below 3500, misses, backfires,  then when I level out above 4000 seems to be OK.

Rebuilt carbs twice now, new coils, plug caps, several sets of plugs, had a lose rocker shaft, so after some checking, found out that the 77 rocker cover went to long shafts and was an upgrade, so found one on line, new battery, points, condensers, advance working, new manifold orings, new rubber couplers from carbs, install new air filter, the housing,  air box, clamps, couplers are oem, muffler rusted out, installed Delkevek 4 into 1. Top end rebuild, pistons, rings, gaskets, ring end gap was .007, so I didnt consider oversize, honed cyl walls, good cross hatch. lapped valves, compression is seems low, but 120 to 125, when I add a little oil, adds about 3 to 5 psi to each. good spark on all plugs, adjusted valves, set point gap, 013, plugs .028, timed static and with light checked and checked.

Some of the things I've read to check from some of your posts.
    Battery at 12.56v,( 11.73v at points 2/3),( 11.20v at points 1/4).( 12.28v yellow to Black White wire, 5.1 ohms), (12.29v blue to black white wire 5.2 ohms). 1/4 plug wire to plug wire 15.52 k ohms 2/3 plug wires 15.06 k ohms. plug cap resistance  #1-4.62 ohms,#2 4.72, #3 5.20 #4 4.72.
Spark plugs are dry sooty, Air mixture screw from 1 turn out to 2  to 2 1/2 turns out. can't tell much difference.

Is my compression too low, causing the problem. the soot makes me think it's too rich.
Installed smaller jets from Jets r Us. and Common Motor,  main jet from 98 to  80, pilot jet from 38 to 35. Cant see that it has helped. Carb needle clip setting is second from the top, so I could raise the clip one to lower the needle, but from what I read here, that comes into effect at the higher RPM"s.

Thanks for putting up with this long post, but if anyone has anything I can check , I'm all ears
I've gained so much reading the posts and replies, thank to all who take the time to contribute.

[calj737]

Main jet at 80 is too small.
Have you checked the emulsion tubes? Are they perfectly clean? Like surgically clean? That would explain the low RPM chugging.

Something to also check (not mentioned) is the fuel level in the bowls. The Clear tube method works best to confirm what is actually happening. Since the carbs have been off a few times, I think it’s worth investigating.

[Rmak98]

I replaced the emulsion tubes with the new ones that came in the kit, I'll check that nothing is clogging them up. . I'll check the fluid level with the method you show. I still have the 98 mains I removed. May try going back. Is the 2nd clip position correct ?

[calj737]

98 should be correct. Although, if you used non- Keihin brand jets and needles, the stock configurations are moot as there are subtle but meaningful differences in the brands.

Turn your air screws back in to stock settings too. Your situation of dry, sooty plugs sounds more like an ignition problem and fuel level issue. One thing at a time though… Carbs first.

[bryanj]

Replacement emulsions could be the problem, kit brass is known to be inaccurate, if you still have the original brass ultrasonic and refit

[newday777]

I replaced the emulsion tubes with the new ones that came in the kit, I'll check that nothing is clogging them up. . I'll check the fluid level with the method you show. I still have the 98 mains I removed. May try going back. Is the 2nd clip position correct ?

As You have said, "I replaced the emulsion tubes with the new ones that came in the kit"
1. What kit did you use?

As bryanj mentioned that aftermarket kit brass very often has incompatible and inferior brass parts to the stock Keihin brass that came in the carbs and is very cleanable to reuse.
2. Did you mix old needles to the new emulsion tubes you put in? If so, that might be the problem as the kit emulsion tubes are most likely tapered different from the original and won't match the needles. Again, I agree that cleaning the original brass parts is the far better chances for better running. That is the 1st steps to go through to try and correct it. Reply back here with your results after.
Did you click on the notify button to get notification of replies to this thread? It's not done automatically on this forum unfortunately....... :'(

3. You said that you did points and condensers. Did you get new points and condensers from Honda or aftermarket? If aftermarket Chinese, the condensers nay have failed already (very common). Important to get new from Honda only to get TEC brand if possible.

I have just gone back through your posts from when you joined last year trying to get all your info you have posted about what you've done so far and your replies to questions ask/information/suggestions given you to try to decipher anything missed. You've done a fairly decent job of getting the bike back up and running. Have you had it out and running well out on the road for many miles? The 550 is a great bike. I bought a new 77 K model for my 1st wife and I would ride it occasionally to work at the shop. I didn't do any of the work on it myself as it was new still and it didn't need anything other than oil changes and tune ups.

[dave500]

have you set and checked the ignition with a decent timing light?and also set the points via dwell not gap?also use your timing light to check the advance curve,you must have the ignition squared away first perfectly before you toy with random jet changes.

[Rmak98]

Thanks all for the help, you've given me some direction.  First, neither the carb rebuild kit or the points/condenser are OEM. I should of known when the pilot jet in the kit was about  3/16" shorter than the one I removed, so installed the old one. I have a timing light and did make sure the advance was working.
So I'm going to purchase Keihin kits and Honda points/condenser, then clear tube level check, I also have a 4 gauge vacuum sync kit (Amazon) not sure how accurate.
Thanks again, As always you guys are a huge help. I need to realize these bikes need to be set up correct to give many miles of riding. I was thinking, its a Honda, get everything close, it'll run forever.

[Rmak98]

Got my Dwell meter out today, I rechecked point gap and timing. points @012 dwell at 24 to 24.5 reading on the 8 cyl scale, timed static and with light. I run out of room on the 2-3 points to get the proper timing - just a degree short of being advanced correctly, I'm firing just after the F.

Will rebuild carbs after getting a correct kit, and replace points, and condenser.

Here's a pic of the plugs after  setting everything this morning and a 40 min ride on backroads, no idling, shut off , coasting into the driveway. All dry soot.

My local dealer does not have or able to order Honda points and condenser, or Keihin carb kits. Can someone suggest a dealer or aftermarket parts that are correct/trustworthy. 

Thanks again for the help.

[calj737]

https://jetsrus.com/a_jet_kit_street/honda_550_CB550F_1976.html

[newday777]

Just get the whole points plate assembly.
#1 $72 you save $28 and get the whole assembly.

At $25 each for 2 points and 2 condensers,  that's $100.

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550FA_(76)_SUPER_SPORT_550_FOUR%2c_JPN%2c_VIN%23_CB550F-2000003_TO_CB550F-2010866/POINTS_%2b_ADVANCER/b3284679-ab4c-427a-8b68-959c823bd603/bab216c2-171b-4b66-835d-a332f5affb07/y

[Rmak98]

Thanks guys, makes sense getting the plate assembly, I'll get the correct jets coming also.
My needle clip is set at the 2nd from top, should I leave it there for now, that's where it was when I went into it the first time.

I'll let you know how it goes after the new parts are installed.

Thanks again

[calj737]

Yes, as long as they’re stock needles.