Topic: 1975 CB 550K Fouling Plugs -- Please Help

[dmpventures]

Hello Honda forum! I am a newbie to Honda street bikes and their mechanical repair. I'm having some spark plug trouble with my amazing 1975 CB 550k and I'm hoping you can help me.

Since I bought the bike (3 months ago), I've fouled several sets of spark plugs. The plugs are always black and wet (I think oil). Additionally, pipe #1 puffs grey smoke when revved, while pipes 2, 3, & 4 puff a very small amount - almost unnoticeable. A family member thinks the issue might be caused by bad piston rings. Is this correct and what else might it be?

Just FYI, using my bike manual, I have completed the following on the bike (I'm not sure if any of these items might be related to the present issue):

1. oil change (and filter) - twice
2. cleaned gad tank
3. added a fuel stabilizer
4. cleaned carbs - rebuilt carb #1
5. new tires
6. cleaned rear brakes
7. cleaned chain
8. cleaned and lubed cables
9. synced carbs using a manometer
10. replaced tact cable
11. changed the pipes from stock (they were trashed  ) to drag pipes
12. repaired all known wiring problems

[calj737]

If it is indeed oil, then there are 2 possible cause, piston rings or valve seals.

When you first bought the bike, what condition were the plugs in? Was there evidence of smoking when revving the engine as you describe it now? If these symptoms arose after you rebuilt #1 carb, re synced, etc, then possibly you've got your adjustments out of whack and I'd think its gas, not oil on your plugs.

Have you been able to perform a compression test on the engine? That will help greatly in determine the health of the rings, or valve train. If you detect low numbers or "leaks" the only solution is removing the  head and perhaps the jugs.

You should check out Hondaman's book (forum member here) as it is a definitive bible for these bikes. Too numerous members have sworn by it and used it to become very knowledgeable wrenchers.

[Black 750K8]

Do you know if the bike has been sitting for a long period of time before you got it? If so not unheard of for rings to stick then brake loose after about 100 miles. Try some PB Blaster in each hole turn it over slow by hand to mix it up let sit overnight. Need a little more history on the bike. The old nose knows what do the plugs smell like as soon as you pull them and are they all hot? What type of air filter? 4. cleaned carbs - rebuilt carb #1 Tell us just how far did you breakdown the carbs and what size jets are in them now? What did you do to #1 that you did not do to the others and why?