« previous next »
Pages: [1]   Go Down

Author Topic: Honda CB 500 four cylinder 4 spark plug turning black  (Read 486 times)

0 Members and 1 Guest are viewing this topic.

Offline Whosrody

  • Full Member
  • *
  • Posts: 1
Honda CB 500 four cylinder 4 spark plug turning black
« on: August 30, 2021, 03:25:50 AM »
Hello
I have a problem that my number 4 cylinder spark plug is turning black and I dont know if its the carb or oil ring. I rebuilt the cylinder head with new valve seals and so on. I have cleaned the carb also and still no hope. Maybe theres a way to unstuck the oil ring without taking apart anything? I made a mistake that I did not take the cylinder off when I rebuilt the head  :(
Logged

Offline jaytee-nz

  • Hot Shot
  • ***
  • Posts: 655
Re: Honda CB 500 four cylinder 4 spark plug turning black
« Reply #1 on: August 30, 2021, 03:58:13 PM »
Is the spark plug black with oil / wet looking, or is it black with dry soot ? Oil would indicate that's the cylinder is burning oil while a sooty deposit would indicate a carb issue e.g. float level is too high.
Logged

Offline newday777

  • Really Old Timer ...
  • *******
  • Posts: 5,565
  • Avatar is my 76 K6 in Colorado w/Cody on back 1980
Re: Honda CB 500 four cylinder 4 spark plug turning black
« Reply #2 on: August 30, 2021, 04:17:24 PM »
Quote from: Whosrody on August 30, 2021, 03:25:50 AM
Hello
I have a problem that my number 4 cylinder spark plug is turning black and I dont know if its the carb or oil ring. I rebuilt the cylinder head with new valve seals and so on. I have cleaned the carb also and still no hope. Maybe theres a way to unstuck the oil ring without taking apart anything? I made a mistake that I did not take the cylinder off when I rebuilt the head  :(

Welcome aboard Whosrody
What process did you clean your carbs by?
Ultrasonic? Deep soak? Or spray? Or?????
I take it your bike sat unused before you did the head work and carbs??

Logged
Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Honda CB 500 four cylinder 4 spark plug turning black
« Reply #3 on: August 30, 2021, 05:04:54 PM »
Black oily or dry black powdery?  The latter is a too rich mixture, and should wipe off easily.  The former will coat your fingers with greasy black smudges.

Cheers,
Logged
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline dave500

  • Really Old Timer ...
  • *******
  • Posts: 17,051
  • WHAT?no gravy?
Re: Honda CB 500 four cylinder 4 spark plug turning black
« Reply #4 on: August 30, 2021, 11:33:37 PM »
also check the plug caps resistance.
Logged
Pages: [1]   Go Up
« previous next »