« previous next »
Pages: [1]   Go Down

Author Topic: Bent valves?  (Read 1248 times)

0 Members and 1 Guest are viewing this topic.

Offline jacksonrpower

  • Full Member
  • *
  • Posts: 16
Bent valves?
« on: December 01, 2013, 10:49:27 AM »
I was installing my cylinder head cover and I had rubber bands over the tappets. I adjusted all the tappets and everything seemed fine but when I rotated the engine I heard a loud pinging noise coming from the valves. Have I bent the valves? I don't understand what I did wrong.
Logged

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Bent valves?
« Reply #1 on: December 01, 2013, 11:58:36 AM »
The rubber bands aren't a cure all, only an aid.  Still need to back out all the adjusters and be careful.
The shop manual warns about this...
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 jacksonrpower

  • Full Member
  • *
  • Posts: 16
Re: Bent valves?
« Reply #2 on: December 01, 2013, 12:29:34 PM »
So what causes the valves to bend?
Logged

Offline MoMo

  • Really Old Timer ...
  • *******
  • Posts: 8,275
  • Ride like you're invisible
Re: Bent valves?
« Reply #3 on: December 01, 2013, 12:35:37 PM »
If the rocker was not centered over the valve(as shown in the image) you would have adjusted the clearance wrong forcing the valve down too far and subsequently hitting the piston top. Did you only have  the top cover off or was the cam off also?
Logged

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: Bent valves?
« Reply #4 on: December 01, 2013, 01:02:49 PM »
If the springs were off..did you bonk them after assembly.?
 Maybe. A keeper seating..small chance..
Logged
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline jacksonrpower

  • Full Member
  • *
  • Posts: 16
Re: Bent valves?
« Reply #5 on: December 01, 2013, 01:09:58 PM »
I only had the top cover off. I just bought this motor off craigslist so it could have been like this already.
Logged

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Bent valves?
« Reply #6 on: December 01, 2013, 02:21:04 PM »
Quote from: jacksonrpower on December 01, 2013, 12:29:34 PM
So what causes the valves to bend?
When the cover is tightened down and the valve adjuster is not on the top of the valve stem, the downward movement bends the valve stem.
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 jacksonrpower

  • Full Member
  • *
  • Posts: 16
Re: Bent valves?
« Reply #7 on: December 01, 2013, 05:09:46 PM »
So will I just need new valves in my head? or are my rocker arms damaged too? I have a head from a cb500 laying around.
Logged

Offline TwoTired

  • Really Old Timer ...
  • *******
  • Posts: 21,805
Re: Bent valves?
« Reply #8 on: December 01, 2013, 05:45:39 PM »
Quote from: jacksonrpower on December 01, 2013, 05:09:46 PM
So will I just need new valves in my head? or are my rocker arms damaged too? I have a head from a cb500 laying around.

New valves and maybe valve guides if they were distorted..

Probably better off using the head from the 500.
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.
Pages: [1]   Go Up
« previous next »