Author Topic: Cb250k3 first restoration project  (Read 791 times)

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Cb250k3 first restoration project
« on: March 31, 2018, 05:58:50 PM »
Bought a CB250K3 which though Mot’d and running was a bit of a dog and showed it’s age. Mileage? Anyone’s guess as Mot s showed anything from 34,000 to 8,500 and back up 🤔. Visible problems, crappy paint, hand painted frames, dented and rusted chrome. Starter motor removed!

Rode home but pretty gutless,  checked compression down from 170psi to 90psi. Squirted some oil down the bores no change in compression so probably valves, last owner did say he had just done some work on the valves.

Any way now all stripped down and intend to do a complete restoration. wish me luck 😀
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline Bryanj

  • SOHC Jedi
  • Posts: 5453
    • View Profile
Re: Cb250k3 first restoration project
« Reply #1 on: March 31, 2018, 06:08:55 PM »
Back in the day was common for these to shatter rings if thrashed from cold, no matter how new or old they were

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #2 on: March 31, 2018, 06:23:43 PM »
better get ready to catch some bits when I take the barrels off then 😉
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline AshimotoK0

  • SOHC Jedi
  • Posts: 4992
  • Mad Scientist.... more power Igor ! ٩(̾๏̮̮̃̾๏̃̾)۶
    • View Profile
Re: Cb250k3 first restoration project
« Reply #3 on: April 01, 2018, 10:31:58 AM »
Biggest problem is cam/followers/end bearing ..notorious for pitting/scoring/wear. Getting harder and harder to find decent ones, even though around a million of that K model sold in various guises. Mainly down to lack of oil changing of course and the Americans seem worse than us for that, so even  low mile imports often have trashed top ends. At least your K3 is the 1st to have the '312' style rockers and the 'skinny' cam.... which are slightly easier to find.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline philward

  • SOHC Master
  • Posts: 1130
    • View Profile
Re: Cb250k3 first restoration project
« Reply #4 on: April 01, 2018, 04:38:48 PM »
Good luck with the build. I have a soft spot for the K3 as it was my first road bike - New in Sept 71. I had shattered ring thing that Bryan commented on.
Current Bikes:-
Kawasaki ZZR1100D3
Honda CB750K2
Honda CR750 Replica
Honda CB750K6 Cafe Racer Project
Kawasaki ZZR250 (1990)

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #5 on: April 01, 2018, 05:08:17 PM »
My intention is to get the cam and rockers re chromed and profiled as well as replace all bearings, rebore etc. Using this first restoration as a steep learning curve so hopefully my next one will be easier and hopefully cheaper 😉

But will probably be just as hard and expensive. 😀
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline AshimotoK0

  • SOHC Jedi
  • Posts: 4992
  • Mad Scientist.... more power Igor ! ٩(̾๏̮̮̃̾๏̃̾)۶
    • View Profile
Re: Cb250k3 first restoration project
« Reply #6 on: April 02, 2018, 07:57:07 AM »
My intention is to get the cam and rockers re chromed and profiled as well as replace all bearings, rebore etc. Using this first restoration as a steep learning curve so hopefully my next one will be easier and hopefully cheaper 😉

But will probably be just as hard and expensive. 😀

I think they Stellite weld and grind back to shape John..no plating involved. Probably cheaper to get a nice used  set from the States or  even DK if you are lucky...decent used are around ..just take some trawling on the internet. I put 25k miles on my K3  (plus the 10k it had on it when I got it) and the cam & rockers were near perfect but I changed the oil ! Don't forget to look at CL/CB350 .... same cam & followers.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #7 on: April 02, 2018, 05:54:49 PM »
Thanks Ash, I think I will be bothering you a lot in the next few months 😉
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline AshimotoK0

  • SOHC Jedi
  • Posts: 4992
  • Mad Scientist.... more power Igor ! ٩(̾๏̮̮̃̾๏̃̾)۶
    • View Profile
Re: Cb250k3 first restoration project
« Reply #8 on: April 02, 2018, 07:29:58 PM »
Thanks Ash, I think I will be bothering you a lot in the next few months 😉

No worries at all John .. glad to have another CB250/350K owner on board. If you need any advice/parts just shout.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Laverda120

  • SOHC Pro
  • Posts: 828
  • Honda 400/4 F2
    • View Profile
Re: Cb250k3 first restoration project
« Reply #9 on: April 07, 2018, 11:20:57 AM »
John, if you don't have any luck obtaining good s/h cam and followers Newman Cams can metal spray and reprofile your originals as they did for the cam and followers of my CB250RS. First class service as well.

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #10 on: April 07, 2018, 12:51:22 PM »
Thanks for that, I’ll get a better idea of what actually needs doing when I start in the engine properly
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #11 on: June 30, 2018, 11:10:52 PM »
Quick update, rolling chassis nearly done, then can start stripping down the engine 😉
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline Fenderfreak

  • SOHC Associate
  • Posts: 88
    • View Profile
Re: Cb250k3 first restoration project
« Reply #12 on: August 09, 2018, 09:34:41 AM »
Finally on its own two wheels
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline K2-K6

  • SOHC Master
  • Posts: 2117
    • View Profile
Re: Cb250k3 first restoration project
« Reply #13 on: August 09, 2018, 10:01:33 AM »
Looking very smart.

It's a nice getting over that threshold of a rolling bike and starts to feel like real progress.

Offline mickwinf

  • SOHC Master
  • Posts: 1076
    • View Profile
Re: Cb250k3 first restoration project
« Reply #14 on: August 09, 2018, 11:56:38 AM »
looking good, same colour as my k4 i had when i was 17, went to isle of man twice on it, but did have the piston problems mentioned.
Love the 500/4 and 550 own 2 at the moment.