Author Topic: 750K3 engine sleeving  (Read 1123 times)

0 Members and 1 Guest are viewing this topic.

Offline RedDawn

  • Full Member
  • *
  • Posts: 9
750K3 engine sleeving
« on: April 27, 2010, 09:13:19 AM »
Over the weekend I opened up a 750K3 engine that had been burning oil, and discovered that the bottom of my sleeves (the ~1/2" bit that extends down beyond the fins) are damaged. One cylinder has a 3/8"Hx1/2"W chunk missing, and another cylinder has a rough edge from a few chips (1/8" or so) taken out. The engine was bored out to 836.

The motor is from a bike that was given to me after it sat in someone's yard for a decade. I assume that the cylinders will need resleeving to be used again? The damage does not extend up into the cylinders, it is just in the bottom bit on two of the cylinders. There is some scarring on the walls of all four cylinders so a honing will definitely be necessary, maybe even boring further. I found Wiseco stock sleeves for $96 / cylinder (part H15SL), but how much does it usually cost to have a machine shop install new sleeves? Is it something that I can do myself with a press?

Say I went with CycleX's 850 kit, I'd be looking at $400 for sleeves, $250 for pistons, plus sleeve installation, plus boring. I came across this: http://cgi.ebay.com/ebaymotors/NOS-Honda-CB750-900cc-Racing-Big-Bore-Piston-Kit-CB-750-_W0QQcmdZViewItemQQhashZitem45f2723e2fQQitemZ300420316719QQptZMotorcyclesQ5fPartsQ5fAccessories which would be a bit less expensive at first, but I don't know whether I'd be able to get rings down the line for it or where I'd go from there. Any thoughts?

Am I better off just finding a replacement set of jugs?

I currently do not have pictures of the damage, I'll try to take some tonight and post them tomorrow.
'73 CB750, '73 CB350 twin

Offline MRieck

  • Really Old Timer ...
  • *******
  • Posts: 10,565
  • Big ideas....
Re: 750K3 engine sleeving
« Reply #1 on: April 27, 2010, 09:25:55 AM »
Get another cylinder and start fresh.
Owner of the "Million Dollar CB"

Offline MCRider

  • Such is the life of a
  • Really Old Timer ...
  • *******
  • Posts: 14,376
  • Today's Lesson: One good turn deserves another.
Re: 750K3 engine sleeving
« Reply #2 on: April 27, 2010, 09:29:44 AM »
Get another cylinder and start fresh.
Wow, great point.  I for one was completely stuck on his resleeving.

But a good used stock cylinder can be had often for less than $100 then bore to 836 or whatever and go.
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: 750K3 engine sleeving
« Reply #3 on: April 27, 2010, 09:43:30 AM »
If its got wear, you get another cylinder, new rings, bore to proper clearance..= like new..
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 RedDawn

  • Full Member
  • *
  • Posts: 9
Re: 750K3 engine sleeving
« Reply #4 on: April 27, 2010, 12:06:57 PM »
Thanks a lot guys. I spent a long time this morning searching for things like 'cb750 jugs' 'cb750 sleeves', but never cylinders (seems obvious in retrospect). Came across a few fairly clean looking sets on eBay for cheap, went ahead and bid. I see a few with 'Buy it Now's for well under a hundred. Much cheaper than sleeving or any of the cylinders I found on eBay under my alternate search terms (couldn't find any for less than $200 before).
'73 CB750, '73 CB350 twin

Offline 754

  • Really Old Timer ...
  • *******
  • Posts: 29,058
Re: 750K3 engine sleeving
« Reply #5 on: April 27, 2010, 07:35:22 PM »
754Tip;
 Bid on cruddy ones, then swap sleeves.. cheap like borscht... ;D
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