Topic: 750 K0 honda Sandcast lower case, Diecast upper???

[wdammit75]

I'm the guy i the post " best 100 bucks a guy could spend". I was looking at the bike again today (K0 750) and there is a distinct difference in the finish and surface between my upper and lower case halves. The upper is clearly diecast, very smooth and no number stamped. The bottom, on the other hand is quite rough in finish. Is it even possible to have them bolted together?
  I do have pictures and will post them as sonn as I get home.  If it helps, my clutch cover is held on by 10 screws. My oil pan has 10 bolts as well. Maybe by some of those details someone could tell me if it's even possible.

Looking at the motor, the top case is the only thing out of place, color and surface wise.

 Can someone please let me know what you think/know?

Thank you

[CycleRanger]

More pictures would us make better guesses. 

[Magpie]

I have a sandcast motor and the clutch cover has 9 screws holding it on. My later motors, K0 and K1) have 10. The one just below where the clutch cable goes into it is missing on the sandcast ones. Sounds like an interesting life for that motor.
Cliff.

[wdammit75]

Wish it was closer. This is a pic from my last post.

[wdammit75]

Another

[Simpson]

Sounds like a sandcast that had the case broke by a drive chain. I would think a dealer replaced the upper side with a diecast.

[Don R]

I think I saw one a couple weeks ago. The owner mentioned it and I didn't realize what he was talking about until I read this. Is yours a high serial number sandcast? Like 10065xx or higher? He has known his bike since new and it has never been apart. It has all the clutch bolts too.

[Terry in Australia]

Well it's the lower sandcast case that has one less clutch cover screw, so no, your lower case is die cast. Typically, the lower case is a "rougher" casting than the top case, because you don't see much of it.

If you've got unstamped cases, (and presuming your K0 is an early sandcast build) your engine was probably a victim of a busted drive chain smashing your cases, this was pretty common with early K0's. Cheers, Terry.    

[wdammit75]

Well heres some more pics, maybe I was just being wishful!!!

[wdammit75]

1

[Terry in Australia]

Yep, my diecast K0 bottom case looks pretty much like that one. Cheers, Terry.

[bryanj]

You could/can not buy a new half case and no dealer who wanted to stay in business would fit just one half due to machining tolerances

[754]

IIRC my 10,XXX cases have batch numbers at the rear.. sorta where the carb hoses hang down.

 If you are taking the swingarm off for any reason, you could look.

[MCRider]

You could/can not buy a new half case and no dealer who wanted to stay in business would fit just one half due to machining tolerances

that's what i was thinking. The line bore for the crankshaft bearings has to be dead on and matched, case to case.

[754]

That is  true, but even on here I have heard of mismatched cases several times...

 Did the guy say the case was dealer installed, or did he get it done by a "mechanic" ? If that happened and was a mismatch, but turned over ok, it may go 5K or 50 K. If the owner was aware there was case problems, and started worrying about it.. he may have stopped riding it (cause he did not trust it).. and then sold it cheap..

 At any rate you wont know till you find batch numbers or measure the cases..... so if it runs, use it..

 And keep an eye out for early diecast cases.

[wdammit75]

I have spooken with the only owners before me, including the one who bought it new. They both said the bike was never returned to the dealership for anything. This is the way the bike came, period. The reaqson the guy parked it was that his brother-in-law was killed in a motorcycle crash shortly after he bought it. His wife DIDN'T want him riding anymore.

So what am I looking for in the way of batch numbers??? What about measuring the cases, from where to where? What are the specs for diecast vs. sandcast?  Any help??

[Terry in Australia]

That's interesting, but I doubt that a bike with no engine numbers made it out of the factory, got past a dealer, and escaped the notice of the DMV. When did the original owner buy it?

I bought my "new" 1975 CB750F in March 1978, it was still sitting in the crate, the F/F1 was a particularly unattractive bike and the dealers here couldn't move them, so I bought it at a heavily discounted price.

Maybe your K0 was a "shop bike" ("Demonstration Vehicle") that busted the original stamped cases very early in it's life, and was repaired with unstamped cases before the original owner purchased it? Cheers, Terry.

[754]

Those are probably day , and month , and maybe year numbers..common on diecast parts.

 If you pulled the swingarm, and looked at the split of the cases.. (my early diecast has these, cant say I noticed them on later cases) there may be a number above and below the split.. this will mean they were machined together and are matched cases.
 To actually measure the bearing bores, you would be measuring in ten thousanths of an inch, unless it was real bad (probably would not live long)

BTW there is at least one difference between early diecast and say 72s.... if you want to be correct..