Honda CB750 Sandcast

New member introduction

jjb · 10 · 10175

jjb

  • Newbie
  • *
    • Posts: 5
    • View Profile
    • Big Stick Racing
Hi - I just found this forum and am starting the process of restoring a kind of unique 750. It's gone through a series of friends dating back to the early '70's when a guy named Dick Varner owned it. Evidently, Dick was an employee of Yoshimura and built this bike from some of their race parts.

Anyway, here are a couple of photos of the numbers .. I have some internal engine and external bike photos to post later. I'm hoping you guys in the know might be able to help me with some history on this bike. I personally know where it's been since about 1977.

Here's the frame number


.. and the engine case numbers .. (sorry about the leaf ..)
« Last Edit: October 31, 2010, 11:52:42 am by jjb »


Joe K

  • Sr. Member
  • ****
    • Posts: 268
    • View Profile
Hello Jim,

Sounds like you got a really nice piece of history, with Dick Varner and Yoshimura. I see that the engine was originally unstamped. Is the engine case sandcast or diecast. You will know by counting the number of screws on the clutch cover. 9 is sandcast, 10 is diecast. Either way, the history makes all of it.

Joe


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
Hello Jim Brewer #90 !

What you have looks like a nice piece of Yoshimura racing performance history.

Gotta love those CR engine numbers !

Your 6148 frame number is a sandcast vin.

Your crankcase vin pad appears consistent with the diecast type as does the smooth surface of what i can see of the crankcase.

Follow Joe's advice to identify crankcase type, count the screws fixing cl.cover to crankcase.

BTW, this is Steve Swan, Dad of Corbin - MRA #900, 2003-06

Did not know you live in Ft. Collins......? !

I live in Ft. Collins ! Call me anytime ! 443.2432

PS - To learn more about the history of your bike, try contacting Mark McGrew of M3 Racing he builds CR's machines and CB75o engines - http://www.m3racing.com/


jjb

  • Newbie
  • *
    • Posts: 5
    • View Profile
    • Big Stick Racing
Hey Steve - tell Corbin I say "hi". Tell him to get his butt to the new track else I'll call him a backmarker!

Jan 2, 2010, 9:29am, Steve Swan wrote:
Follow Joe's advice to identify crankcase type, count the screws fixing cl.cover to crankcase.
 
 

Joe, thanks for the hint, and Steve, you called it. It has 10 screws, so these are diecast cases. (do I get kicked off this board, now? )  ??? ???

Thanks for the m3racing reference! I'll see if he can identify anything in the photos. (that I'll post next) I'll give you a shout soon.


jjb

  • Newbie
  • *
    • Posts: 5
    • View Profile
    • Big Stick Racing
Ok, I found some photos that I took almost 19 years ago when I picked up the bike from my friend Woody (in the photo). Woody's the taller guy, I'm the shorter one. Woody bought the bike from our mutual friend Jeff Moo, who in turn had bought the bike from Dick Varner. (Jeff and Dick were high school classmates & riding buddies back in the 70's).



and here's the bike naked ...



jjb

  • Newbie
  • *
    • Posts: 5
    • View Profile
    • Big Stick Racing
A friend (Mick Jones) went through the motor in 1992 to see what kind of condition it was in. Here are some pictures of the insides ..

First the upper case & crank .. it had an RC engineering clutch in it with bronze plates ..



The crank looked like it had some work on it. The counterweights were polished and rounded. It has 835cc Yosh pistons and aluminum Yosh superrods.







« Last Edit: October 31, 2010, 11:53:50 am by jjb »


jjb

  • Newbie
  • *
    • Posts: 5
    • View Profile
    • Big Stick Racing
The head was also pretty interesting .. I know it has a pretty hefty cam since when I heard it running, it would barely idle and had quite a lope when it did.

Here are some shots of the head. It seems someone spent some time on the ports by teardropping the guide areas ..

Intake ...



Exhaust



Combustion chamber ..



I'd be curious as to how modified this motor looks to you guys. Honestly, it's the first and only CB750 I've seen inside so I don't know how typical some of this stuff is.


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
Hi Jim !

The requirement for membership is to own a sandcast engine, appropriate vin frame or both.

You have a sandcast vin frame so you are in !

Corbin got married and ran off to Oregon a couple years ago, none the less i will tell him you say hi !

There are other members who can tall specifically what's been done to your engine. I do know there was un-necessary metal in the guide area, in fact i am having my head cleaned up on my unstamped sandcast engine. Am told just that simple clean up in the guide area will give 7-8 additonal hp. Tom Wirth is building that unstamped set of sandcast cases into an engine for me, planning it will be finished and i will pick it up at the end of this month !

I know the CR750 factory kit was major package including not only engine parts but also chassis and body sprung and unsprung parts. This kit gave the engine 90 hp at 10,500 rpm and being the single cam was long and small diameter, shaft whip was a problem.

I have heard private eng.builders would build up heavier cam towers and then use larger diameter bolts going through holes milled through the top of a beefed up cam cover, all in the effort to achieve more rigidity and minimize cam shaft whip.

The exhaust in your pics appear obviously early (rare) Yosh ! The brakes and forks look like modified stock parts or perhaps some pieces are from a factory CR kit.... Is there a brand name on the wheels ?

I am very certain Mark McGrew can tell by looking at the pics exactly what you have and i suspect you don't have a run of the mill period cafe, considering the Yosh connection !

The crank and rods are beautiful !

One could suspect with the "CR" stamped into vin pad, the engine was built to CR specs.........

Love that Yosh decal on the oil tank !

When are you planning on having the project finished ?

You've got a sandcast frame with some very rare racing parts making one very cool race kitted CB750 !

Keep us posted !


fang

  • Newbie
  • *
    • Posts: 22
    • View Profile
    • Food Renegade
Hi Jim. 
You have a fantastic bit of CB750 awesomeness there.  It is not 'factory CR,' but that does not mean it is not fantastic.  It looks like one of the rare true Yoshi racer 'CR750' builds.  His were not really based on the Honda CR kit, rather he kitted his own (often better) parts to build a track racer.  I believe his bikes were better, and possibly just as collectible.  Those incredible hand bent pipes, the rear disc brake, tank, etc -- all rare race bits, but not Honda factory. 

For whatever it is worth, here is a good pic of a factory CR750:


CYCLE magazine Oct 1970.  I had a digital copy of the whole CR750 article somewhere, but I recently had a harddrive crash, and might have lost it then.  If I find it I will post it here for you.  Or if you wish, those magazines pop up on eBay once in a blue moon.

Good luck with your bike build. 

peace and grease,
-steve


fang

  • Newbie
  • *
    • Posts: 22
    • View Profile
    • Food Renegade