Honda CB750 Sandcast

New Guy in OC needs suggestions - Just got bike 778

Gutz · 36 · 9741

Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
yes, long choke arm, a lovely desirable part.

2 hole airbox with no cracks, another rare part.

that think lip alternator cover, practically impossible to find if the bike does not come with one, i had to buy a motorcycle to get a thin lip cover.

fins on that smooth oil cover are a buzz kill.  unmolested, rarely available and spendy when one shows up, usually $500 - $600 spendy.  if it were mine, i'd do everything i could to bring that cover back to original appearance, but before you do, check inside to make sure there is not crack from over-tightening around circumference of bolt hole.

flip the tank over and post a picture or else go in to the website and you see lots of pics what a 19 L looks like on underside.

post a pic of the speedo and tach drives where the ferrules attach to drive.



Gutz

  • Newbie
  • *
    • Posts: 9
    • View Profile
Here's a couple more.







I have the original grip but it has some glue on it.  I'm curious about the controls. This side is brownish and I have the accompanying blinker control. Take a look.


There is a black one installed and an extra brown one we found. Was the black original?


How can I tell if this chain is still good? He replace the original with a "SuperChain".


Sgt.Pinback

  • Hero Member
  • *****
    • Posts: 695
    • View Profile
That's a great basis. As far as I can see very original. There are a lot of hard to find genuine early sandcast parts.

You will have to make a decision:  keeping it as it is with all the patina and just bring her back to the road or going the long way with a full restoration. That's what I do actually.

Before starting I would recommend to read through the restoration threads to get an idea.

That "brown" one is just faded. Lovely patina....
« Last Edit: November 01, 2016, 04:32:28 pm by Sgt.Pinback »
Cheers, Uli (Leonberg, Germany)


Gutz

  • Newbie
  • *
    • Posts: 9
    • View Profile
Got the carbs off and took a quick look. Seem pretty darn clean for sitting for 23 yrs. That being said, the other 3 bowls are seriously stuck on there! I tapped with a rubber mallet but I didn't have time to get any further and don't want to rush it. Any tips for getting those off and recommendations for cleaning? I was planning on a short simple green bath followed by carb cleaner.



Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
use a heat gun or a hair dryer to warm up the bowls, if you cannot then remove them with your hand, heat the bowl again and gently tap  the 3 walls of the bowl with a small dead blow mallet or a rubber covered handle of a large screwdriver.  they will come off, one at at time.  the same can be accomplished on stuck slides.  the 1', 2' and 3' fuel passageways will all need to be cleaned, ultrasonic is the best way to get them clear, then use wd40 and compressed air to test passageway patency.  be sure to remove the needle jet, pn 16133-300-004 from the carb body.  make sure all the orifices of 16139-300-004 and 99124-300-0400 are perfectly clear.  check the float needle for a wear ring.  i replace the worn needles with a Viton tip needle available from K&L supply.  i clean the float needle seat seat using a dremel tool and an industrial Q tip dipped in Simichrome, then after i have assembled rebuilt carb rack, i bench test the carbs for fuel leakage past the float needle valves.  if the float valves leak and the passageways and orifices are not clear, the carbs will not ever carburate correctly.

your bike so far has all the early parts one would expect to see on an 7xx vin.  if you search the forum using key words you can learn much about the distinctions seen on parts specific to your machine.  in the past month there was an excellent thread on the 3 tank types and date codes one can  expect to see on the tank as well as there are also other threads on dates codes seen on other parts.

Follow Uli's advice to restore or not to restore.  i would say the majority of us are all about restoring.  my suggestion to you, having an earlier production vin, is make 7xx a long term restoration project.  7xx is a solid basis for restoration.

if you don't have a 1969 factory parts book, buy a copy off ebay or perhaps you can download a copy of sohc4.net forum.

other handy tools are a #2 and #3 Vessel Megadora JIS screwdrivers, you can buy them on ebay for around $12 apiece.


kp

  • Administrator
  • Hero Member
  • *****
    • Posts: 1806
    • View Profile
Hey! Did anyone spot the pointer on the kill switch with no "on" "off" "on". That's 3 switches I've now seen on bikes in this Frame # range and being saying it for a number of years. For me this does ice the cake so I'm going to claim this as another distinction on Sandcast bikes. Yee Har. 🤓
Yabba Dabba KP


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
Hey! Did anyone spot the pointer on the kill switch with no "on" "off" "on". That's 3 switches I've now seen on bikes in this Frame # range and being saying it for a number of years. For me this does ice the cake so I'm going to claim this as another distinction on Sandcast bikes. Yee Har. 🤓

KP, what vin range do you suggest for a pointer type switch with  no on-off-on markings and i will update the 88 distinctions thread.  GREAT CALL !


kp

  • Administrator
  • Hero Member
  • *****
    • Posts: 1806
    • View Profile
The ranges are 1 bike in the 8xx range, another in the 6xx and this bike being 778. I've also seen 2 switches sold on eBay over the years. I know this cos I bought one and I think it was Alan Landry who bought the other. I have used the range 650 to 850 as the guide but could just as easily be 500 to 900. I did ask all members to let us know their switch type within range 500 to 1000 but don't recall any response. Nevertheless, I'm chuffed to see the switch on Gutz's 778.
Whatever you do Gutz, keep this bike original. Either restored or lightly rejuvenated, this bike has a ship load of originality and its unique parts inventory, and as others have said,should be retained. Thin lip cover, long choke arm, cast bevel drive instrument drives, small nut tachometer and speedo cables, double wrinkle tank, looks to be original early petcock, 2 hole airbox, early RH switch. Etc etc are just some of the unique parts to this bike.
A photo of the underside of both LH switches would be good, thickness of mirror stems, rear top of brake arm, bottom shot of headstock, under seat, stamped codes on disc, Innside of master cylinder, width of front horn on top triple clamp, is the hole where the 2 instrument rings join together ( where these rings join the front horn of the triple clamp).
Maybe others can add to this list
All very interesting.
KP
Yabba Dabba KP


hondasan

  • Administrator
  • Sr. Member
  • *****
    • Posts: 379
    • View Profile
Great early bike.
Carbs are long choke lever type, but carb vent tubes are 90° angled type rather than straight exit (good picture can be found within Technical/Restoration). Both my long choke lever carb sets have straight exit vent tubes.  Another subtle variant within carb types? What is highest known VIN for long choke lever carb types I wonder?

Chris R.
Chris R.
302/338


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
Great early bike.
Carbs are long choke lever type, but carb vent tubes are 90° angled type rather than straight exit (good picture can be found within Technical/Restoration). Both my long choke lever carb sets have straight exit vent tubes.  Another subtle variant within carb types? What is highest known VIN for long choke lever carb types I wonder?

Chris R.

Great observation on the 90' vents, Chris !  I suspected,  but did not know about 90' vents with long arm.  I do believe you are on to something.


Gutz

  • Newbie
  • *
    • Posts: 9
    • View Profile
778 LIVES!!!!!!

Had a great weekend with more than a few hours to finish the carbs and, yes, she started right up! So oil change, new plugs, new air filter and my first ever carb cleaning and this baby started right up. After a minute of exhaust puke there wasn't even any smoke. Only issue is a very high idle. I tried to adjust down but got to the bottom of the cable adjustment and still didn't work. Ran out of time. I'm just stoked that she runs and that clears the path forward.

On another note, I'm happy this bike can contribute to the collective knowledge on the early CB's. Here are some pics that KP asked for. If there is anything else you guys want to see let me know (in layman's terms) what you want to see and I'll snap a pic.

Here are the clean carbs. I didn't replace anything at this point, just cleaned it up to get running.


Gotta say, these things are pretty.


Post start. Yes haw!


Here are some Pics KP asked for. Let me know if I got what you needed. Not sure about some of them. Couldn't find stamping on the disc, for example.


Don't have the bottom half of the "brown" LH control. Probably why it got replaced.


Brakes are locked up big time. Got the top off.


Is this what you wanted to see? Top of rear brake lever?


If you wanted to know the distance between the instruments, I would say about 3/4".


Need your suggestions on this seat. First off, it only has horizontal seams. I always see horizontal and vertical, it seems. I was referred to a shop that does custom seats and restorations (Danny Gray). I sent these pics and they said $400-$500 to replace vinyl but requested pictures of what it should look like. Not exactly confidence inspiring. Do you guys think this seat is restorable? Do I need new vinyl or just foam and vinyl restoration. Is that a reasonable price?


This is the only tear, but looks totally fixable.



Thanks for all you replies and help!

Gutz


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
the upper triple clamp, you have to measure the distance of the narrowest point of the tongue, the distance is recorded in "distinctions," i can't remember the distance between early narrow and later wide.

looks like the m.cyl reservoir has a leveling ring.... ?

i would suggest buying a red foam and seat cover from Yamiya.  i believe Yamiya sells the stainless trim, belt, screws and clasps.  i think they corrected the clasps and screws, but someone else probably knows better.

Gorgeous carbs !



kp

  • Administrator
  • Hero Member
  • *****
    • Posts: 1806
    • View Profile
There were 2 switches in the earlier photos so a photo of the underside of the very faded switch would be appreciated
The master cylinder isn't an original unit for this bike. Is there another master cylinder
The area of the triple clamp to measure is the front horn where the 2 rings connect Also a photo of the reasons NGOs with screw removed please
The brake pedal is the very early type with the casting flash. Nice.
Don't know about your idle issue Mr Swannie should be able to advise
Yabba Dabba KP


Steve Swan

  • Hero Member
  • *****
    • Posts: 2705
    • View Profile
    • cb750sandcastonly.com
Don't know about your idle issue Mr Swannie should be able to advise

1.  faulty cable action, not smooth slide action or air leaks cause the inability to adjust carburation to idle speeds.

2.  with your cables disconnected from all 4 carbs, do slides all close evenly and completely ?

3.  in closed position, are all 4 slides at the same height ?  (i use a small drill to set all 4 slides in same position.)

4.  with all 4 cables attached and the single cable attached to throttle twist grip, do all 4 slides close quickly and uniformly when hand removed from the twist grip in wide open position?  (use a mirror to visualize the slide positions or use the same drill you set the slide positions with when you assembled carbs.)

5.  air leak at manifold?  when engine running, spray soapy water on rubber manifolds, one manifold at a time.  or use brake cleaner.  if there is an air leak, when using this "spray test," engine rpm will temporarily slow.


Sgt.Pinback

  • Hero Member
  • *****
    • Posts: 695
    • View Profile
5. .......raise.

With brake cleaner.
Cheers, Uli (Leonberg, Germany)