Honda CB750 Sandcast

Short throttle springs

markb · 39 · 11654

kmb69

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Mark, Confirming it is pounds force. 1.2 pounds actual at 58mm. Keith


Erling

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Dare I ask how near original Sand Cast are you gone a do your model?
Now this discussion about short throttle springs. As the original setup could not close properly!
Don't for sure know exactly what change did the difference. Thicker cables or the higher slides some 2/100 mm smaller in diameter
I could use the weak springs for years afterwards without any problems.
Though changed to double cables when that was possible.
Some in this Forum insist on 28 carbtops. Are they modified for 6mm cables?
Do someone still want to use the shorter slides?
Apparently more than me had a problem since Honda gave away new parts which indeed cured the problem.
And I for one never came about to complain.
I shall not tell anyone what to do, but apparently 6mm cables and the 46mm high slides would do, and that still with weak springs!
       Youers Erling.
P.S. Some 10 years ago appeared here in Danmark a Motorcycle History Book (Danish).
In the chapter about our Honda, the author claimed all 4 slides could stick wide open simultaneously!!
I had never a problem with more than one at a time, and do not remember if it was the same every time. It took some time to rectify of cause. But it did not happen that often.
Only the one time outside the camping in Milano (Italy), to start the 1000 mile ride home, all luggage had to come off again, but girlfriend could hold the tank though.
      Erling.


markb

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I am trying to make it as close to original as possble.  I do have shorts slides and new 5mm cables.  Depending on certain factors such as the age of the cables, the routing, etc. there can be problems.  The original parts were used until March 1970 and well into VINs 17000 before Honda changed them.  Obviously they had too because of the potential safety issues.  I will start and ride this bike because I need to know that everthing works.  However, because of the value of the finished product it will be ridden very little.  I have doubts that my odometer will ever see 100 miles (160 km) so I am not going to worry.  Maybe I'll even have a set of later carbs to put on it if I want to ride it more.  If/when I sell it the new owner can change them or not depending on his preference.      
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


markb

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I've been out of town the past few days so I didn't have a chance to get the springs ordered.  I am going to try to do it this week.  I think I have enough information to have them reproduced exactly.  Thanks for everyone's input.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


sancastnorway

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I also need 4 of the short spring if anyone is going to make some or have some for sale. Mail to: jan@tveten.biz.

Jan T.
« Last Edit: May 25, 2014, 10:49:02 am by sancastnorway »


markb

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I ordered them.  I'll put you down for a set and let you know when I get them.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


markb

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I received the springs and they look great.  They have been shipped to everyone who wanted them.  Thanks to all of you who helped nail down the specs and to those of you who helped me order enough to make buying them reasonable.  Just so there's a record, here were the final specs in case anyone else needs to reproduce them in the future:
Material: stainless steel spring wire
Wire diameter, .9mm (.035”)
Free length, 128mm
Outside diameter, 18.5mm
Active coils, 15 ½
Total coils, 13 ½
Closed ends
Load @ 55mm = 1.15 lb.
Mark B
1969 CB750 sandcast #97 restored - Sold Restoration thread link
1969 CB750 sandcaxt #576 - Sold
1969 CB750 sandcast #1553 - Sold
1969 CB750 sandcast #1990 - Sold
1969 CB750 sandcast #5383 restored - Sold Restoration thread link
1970 CB750 K0 restored - Sold
2010 H-D Tri Glide Ultra Classic (Huh?)


DW69K0

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Mark,
Many thanks for making this happen for all of us!
Best,
Duane