Early 2 Hole Airbox

[kp]

Many may be aware that there are 2 distinct two (2) hole airboxes. The early one has no indents to clear the frame with the 2nd design has somewhat small indents. The 3 hole airbox has a larger indent again. The frame itself was also modified to allow airbox clearance.
My reason for posting is to get feedback on the numbers. I do know that the early 2 hole box was carried through into the 4 digit frame numbers and my belief they were carried through to around the mid teens. This would mean that the second series 2 hole airbox (with indents) is a very rare item to find
Anyone have thoughts on my comments

[Steve Swan]

i'm confused.  i always the the 2nd type airbox upper case was the more common type, the relief in the upper case being given so so the factory would not have to beat nearly half flat the frame tubes to clear the 1st type upper case which had no relief.

this is what i have in "Distinctions," it's about as clear as mud........

33. no relief on upper air box cover, We have no information that "no relief" features on upper covers between VINs 674 to 1553

[kp]

Indeed Mr Swan, confusion is the key word. I have a no indent that came off a mid 8xx frame and a 2 indent box that came with bike 1683. I'm assuming that the airbox I purchased of the 8xx framed bike was original and am fairly certain that the box fitted to 1683 was original to the bike. Other than that My memory is a no indent box was fitted to 4 digit frames but this is but a memory/thought/recollection, certainty nothing concrete hence we need to get some feedback. Maybe some wood will contribute to this dilemma.

[Sam]

For what its worth, #410 has the original frame and airbox. Indented frame and no indents on the 2 hole airbox.

[Steve Swan]

ok.  now i'm 4/10th less confused.  the frame was flattened for no relief on airbox.

later frames less flattened, more airbox relief.

forgot those aspects.

so are we suggesting the frames were flattened longer than the airboxes were relieved ?  or no relief airboxes were used for a longer period in the production run than relief airboxes ?  and frames were flattened longer in the production run......?

sheesh.

[Wayne]

You guys make it hard to keep up .... but I'm trying This is what I have so far on the air box situation. I'll make any changes as needed if I can follow the bouncing ball!

http://cb750sandcastonly.com/new/tech/frame_group_11.html   

[corsa65]

Just to add to the confusion.. Frame 1630 has a 3 hole air box and the frame has reliefs. But I think mine is an anomaly.

Lester

[Sgt.Pinback]

Just to add to the confusion.. Frame 1630 has a 3 hole air box and the frame has reliefs. But I think mine is an anomaly.

Lester

Now I am cufused.

According to disriction list and parts list the airbox stay changed with # 4007 from 2 to 3 holes.

[Steve Swan]

You guys make it hard to keep up .... but I'm trying This is what I have so far on the air box situation. I'll make any changes as needed if I can follow the bouncing ball!

http://cb750sandcastonly.com/new/tech/frame_group_11.html   

Wayne, we're bored and it's the middle of winter......

[hondasan]

#302 came with original 2 hole no relief airbox. The frame is machine indented (ie not beaten in by hand). The indents are pretty well forward facing(maybe 10° round from straight ahead), ie not matching up to the shape of the airbox at all well. In fact, I recall there were rub marks where the airbox upper was against the frame in spite of the frame indents.

#1120 has frame indents which are identical (shape, size, and orientation) to those on #5298. The indents in both of these frames are facing approx. 45° round from straight ahead - hope that makes sense. Neither of these came with original airbox. #1120 would of been a 2-hole, but with or without relief? #5298 would of course of been 3-hole.

If anyone has a VIN near to 1120 with original airbox, is it relieved or not?

Chris R.

[kp]

You guys make it hard to keep up .... but I'm trying This is what I have so far on the air box situation. I'll make any changes as needed if I can follow the bouncing ball!

http://cb750sandcastonly.com/new/tech/frame_group_11.html   

OK that's very enlightening for me as I've not owned a Sandcast over 2000 that had anythying like original airbox. This clearly indicates the 2 hole is more prevalent than I certainly realised. I wonder why they are not more freely available even in cracked condition. It is not as if they are difficult to repair 🤔

[vnz00]

VIN 1853 has the indented 2 hole airbox.
Regards, Steven.

[kp]

VIN 1853 has the indented 2 hole airbox.
Regards, Steven.

Hi Steve, Your bike is as good a yardstick as any bike in that range one will ever see. It was the most unmolested bike I've ever seen.

[bojje]

Hi!
None of my earliest (#24/43 and #180/302) sandcast has matching aircases but #388/407 has. Unfortunately the aircase is at my painter to be plasticwelded and painted. I'll visit him soon with more parts to paint and I'll make a check. About frames, #24 has no dents at all, #180 has handhammered dents and finally #388 has toolpressed dents.
Best regards, Bo

[Steve Swan]

Thanks Bo, for that great information.  The relief on  232's frame tubes also appear to be hammered, definitely not clean press marks.