Hi all, reviving an old thread here but figured it best to put it in the main thread about harness restoration.
Im cleaning up some old harnesses and wanted to know what chemical (if any) were used in the ultrasonic cleaner to clean the clear connector covers?  I will likely start with dish soap and have seen mention of bleach being used to remove the yellowing.  But Im reluctant to use bleach as it may help harden the plastic.
Thanks, Steven.

So it would appear it does have the horizontal vent carbs, and the numbers stamped on case halves by sprocket say 975 on both sides, what does that mean?

Hi Chip, sorry for the delayed reply.  Ive been curious about the numbers (sequence numbers) you posted a pic of for a while and thought of them as a better indicator of when the engines were assembled.  For reference, my friends engine #173 has a sequence number in the 8xx range (VIN #540).  Another engine #17x I have pics of has a sequence number in the 2xx range.  So the engines were likely produced, tested and later assigned an engine number.  Eng #173 was likely produced around the same time as your engine, but assigned an earlier engine number, one from an engine which perhaps didnt pass inspection.  VIN 540/173 was built with engine and frame parts in the VIN 5xx range though (no horizontal vent carbs).  Your engine however is a later engine number, but given the horizontal vent carbs were only used on the first few hundred bikes, It may be that the engine originally assigned to your frame at the factory didnt pass inspection and Honda transferred the earlier parts to a later engine and then installed that into your early frame.

It would be interesting to know also if your engine has the early waffle cover too, which might suggest that Honda transferred all the parts from an earlier engine to your cases.

In any case, no reason to doubt the pairing.  There's been quite a few instances of larger VIN/Engine number gaps on early bikes and when you take into consideration the sequence number rather than the actual engine number, it brings a little more clarity.  Thanks for replying.

Hi B6 and welcome!  Would you mind sharing the date stamps (cast numbers, likely to be something like 4.7) on the top and bottom cases please? Also, are there any numbers stamped on the top and bottom halves of the engine cases, near the front drive shaft and sprocket?  These should be matched stamped numbers.  Thanks!  Congrats on the find. 

Hi all, I purchased this a while back as a parts lot and have decided to put the cases up for sale or for swap in the hope it helps someone else complete their project. 

I’m selling a set of Honda replacement sandcast cases, stamped with an early Sandcast CB750 number - EVin 416.

These are in decent used shape. They have not been damaged by a chain break. I have had them professionally repaired in two places - near the points cover, and one of the lower fins. Both pictured.

The engine number is not the tidiest.  I did think of having the number micro-welded up and build the engine up for display but I'm downsizing to the projects I want to work on.  The parts which came with the engine did indicate the re-stamped number is the original engine number.

I can ship this worldwide but it would likely need to go express due to its size.  I do have surface mail option to some countries to keep costs down but it is a non-tracked option.

Good luck with the sale Mark.  I hope it goes to someone here who appreciates the level of work youve put into the bike.
All the best, Steven.

Hi all,
I just went through a comparison exercise with a sandcast owner on this topic.  I know its one which has been touched on in the past but I was just wondering if any conclusion was made about engine sequence numbers (i.e. the two matching numbers stamped at the back of the cases, near the front sprocket)?

It has in the past been suggested/concluded (Im not sure which) that these were stamped when the engine cases had been machined as a pair.   If this is the case, machining the cases would have been one of the first steps in the final production and assembly of an engine, the end product combining the sum of individual parts.  There are many parts in an engine which have been noted to have (likely varying but mostly similar) date codes stamped on them.  But machining the cases could have been the first step for Honda in assembling a group of earlier completed, dated parts into a completed engine.

The casting dates of one pair of cases in my comparison differ, to me indicating that casting dates alone are not an accurate representation of engine production sequence.  As with many parts, they were cast etc then lay in wait until it came time to machine and assemble them.  The stamped sequence numbers would have been applied at a later date to the casting date and these numbers are present, and are matched pairs, on both sets of cases being compared.  This shows that each engine has cases which were machined together as pairs. 

So the information collected was:
Engine 1:
Case Seq Nos: 782
Oil Pump No: 596
Casting date 4.7 Top / 4.11 Bottom

Engine 2:
Case Seq nos: 813
Oil Pump No: 857
Casting date 4.11 top / bottom unknown

So in comparing the sequence numbers (and assuming of course the numbers on the cases were stamped in consecutive order), you could conclude that Engine 1 cases would have been machined earlier than Engine 2, by 31 sets of cases.  The latest casting date present on the halves of the engines is 4.11, similar between both engines.  The sequence numbers suggest a very close machining date for both sets.  However Engine 1 is evin# 4xx,  Engine 2 is evin#1xx.

Further oddities occur.  Its been noted that the first sandcast cases were cast without oil filter locating ribs, and without casting dates.  I have seen this up to circa evin#250.  Steve S noted that his evin#254 has the locating ribs and casting dates.   So this range should be roughly the evin# crossover between the engine castings being revised.  The comparison Engine 2 with evin#1xx has the revised engine casings with a 4.11 casting date and locating ribs.  This supports the argument that the cast date on the cases bears no relevance to the evin# of the engine.

I found this exercise interesting.  Im sure there would have been a core group of engines passing QC without requiring revision, then stamped with evin#'s more closely tied to the production date.   However this particular comparison shows that two engines have been assembled within a short period of each other, but one engine has been assigned an earlier evin# (to perhaps replace the original engine which didn't pass QC).  Again, this is assuming each machined set of cases are stamped with the next consecutive number.

It has in my particular case explained a large frame VIN / engine VIN mismatch in the frame containing Engine 2.  The sequence number of Engine 2 is a more reliable indication of a factory matched frame and engine pair which could be doubted if you only considered the stamped evin# and frame vin#'s alone. 

This is why Im curious if there was a conclusion about the sequence numbers.

Regards, Steven.

Looks like it just sold - the auction just ended.  Anyone here?

Hi all,
I haven't paid much attention to the rods and crankshafts in prior builds so Im hoping someone here might be more attentive!

Im putting together internals for a build.  Ive bought a set of Pre-17000 (c.12000evin) diecast rods which dont have the changes of the later K0 onwards engines.  There seems to be one strengthening rib at the 6 oclock position on these rods, which, compared to these late sandcast, very early diecast rod, does not have this rib.  So I guess Im asking if there are early and later rods between sandcasts and pre-17000 diecasts?  Service bulletin mentions the stronger version of the rods was introduced c. 17000evin.

The second part of my conundrum is the issue of the grub screws present in the crankshafts, near the small end journals.  I can see Mark B's early crank has the grub screws then these went to a flat blade screw head somewhere in the early diecasts.  Then of course these were replaced by peened over balls later in CB750 production.  Has anyone noted these differences?

Thanks!