Topic: The strange case of the case protector?

[KingCustomCycles.com]

So why have I NEVER seen or heard of this part before? #2 Case Protector

[Bob Wessner]

No answer for that question.  I'm guessing any of the early 750's had one installed at some point if it saw a dealer service.

[dtmmil]

The early 750s had them, till they went with the 18t sprockets, then there wasn't enough room for them so they discontinued use.

[ekpent]

When the chains were snapping like crazy in the early days that was supposed to stop the dreaded case bashing around the sprocket. Honda probably had to fix a bunch of them.

[dtmmil]

After that is when they went to the larger front sprocket, the problem was the 16t sprocket and weak chains, they went to a larger sprocket for the larger radius for the chain, then didn't have room for the protector anymore.

[Bob Wessner]

I'm not sure how much additional protection it offers, but given the circumstances and limited space for installation, it was about all they could do. I  hope I never get to test its effectiveness. 

[CycleRanger]

So why have I NEVER seen or heard of this part before? #2 Case Protector

You don't spend enough time on the forums!

http://forums.sohc4.net/index.php?topic=60529.0

http://forums.sohc4.net/index.php?topic=55386.5

http://forums.sohc4.net/index.php?topic=91016.0

Etc.

 

[MCRider]

I was in Honda Parts at Burke's Honda in FL when i first saw one. i don't think any CB750 ever came with one from the factory. In my experience we retrofitted them on bikes during the dreaded case breaking epidemic. It was a short lived piece. It along with virtually everything Honda did was a "we gotta do something" exercise. While they figured out why the chains were breaking.

Which I maintain was hydrogen embrittlement from battery acid fumes dripping on the chain when it was on the sidestand. Battery tube was too short and poorly routed.

OCICBW

[VTCBike750]

I got one.

[Swoop]

I got three .....wanna buy one?

[mrbreeze]

I was in Honda Parts at Burke's Honda in FL when i first saw one. i don't think any CB750 ever came with one from the factory. In my experience we retrofitted them on bikes during the dreaded case breaking epidemic. It was a short lived piece. It along with virtually everything Honda did was a "we gotta do something" exercise. While they figured out why the chains were breaking.

Which I maintain was hydrogen embrittlement from battery acid fumes dripping on the chain when it was on the sidestand. Battery tube was too short and poorly routed.

OCICBW

Speaking of Honda saying "WE gotta do something" whats the deal with the locking gas cap? I had a 75-76 style K gas tank with the left side petcock and the regular thumb latch cap. Now I have a 74 tank with right side petcock and the locking cap. Was this something you had to bring back to the dealer for warranty replacement?

[mick7504]

I see that David Silver Spares now has them available again.

http://www.davidsilverspares.co.uk/parts/by-part-number/partnumber_21041/

They seem to be a fairly hot item when they come up on ebay from time to time.

[MCRider]

I was in Honda Parts at Burke's Honda in FL when i first saw one. i don't think any CB750 ever came with one from the factory. In my experience we retrofitted them on bikes during the dreaded case breaking epidemic. It was a short lived piece. It along with virtually everything Honda did was a "we gotta do something" exercise. While they figured out why the chains were breaking.

Which I maintain was hydrogen embrittlement from battery acid fumes dripping on the chain when it was on the sidestand. Battery tube was too short and poorly routed.

OCICBW

Speaking of Honda saying "WE gotta do something" whats the deal with the locking gas cap? I had a 75-76 style K gas tank with the left side petcock and the regular thumb latch cap. Now I have a 74 tank with right side petcock and the locking cap. Was this something you had to bring back to the dealer for warranty replacement?

Yes. It was a factory recall that came out sometime after 1976. I remember the house I lived in when I got the notice, and I moved there sometime after 1976. All known owners of CBs of all sizes, 350, 360, 400, 450, 500/550/ 750 etc, all with the thumblatch,  were notified to bring them in to a dealer for the upgrade to the locking cap.  But by then many of the owners had rotated out, didn't have their bikes anymore and the new owners were not onthe list. I still had my 72 which I bought in 74. I remember getting the notice, which I discarded in favor of keeping my thumblatch.

 It was far later than the oil embargo which occurred in 1974 I think, so it wasn't to prevent fuel theft. Obviously as any key or flat item will open the lock. It may have been after 1978, as I don't recall any CB coming with the locking cap from the factory.  The reason was a safety issue. In a crash the thumblatch could not be counted on to keep the lid closed, spilling gas on the rider and the scene for a potential fire.

As we all know, not all latches were replaced, and the thumblatch is now the preferred item for restorations. It was a pot metal casting, porous and prone to breaking.

[mrbreeze]

Good info Ron.......thanks for that

[754]

 Perhaps if you did a bit more reaearch , you would know of these.
 I believe it is incorrect to say the early ones came with it.. but.. some had them retrofitted.
  They started fairly early, probably 1970, then got discontinued probably around K1 era..
 I think there were alsi aftermarket versions.

[HondaMan]

So why have I NEVER seen or heard of this part before? #2 Case Protector

Long story, but the synopsis:
The original K0 had 16t/45t gearing with 98-link chains that wore QUICK. This caused many abused chains to crash through the engine cases, ruining many engines (that's how we learned what the inside of the 750 looked like early on. ). In early 1970, a "kit" came out to retrofit all 750s with a 17t/48t sprockets and 100-link chain, with the little sheet metal "protector", then called a "guide", that was supposed to keep a broken chain on the front sprocket long enough to eject it out the back of the bike. To some extent, this actually worked.

Starting with the K0 diecast in early 1970, the bikes came with the "kit" installed from the factory. All of the K1 bikes had the same setup, with the guard. Most of the guards got removed when worn chains snagged edges of them and crumpled them up into little balls of steel that made lots of noise and sometimes broke the cases anyway, while the chain was still intact. When the K2 came out, it arrived with 18t front sprocket (still 100 link chain and 48t rear), being overgeared and slow, but it helped reduce the chain wear problem.

[Danno]

the 74 550 had a stiffer version of the chain guide that is cleared for 18 tooth sprockets I believe they fit cb750 if anyone wanted one with an 18 tooth sprocket

[scunny]

both my 79 and 81 650 motors have them ?

[dtmmil]

I was in Honda Parts at Burke's Honda in FL when i first saw one. i don't think any CB750 ever came with one from the factory. In my experience we retrofitted them on bikes during the dreaded case breaking epidemic. It was a short lived piece. It along with virtually everything Honda did was a "we gotta do something" exercise. While they figured out why the chains were breaking.

Which I maintain was hydrogen embrittlement from battery acid fumes dripping on the chain when it was on the sidestand. Battery tube was too short and poorly routed.

OCICBW

Speaking of Honda saying "WE gotta do something" whats the deal with the locking gas cap? I had a 75-76 style K gas tank with the left side petcock and the regular thumb latch cap. Now I have a 74 tank with right side petcock and the locking cap. Was this something you had to bring back to the dealer for warranty replacement?

Yes. It was a factory recall that came out sometime after 1976. I remember the house I lived in when I got the notice, and I moved there sometime after 1976. All known owners of CBs of all sizes, 350, 360, 400, 450, 500/550/ 750 etc, all with the thumblatch,  were notified to bring them in to a dealer for the upgrade to the locking cap.  But by then many of the owners had rotated out, didn't have their bikes anymore and the new owners were not onthe list. I still had my 72 which I bought in 74. I remember getting the notice, which I discarded in favor of keeping my thumblatch.

 It was far later than the oil embargo which occurred in 1974 I think, so it wasn't to prevent fuel theft. Obviously as any key or flat item will open the lock. It may have been after 1978, as I don't recall any CB coming with the locking cap from the factory.  The reason was a safety issue. In a crash the thumblatch could not be counted on to keep the lid closed, spilling gas on the rider and the scene for a potential fire.

As we all know, not all latches were replaced, and the thumblatch is now the preferred item for restorations. It was a pot metal casting, porous and prone to breaking.

so the thumblatch gas cap is the preferred one? I believe I have a tank here from a 76 that has one, but the rubber is bad, is that replaceable?

[KingCustomCycles.com]

Yes, on both accounts.

[xsmooth69x]

do you have the un cropped version of this picture i have no idea what i am looking at...

[bollingball]

King I think there is just to much stuff to keep up with. I have been working on 1949 to 1954 Chevy's since 1964 and still run across something new.

[MCRider]

do you have the un cropped version of this picture i have no idea what i am looking at...

Its a CB750 first off. #1 is the drive sprocket cover. #??   is the transmission/shift linkage cover. On the 500/550, I think these are combined. #2 is the chain guide in question. It fits inside #1, snug up against the crankcases. It covers the front of the sprocket, and the curve of the #1 covers the rear. AS HM says, the guide is not designed to protect the cases, but rather to guide a broken chain out the rear of the cavity. Otherwise, a broken chain would bunch up between the sprocket and the cases and the cases would end up with a big hole in them.