Topic: How do you ID the later style clutch cover in a CB750?

[Jerry Rxman Griffin aka MuthaF'er]

OK, moving right along with my little project. I'm upgrading my clutch pack to the later style to help prevent the annoying Honda clutch rattle of the earlier 750's. I'm going by info put out by Honda as I'll post below. As you'll see there is an upgrade aka Field Fix for the older 750's that doesn't require tear down of the engine. It involves removing the outer friction disc and replacing it with a thinner metal disc to make room for a GL1000 Clutch Plate B. That is the top portion. Below that is the updated engine mod with the serial numbers when it started. This used a wider clutch basket, etc.

So, from studying the info, my question is:

How do you visually identify items #4 and #5, ie the clutch cover and the clutch lifter piece that was installed on the later engines vs the earlier engines? I have 3 covers (one of which was from my earlier engine) and they all look identical. Widths look identical. The 3 lifter pieces all look the same length but the diameters are 7mm and 8mm and appear to be the same lengths.

[scottly]

Here are a couple of pics from a K7, 27046xx. I recall reading somewhere that a late clutch cover hits the clutch basket when installed on an early motor? The webs stick out further or something.
On part #4: that is the part pressed into the bearing. If you are referring to the pin that goes inside it, the pin measures 7.8mm.

[madmtnmotors]

Here are a couple of pics from a K7, 27046xx. I recall reading somewhere that a late clutch cover hits the clutch basket when installed on an early motor? The webs stick out further or something.
On part #4: that is the part pressed into the bearing. If you are referring to the pin that goes inside it, the pin measures 7.8mm.

Scottly,
     You're close... but you're off 180 degrees. The early model clutch cover will interfere with the taller clutch pack stack of the later models. The offending portion of the early clutch cover (can't cite the model years) is one of the three screw bosses for the outer tin cover screws. Specifically, the screw boss closest to the kicker shaft protrudes an extra 1/4" further than the other two. This is enough to interfere with the clutch hub (it was enough to pin mine in place) but the extra material (about a 1/4") can be ground away without exposing the thread pocket for the tin cover screw. I had replaced the friction disks on my 750 K8 and had a chromed clutch cover for an earlier model laying around and opted for the bling. Bolted it together and the clutch would not budge. Careful inspecting revealed the gouges on the clutch hub and corresponding marks on the protruding screw boss.

    Soooo.... check for uniform height of the three screw bosses where the outer tin cover bolts on. The one near the kicker shaft will protrude an extra 1/4" into the space required for the clutch hub on some early model clutch covers. Again, this material can be ground away with no ill effects, just don't grind too much!

    One other caveat, there are EARLY, EARLY, EARLY clutch covers that actually had a different bolt pattern (one extra or one less than later models, I can't remember which) but I don't think the bolt pattern will even bolt up, so any issue with these would be fairly obvious.

[HondaMan]

    One other caveat, there are EARLY, EARLY, EARLY clutch covers that actually had a different bolt pattern (one extra or one less than later models, I can't remember which) but I don't think the bolt pattern will even bolt up, so any issue with these would be fairly obvious.

The sandcast covers had one less screw in the cover and cases.

[scottly]

    Soooo.... check for uniform height of the three screw bosses where the outer tin cover bolts on. The one near the kicker shaft will protrude an extra 1/4" into the space required for the clutch hub on some early model clutch covers. Again, this material can be ground away with no ill effects, just don't grind too much!
   

Ahh, this may be the key. In my pics, that boss is slightly lower than the web.
Other than that issue, any clutch cover should work on any year, aside from the very early ones?

[Jerry Rxman Griffin aka MuthaF'er]

OK, findings:

My known 75 750F cover that is/was painted black like the engine - that one screw boss is rounded and protrudes above the web by 2.2mm and the rod/pin is 7.83mm in diameter.

The one that I had powder coated to match my engine is identical to this one     Not good but could be worse.

My other spare that is not painted and has that boss flattened out (like Scottly's), does not protrude above that web but the rod/pin is 7.05mm

Other observations: The thicknesses of the covers appear to be the same so that's a non-issue. That was what I kinda expected to see. Part #4 (thanks Scottly) is just an updated bushing (?) that has a different diameter hole to match the different diameter pin(?). By golly, I see what appears to be a man-made dimple on the clutch center hub that Wilbur alluded to created by the longer round headed boss that I must have caused.     

Considering we have 2 different diameter pins, do we have the same length pins? You guys have any insight on that?

Up next, remove the lifter/pins and measure lengths and make my observations of the #4 piece/bushing/whatever and report back. Can't see that the differing pin diameter affects actual operation of the clutch. And also grind that boss flat so I can use my nice powder coated cover  I just so happen to have a spare 75 750F engine laying here that I can/will use as a model too.

Thanks guys.

[scottly]

Part #4 dimensions:
hole ID = .433"
hole depth = .260"
flange thickness = .079"
flange OD = .858"
body OD = .668"
overall length = .419"