Topic: Should my front sprocket have a "fixing plate"?

[DHuffman]

Hey guys, Ive noticed the bolt holding the front sprocket to the output shaft on my '77 CB750F has a tendency to back off. I haven't been riding it yet, but I need to address it before I do. I am using a 3/8" offset spricket from Cognito Moto, which has 2 holes to accomodate the "fixing plate". However, the sprocket that was on the bike when I got it did not have this, just a washer and a bolt that threaded into the shaft ( I dont remember if it had the two bolt holes for the plate). When I look at the parts list for a F1, I see the fixing plate. Did the F2 not have them? Did it have any fail safe to keep the bolt from backing out or should I just loctite it?

Thanks!

[Jerry Rxman Griffin aka MuthaF'er]

The 77/78 F and K used the large washer and bolt not the plate like the earlier models.

[seanbarney41]

I was surprised and slightly wary of how the front sprocket on my f3 mounts as well...i just blue loctited it and all was good.

[DHuffman]

Okay - loctite it is. I realized  I was looking at a schematic for a 76 (F1), which was causing my confusion.

Thanks!

[754]

 I had one come out on the road, started wearing on chain guard but sprocket stayed on.
 I have a 78 motor in a Mr and the 78 sprocket cover did not easily go in so I used the early one.
 Unknown to me and I only found out last year, the 77 and 78 sprocket cover have a boss cast in to prevent the bolt coming out.
So use loctite and if you must, trim a late cover to make it go in easier, or figure out the wiggle in right trick..

[madmtnmotors]

Why are you using an offset sprocket on a later model (77/78) 750?

[seanbarney41]

Also, the 77/78 sprocket should only have a shoulder on 1 side, so it is overall, thinner.  That way the bolt and washer tightens down onto the end of the shaft and the sprocket is left with very slight wobble and play.

[PeWe]

Loctite is good on the early models M6 sprocket bolts too. I had one lost and no 2 close to escape a few years ago.

After this thread locker Loctite 222 which is a weak model but perfect for vibration protection. The threads get a plastic like goo that affect the entire removal of bolt. I use it on many bolts.

I do not recall what I used back in the 80's.
Same type of Allen head M6 bolts with washers. Maybe "locking" washers.

[DHuffman]

Also, the 77/78 sprocket should only have a shoulder on 1 side, so it is overall, thinner.  That way the bolt and washer tightens down onto the end of the shaft and the sprocket is left with very slight wobble and play.

How crucial is the wobble? The shaft does not protrude past the face of the sprocket on mine oh, so the bolt and washer will tighten against the face of the sprocket. If I can find some small washers that would fit inside the splines on the sprocket then I could maybe put them in there and get it to tighten only on the shaft.

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[DHuffman]

Why are you using an offset sprocket on a later model (77/78) 750?

I have a 160mm tire so I needed to bring the sprocket over to clear it. See my build thread in the project shop forum

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[seanbarney41]

Washers or spacer is probably ok, just be sure to use high quality hardware.  I dont know how important the play is, only that honda engineers meant it to be there.  Are you a better engineer than those employed by Honda in 1977?  The sprocket you bought is probably designed for a 71-76.  This is usually the problem with poorly designed 530 chain conversion kits.  I think folks have just went with bolting the too thick sprockets on tight in the past, but no idea if it worked, or for how many miles.  Whatever you do, check up on it often, a failure here has the potential for disastrous results.

[DHuffman]

Washers or spacer is probably ok, just be sure to use high quality hardware.  I dont know how important the play is, only that honda engineers meant it to be there.  Are you a better engineer than those employed by Honda in 1977?  The sprocket you bought is probably designed for a 71-76.  This is usually the problem with poorly designed 530 chain conversion kits.  I think folks have just went with bolting the too thick sprockets on tight in the past, but no idea if it worked, or for how many miles.  Whatever you do, check up on it often, a failure here has the potential for disastrous results.

Absoultely. By my measurements, the distance from the face pf the sprocket to the face of the shaft is ~3.25 mm. I found a couple washers that when stacked make about 3.45mm. I put them on the bolt and tightened it up. The it some play on the sprocket now - but no idea how it compares to what a stock one had.

[madmtnmotors]

Your chain will likely hit the outer upper rear of the front sprocket cover. Check it closely after assembly.

[DHuffman]

Your chain will likely hit the outer upper rear of the front sprocket cover. Check it closely after assembly.

It does. I was planning on grinding it away like my friend Excellrec did:

[madmtnmotors]

Your chain will likely hit the outer upper rear of the front sprocket cover. Check it closely after assembly.

It does. I was planning on grinding it away like my friend Excellrec did:

That should fix it!

[seanbarney41]

Yeah, I would probably be happy with those washers.  No idea exactly how much slop is built into the stock set up and it would be very inconvenient to get my f3 out and measure.

[754]

 The pic in post 13 us earlier sprocket cover , it can rub on master clip  even more if sprocket has a bit of wiggle.
 I just finally put my 78 F cover on my 78F motor, it had early cover and was rubbing.
 I filed a very small amount off in 3 places and it now goes in easy.. it's a 74 frame.. that may change things.
 I am looking for that thread with video to add info.. if I don't find it I can add it herel.