Topic: Rear sprocket cb550 distance between holes not what it should be

[RFogelsong]

So after I got the cover, front sprocket, old chain, and old sprocket completely off and I went to put the new replacement on my 550 I noticed that the distance across the center of the hub from sprocket stud to sprocket stud was smaller on the hub than on the new sprocket.

I am 99.9% sure the hub is the stock one meant for the bike although I know it's been relaced with a 16" wheel.  The parts all match up to the fiche and everything but the studs are roughly 3.5" (~90 mm) apart and the new sprocket holes are 124 mm apart according to spec and physical measurement. 

The question is: what is the correct measurement for a 1975 cb550k1 for the distance from one sprocket stud to its opposite?  Is the sprocket I ordered (from Z1) incorrectly marked as "fits cb550" or is my hub not a 550 hub?

[LesterPiglet]

Did a quick measurement there, not 100% accurate as its on the bike but looks like 120mm.

[Jeff.Saunders]

I believe all the CB500/550 fours used the same sprocket pattern - 4-bolt, 124mm between opposite stud centers and 94mm hole in the middle.

Look at the old sprocket to see if it has any numbers stamped on it.  If it does let me know what they are.  If not, take some measurements.  The center hole, the distance across the bolt centers, the bolt pattern, and the diameter of the stud holes..

[RFogelsong]

The sprocket that was on it comes close to the specs for this sprocket

http://z1enterprises.com/530-JTR476-series-33T-Rear-Sprocket-2100.aspx

except it's a 34 tooth on the bike right now.  It doesn't fit great so I'd bet the distance is like 90 mm stud-stud but the 92 will jam on without too much trouble, it's aluminum.  It is definitely a honda hub and has the 4 bolt pattern but the spacing is just off what it should be. In doing a parts search on Z1 I couldn't find a sprocket that said it was for a Honda that came close to the measurements (the smallest measurement I came up with across the studs with a 4 bolt pattern for a honda was in the 110 mm range and that kawasaki one is like the only one of its kind I found on the site). 

No identifying numbers found, but I counted spokes and came up with 40 which is stock and the brake linkage side is definitely stock after looking through pictures of other stock examples.  The sprocket side hub, however, does look a bit different than what some people are selling on ebay as a "cb550 rear sprocket hub".  Were there other sprocket side hubs that would fit into a stock 550 brake side hub (got it this way from the PO)??

[Jeff.Saunders]

You need to accurately measure the distance across the stud centers, and the center hole.

If the studs are 90mm across and it's a 4-bolt pattern, I cannot find a 530 sprocket that would be a match.

if it's 92mm the stud centers across, there are a number of potential sprockets - but the hole center will determine if it could be one of those.

[RFogelsong]

Not too worried about it as I found a stock cb550 hub that the sprocket will work on.  I'll measure exactly for reference next time it's off (and the axle isn't in the way).