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I need some dimensions from a 28t cam gear. I have two fully assembled singles and can't measure the back of either of the cam gears without pulling the head and removing the gear.

If you have a gear out I would like to know the total thickness on the hub, front to back. Also the distance that the hub protrudes past the back of the gear disk. What model did the cam gear come from?

I am specifically interested in w/c, don't know if n/c is different.

thanks,
Jack

12.75mm front to back. 4.1mm from the back face of the gear. These are from narrowcase 250’s.

Matt

12.8mm front to back. 4.15mm from the back face of the gear. Seem to be identical. These are from a widecase 350.

cheers Hans

Jack,
I can offer some info-
The attached photo shows, left to right, a round case 750 twin gear, an unknown gear, and a narrowcase single gear. The middle gear was on a narrowcase tower shaft, with the snap ring- the way I and others usually save these gears to keep gears with matching grinding marks together, but I don't remember taking a widecase engine apart, so I probably got it with one of my basket cases- can't be certain.
The left(twin) gear is 16.5mm thick with a 5.75mm shoulder, the middle gear is 17mm thick with a 5.75mm shoulder, and the right(narrowcase) gear is 12.5mm thick with a 3.75mm shoulder.
The twin gear pair is part number: 0755.29.60
There a 3 different part numbers for the wide case single gear pairs:
0606.29.600 for a 250
0608.29.600 for a 350
0615.29.600 for a 450
I don't have any clue how to tell the 3 wide case gears apart, but with different numbers there's a good chance they're not the same.
The 750 twin tower shaft/camshaft gear pair are 21x28.
The widecase single gear pair is 20x28, so I doubt if the twin gear would mesh with a single tower shaft- must be some crazy gear module since gears with
the same number of teeth and pitch diameter should be the same module and the gears look to have the same pitch diameter.
It won't be hard to tell if the gear is several millimeters too long or short, but the how to tell the difference between the 250/350/450 gears will take some research.
Rick

After thinking about these gears a little more, the factory only offered them as a pair, so the different part numbers were probably the different lengths of the tower shaft, and the 28t camshaft gear is probably the same in the 250/350/450 gear sets.
Rick

Thanks for the info, it fills many of the blank spots I had. Yes the part numbers are for pairs, and the length of the tower shaft is one of the differences between sets. I don’t have a n/c parts catalog for the numbers. The following summarizes what we know from measurements:

??? n/c; 12.5 mm
250 n/c; 12.75 mm
0606.29.600 250 w/c single 20T/28T set; 182?/?? mm
0608.29.600 350 w/c single 20T/28T set; 202/12.8 mm
0615.29.600 450 w/c single 20T/28T set; 202/(14.5..14.75 calculated) mm
0755.29.600 750 twin 21T/28T set; ???/16.5 mm
0759.29.600 860, 900 twin 21T/28T set; ???/16.75 mm

Comments:
* Singles have 20T on tower and 21T on the crankshaft, it is reversed on twins
* Differences of 0.25mm are probably not significant, definitely not from the unfinished back of the gear
* The 202 dimension is the total standing height of the tower gear I have from a 450, 182 is stated by an eBay seller
* I calculate the 450 value based on measurements of my 450 head and the 860 gear.

My conclusion is that the 28T cam bevel gear is the same for all singles, n/c and w/c, and twins except for the thickness with that difference in the length of the rear hub. Since I need a gear for my 450 and I have one from an 860 I’m planning to take 2.2 mm off the back of it with a surface grinder.

Jack