Sprocket Shaft Extension

[SanB2013]

I have a set of S&S Super Stock Generator/Alternator cases that I just had a local shop put the lower end together for me. The flywheels are S&S 80".  When I picked up the completed bottom end the other day there was a sprocket extension shaft stuck on the engine sprocket shaft that I have no idea what it's for.  When discussing the build with the mechanic there was no mention of ordering an extension shaft. It appears to be longer than a stock extension and I'm wondering what I would need a longer/offset sprocket shaft extension for.  At this time I can't ask the mechanic why the extension was there with the motor.  The shop owner is going out of business and this was the last engine build they did before closing the doors.  The owner was not a hands-on guy so I was working directly with the mechanic who at this time is unavailable. 
The extension is 3" long and I don't have a stock one to compare with.

[Ohio HD]

They're used with a wide rear tire kit. Everything is spaced away from the cases to clear a wider tire / swing arm assembly.

[SanB2013]

Here's another picture of the alternator left side and sprocket shaft.

[kd]

The generator shaft is shorter than the alternator engine. So is generator transmission shaft.  It may be to space the drive sprocket out for the longer alternator transmission shaft. (if used) 

[Ohio HD]

I thought about that too, but there's not a lot of difference in the main shafts. I guess I'd put a sprocket on, measure to the case. Put the extension on and sprocket, measure to the case. See what the extension amount is.



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[kd]

The trans main shafts are definitely lots longer for the alternator engine. I don't have the measurements but I have used the short early (up to 64), the intermediate 65 - 69 (intro of the aluminum primary), and longer alternator late models. They were clearly different.  l really don't recollect the difference in the sprocket shafts but one time had someone machine a 56 left case down for an aluminum primary (so I could electric start a high compression stroked pan / shovel) but kept the generator. Quite a bit of material was removed to get the right fit to the "eared" later model case. Maybe the S&S case is similarly shallow for a transmission surface match. 

[Ohio HD]

As above, the shortest chain drive main shaft (11.730") to the longest chain drive main shaft (12.470") is 0.730" difference. That's why I suggest mocking the shaft and sprocket on the motor and measure.

[kd]

I agree. It's strange that the transmission shafts were so widely different in length.  The trans case seemed to me to be very similar except the addition of the ears to support the rear of the aluminum primary. It seemed that the wheel and transmission sprockets would always line up no matter what combination you used.

[david lee]

isnt that why there are different size spacers for the front shaft

[friday]

they be alt cases so 1970 up motor shaft .
the mechanic doesnt know what set up is going to be used . he doesnt know 4 or 5 speed trans , hes built the motor thats it .
you can only search for extension lengths to see what that one is

[SanB2013]

I totally agree. The cases were built based on 1970 up type engine/transmission combinations. After reading previous replies I realized that for different motor/transmission/rear wheel combinations you may need to offset the motor sprocket accordingly.   I think what threw me was that I didn't see the sprocket shaft extension on the parts list or remember talking with the mechanic about it.  Not sure why the part was there but maybe it's the one I will need.

Thanks fir all your input.

they be alt cases so 1970 up motor shaft .
the mechanic doesnt know what set up is going to be used . he doesnt know 4 or 5 speed trans , hes built the motor thats it .
you can only search for extension lengths to see what that one is

[Hillside Motorcycle]

Could it be a form of tool they used to rotate the engine during the assembly process, and simply forgot to remove it?