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General Category => General Discussion => Topic started by: rjamesohio on December 18, 2019, 09:53:36 AM

Title: Crank Differences, early to later big twins
Post by: rjamesohio on December 18, 2019, 09:53:36 AM

I've started laying out the parts to my G5, and since I have two roundhead motors I have been laying out the parts to compare.

As I was looking at the two cranks, I noted there is a vast difference in the crank nose on what I think is a later crank (pictured). The other one has a tapered nose that I believe was probably to accommodate the early alternators.

Therefore - to run the earlier alternator setup I'd probably have to use the other crank, not this one. But I'm guessing that this crank could be used with the later and more effective alternators.

Can anyone confirm or provide more details?


(https://i.ibb.co/BqVDJ4L/Crank-Nose.jpg) (https://ibb.co/BqVDJ4L)

Title: Re: Crank Differences, early to later big twins
Post by: Antietam Classic Cycle on December 18, 2019, 11:17:59 AM

Quote from: rjamesohio on December 18, 2019, 09:53:36 AM

I've started laying out the parts to my G5, and since I have two roundhead motors I have been laying out the parts to compare.

As I was looking at the two cranks, I noted there is a vast difference in the crank nose on what I think is a later crank (pictured). The other one has a tapered nose that I believe was probably to accommodate the early alternators.

Therefore - to run the earlier alternator setup I'd probably have to use the other crank, not this one. But I'm guessing that this crank could be used with the later and more effective alternators.

Can anyone confirm or provide more details?


(https://i.ibb.co/BqVDJ4L/Crank-Nose.jpg) (https://ibb.co/BqVDJ4L)

Yes, Bosch (and Saprisa) alternator crank nose is short and tapered, Ducati crank nose is long and straight.

Title: Re: Crank Differences, early to later big twins
Post by: rjamesohio on December 18, 2019, 04:38:13 PM

Quote from: Antietam Classic Cycle on December 18, 2019, 11:17:59 AM

Yes, Bosch (and Saprisa) alternator crank nose is short and tapered, Ducati crank nose is long and straight.

Thanks Charlie, I suspected that in general. Do you know if the later crank will work with an early timing chest cover? For example - with this engine I had planned to use an analog tach so I need the mechanical tach drive front cover but have not fitted everything up yet as the cam is a bit tight in the front bearing and I need to check that.

Thanks my friend - there's seldom a road in Guzzidom where someone else has not been down before you ;)

Ron

Title: Re: Crank Differences, early to later big twins
Post by: Antietam Classic Cycle on December 18, 2019, 08:17:16 PM

Quote from: rjamesohio on December 18, 2019, 04:38:13 PM

Thanks Charlie, I suspected that in general. Do you know if the later crank will work with an early timing chest cover? For example - with this engine I had planned to use an analog tach so I need the mechanical tach drive front cover but have not fitted everything up yet as the cam is a bit tight in the front bearing and I need to check that.

Thanks my friend - there's seldom a road in Guzzidom where someone else has not been down before you ;)

Ron

The timing cover wasn't changed as far as I know, so it should be a direct swap.

Title: Re: Crank Differences, early to later big twins
Post by: dblue on December 20, 2019, 11:13:33 AM

The throw can be different on the late crank, 78mm or 82mm depending whether it is a 950 or 1064cc,