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Thread: 101Crankcase Info ?

  1. #1
    Join Date
    Oct 2015
    Taumarunui New Zealand

    101Crankcase Info ?

    Hi, probably a bit of a newbie question, but there is so much varying information on 1928 37" & 45" bikes and long and short frames etc.
    Apart from the obvious difference in the size of the inlets for the cylinders what variations are there between the 37" & 45" right hand crankcases.
    Cheers Munks

  2. #2

    Re: 101Crankcase Info ?

    The crankcases does differ very little between 37 and 45ci motors. Only the opening for the cylinder has a bit smaller diameter in the 37ci crankcase than in the 45ci version. The cylinder pin bolts has the same distance in between, for both engines.

    The 45 ci version is stamped "P" after the first 2 letters: BG-BGP, CG-CGP, DG-DGP, EG-EGP. BG-BGP is of the pedestal motor mounts version, the rest has through the crankcase bolt. 101 frames had the engines stamped DG-DGP and EG-EGP. There is a minor difference that is fairly easy to alter between the variants, the crankcase ventilation system is different on the BG-BGP engine compared with CG-CGP/DG-DGP and different again on the EG-EGP engines.
    Last edited by Charlie1012000; 05-17-2016 at 10:26 AM.
    Charlie 101

  3. Re: 101Crankcase Info ?

    Also the other noticeable difference is that the 37 motors have a 6 bolt pattern to the top of the heads.

  4. #4
    Join Date
    Oct 2015
    Taumarunui New Zealand

    Re: 101Crankcase Info ?

    Thanks for that. I have a basket case 101 I'm slowly getting together ( 90-95% there now) which is a standard long frame that I purchased with a very early 28 37"motor/trans etc (CG255) which I believe should probably be in a short frame. I have been putting together a later 45" motor and gearbox and have a spare right 37" crankcase which needs work anyway and I was planning to adapt it to take the bigger cylinders but I was wondering about the size of the pinion shafts and bearings etc.

  5. #5

    Re: 101Crankcase Info ?

    Shafts and bearings are the same. The only thing you have to do with the crankcase is enlargening the holes for the cylinders. The diameter on the 45ci crankcase is 77,8mm =3-1/16" at the start and reduces to 74,6mm =2-15/16, about 6,3mm =1/4" down.
    Charlie 101

  6. Re: 101Crankcase Info ?

    Hi Munks where are you based?
    There is a chap in Hobart Tasmania who is making engine casings for the 45 and 37 motors, I went to his factory and they are bloody good.

    This is the owner of the business:

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