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Jun 14th, 2026
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Joined: May 2011
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Talk Morgan Enthusiast
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This last week I have had to do the Pinion bolt upgrade, due to the customery extrusion out through the timing cover.
I have a 2012 but the motor was rebuilt in 2014/15 with a new crankshaft due to original compensator issues.
Also had a Centa installed at that time
When removing the timing belt etc to do upgrade, the pinion sprocket literally fell off
It was a very loose fit with almost one tooth of rotation!
I thought this was strange?
The replacement pinion sprocket was a good interferance fit with no slop
Could this be to do with the crank size variation? or was it damage with bolt failure?
When loctite used on the new sprocket it was a good tight fit and as I feel it should be/have been.
Its raining so havent been on a run since upgrade, but the motor seems? to be quieter with regard to tappets etc!
When the pinion bolt loosens the bore of the sprocket is relatively soft and then frets and wears away on the shaft. This is what you have seen and not any difference in shaft diameters.
2021 M3W
2013 M3W - Sold
1971 4/4 2 Seater
1934 Sports
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The shaft diameter difference to which I referred is the output shaft - gearbox side.
2013 M3W 1960 Velocette Venom and the Landrovardo!
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My mechanic just confirmed that my crankshaft and Centa journal go to together with a 'wedding night fit' so that's some good news as my M3W finally starts to go back together.
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My mechanic just confirmed that my crankshaft and Centa journal go to together with a 'wedding night fit' so that's some good news as my M3W finally starts to go back together. Bet it doesn't.
2013 M3W 1960 Velocette Venom and the Landrovardo!
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So he basically told me that these parts almost needed to be pressed together. What do you recommend that I do Phil?
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If they needed to be pressed together they will probably survive. I'll try to post a picture of the problem when I can prise the better computer out of Claire's hands in the morning.
2013 M3W 1960 Velocette Venom and the Landrovardo!
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If they needed to be pressed together they will probably survive. "probably" is better than Morgan engineers' standards so I'll take it. Honestly, after the almost 11 months of debating with Morgan Engineers, with the help and guidance of the Liberty ACE's maker, everything I can imagine has been done for the best results and I'm nearly spent...
Last edited by 3Gs; 11/04/19 11:39 PM.
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  Sorry to put another worry in your saga 3Gs I really think you will be OK if the fit is very tight. Not many failures have been reported. I think my upgrade inserts have found one or two of the weakest examples - including mine. to demonstrate my concerns top picture, above, shows a brand new Centa coupling with a small section of original, unworn, S&S shaft inserted. The picture was taken with back lighting to show the gaps at the bottom of the splines where it does not touch ( minor diameter ) and you can just see a bit of light at the top of the splines (major diameter ) where the fit is better but still not perfect. This design would be OK with a tough alloy steel female spline, similar to the shaft, but the Centa couplings come with a soft steel spline which needs a better fit. The second picture ( also back lit ) shows how it should be.
Last edited by Phil Bleazey; 12/04/19 10:04 AM.
2013 M3W 1960 Velocette Venom and the Landrovardo!
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I've confirmed that there were no gaps upon reassembly but have not asked for it to be taken back apart for photo evidence.
All of this effort is now likely for the next owner as keeping the M3W and ACE#10 is probably not a good marital decision.
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I've confirmed that there were no gaps upon reassembly but have not asked for it to be taken back apart for photo evidence.
All of this effort is now likely for the next owner as keeping the M3W and ACE#10 is probably not a good marital decision.
So, your keeping Ace #10?
2019 M3W Sold and is now in Las Vegas enjoying the showgirls :-)
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