M8 Crank. What can be done to it?

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Feb 17, 2020 | 07:06 AM

AbitNutz

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Joined: Mar 2018

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From: SW Ohio

M8 Crank. What can be done to it?

Can you do the Timken bearing modification to an M8 crank and still keep the balance shaft? Or am I talking nonsense? It could go either way.

Feb 17, 2020 | 07:41 AM

dawg

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From: Vermont

Dragos offers a different crank for the M8 with a dual Timken setup. That said, I don’t think you can do the Timken conversion on the OE crank but I’m not entirely sure.

Feb 17, 2020 | 08:20 PM

NorthWestern

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From: Inland NW

Is there an issue, or weak link? I knew about the TC crank mod, but I was not aware of anything going on with the M8. Big power build?

Feb 17, 2020 | 08:46 PM

Mattbastard

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Joined: Nov 2009

Posts: 4,315

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From: Tampa

Quote:

Originally Posted by dawg

Dragos offers a different crank for the M8 with a dual Timken setup. That said, I don’t think you can do the Timken conversion on the OE crank but I’m not entirely sure.

Dual Timken? You mean one on each side of the crankshaft?

Feb 18, 2020 | 07:13 AM

martin10

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Joined: Jul 2014

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From: VA

Quote:

Originally Posted by AbitNutz

Can you do the Timken bearing modification to an M8 crank and still keep the balance shaft? Or am I talking nonsense? It could go either way.

The M8 bottom end is very strong. And I haven't heard of any issues with it. Unlike with the Twin Cams.

May 30, 2021 | 06:42 AM

Spivitz

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Joined: Sep 2019

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From: Jonesborough Tennessee

Quote:

Originally Posted by martin10

The M8 bottom end is very strong. And I haven't heard of any issues with it. Unlike with the Twin Cams.

So you see no issue increasing 114 M8 displacement to 128 on a stock bottom end?

I was told it would be playing Russian roulette with my 2005 if I bumped displacement on the stock 88cubes without addressing the bottom end.

I understand my 2021 & 2005 motors are "a bit" different 🙂

May 30, 2021 | 06:57 AM

Mchad

Club Member

Joined: Dec 2014

Posts: 10,734

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From: SWFL

Call Darkhorse and talk to them. They know all things about Harley bottom ends. Plenty here have put 128’s on stock cranks/bearings though (me included). Unless you beat the living hell out of your motors you’re likely fine staying stock. However, I expect nothing beats the smoothness and piece of mind blueprinted crank. Last I saw it’s about $1800 for a soup to nuts rebuild including a timkim from Darkhorse.

I’ve got .005 runout (edit: on the pinion shaft) on my Dyna which while well within spec, isn’t fantastic so I’ve been thinking about it.

Only problem is it’s about a 5 week turnaround, which is tough to swallow.

Last edited by Mchad; May 30, 2021 at 08:41 AM.

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May 31, 2021 | 09:40 PM

Max Headflow

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Joined: Dec 2005

Posts: 19,863

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From: poway

The M8n has a 1.75 inch crank pin where the TCs only had a 1.671. The M8s seem to be a bit stronger. I guess you could steel plug the ends if you needed a little bit more.. (DH trick)