Originally Posted by Bunny
I was talking to Steve Cooke who is a local Harley expert & restorer - he also owned a M3W for a while. He said:

"The mounting holes at the rear of the motor where the alternator lies are generic across the board. So basically you can put any Harley motor in. They go up to 117". The new M8 motor can go up to 134" with work. It all depends what you want to do. The faster you want to go, the less reliable the motor becomes."

He also recommended the S&S 124" twin cam injection which puts out some serious horsepower although he'd junk the fuel injection and fit a big Mikuni HSR48 carb!
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I guess any of these options would need new engine brackets and probably modified intake & exhaust manifolds. Quite a bit of work.


Andy,

I think he's got his information a bit off, or I do really badly... smile

In '06 Touring Harley motorcycles went to a new primary side bolt pattern, five bolts versus the X-Wedge and all previously made Harley touring motors that are four bolt. The X-Wedge has kept with the "old" style Harley, pre '06 bolt pattern and the left side "primary side" crankshaft setup. In '06 and newer Harleys, they used a full-length splined crankshaft with an internal bolt for the compensator. The post '06 Harley motors and the MORGAN M3W are NOT compatible by just bolting it in place. Forget about the motor mounts as they are entirely different from '98 thru '05. I'm not that familiar with the M8 motors from '16 on, but I believe they may have an even different primary bolt pattern.

IF one were to consider a bolt in, kind of, replacement to utilize the Centa and Centa adapter housing to the Miata trans, you will need to stay with the '98/'05 motors. With that though, you can run the SMOOTH Softail twin cam motors. These are only used in Harley Softail bikes. These have twin counter-balance shafts and are VERY SMOOTH running. Softail and Touring Harleys do not use the same motor mount system. Softails of this era were bolt to the frame directly and the Touring Harleys used rubber mounting to smooth the motors out at idle and on the road. Since the Softail motors are internally balanced, they were still mounted solid to the frame and the actual crankcase was between the two were different for mounting locations.

I believe that Pete Larsen used all Twin Cam Softail motors. ACE# 10 has Harley's 120" double counter-balanced motor and with Pete's proprietary clutch drive setup. If salvaged from a Harley bike stock, these motors came in 88" - 1,442cc, 95" - 1,557cc and 103" - 1,688cc. S&S makes a 124" Hot Setup that will pump them obviously up to 124" and plenty of useful power. These are ALL 45-degree twins, not 56-degrees like the S&S X-Wedge.

There are options for use of these motors with carbs and standalone ignition. ThunderHeart makes a standalone ignition system that uses the crank sensor of the Harley and then you could easily use one of S&S's Super G or Super E carbs. You would need to convert the fuel system to a low-pressure system, 1 to 3 psi on the fuel is all a carb of this nature can handle. Then motor mounts would need to be fabbed up and exhaust would need to be redone probably back to the mufflers. All Harleys were 1.75" tube, not sure on the M3W, but probably 1.75" as well. With the '98 to '05 you can just bolt up the Centa once the rotor is modified for the Centa drive bolt pattern, not too difficult to do.

I hope this helps you all some.

The S&S X-Wedge has been used in many custom bike companies here in the US and along with the Morgan use, there must be 5k plus in use today. This should be ample demand for an upstart company to make replacement parts for the X-Wedge motors.

Good luck with your M3W's and your next motor choice.

Dan

Last edited by Dan_Lockwood; 20/02/23 09:05 PM.
Dan