[flatbutt]

Originally Posted by Jeff Higgins

The 103 would be a Twin Cam, and by most accounts the best of that breed. The 107 would be the Milwaukee 8, an entirely different engine that replaced the Twin Cam.

The Twin Cam is, to me, an inherently better design. It fixes the problem with horribly splayed pushrods shared by all single camshaft Harleys up through the Evo and inexplicably reintroduced on the Milwaukee 8. The Milwaukee 8 also introduces four valve heads, a needless and silly complication on a motor that will never see even 5,000 rpm. Another needless complication is the water cooled heads introduced on later TC Electraglides (but not on other TC models) and carried through to (I believe) all M8 models.

The difference in idle you feel is because HD made a conscious choice to lower the idle speed on the M8. It idles several hundred RPM lower than the TC, which many complained "didn't idle like a Harley". I'm sorry, but all I can hear at that super low idle is the sound of rod bearings and wrist pins self-destructing.

Anyway, real world experience with my TC 103 Road King since I bought it in 2013 tells me it is a fantastic motorcycle. A worthwhile upgrade over the TC88 it replaced. Not just a bigger motor, but one with all of the early bugs worked out. Plus the new frame, and a six speed transmission. And Brembo brakes. Would an M8 be a big enough upgrade to entice me? I've test ridden several. Still have the TC.

My 114 really has what I feel is a very rough idle. Other than that I haven't any sump issue or performance complaints. Then again I only have 8000 miles on it.

Yet when I was considering the purchase most MOCO riders told me that the M8 was a good motor.