In the rush to publish most moto-journalists repeated what Harley Davidson Factory Reps fed them about the new 8 valve engine. Fortunately the Ray’s Motorcycle Diary staff has no deadlines or need to be the first to get to print. RMD is never invited to the roll out of any new factory models. Shame that, but it does allow me to think about what I am being told.
I do think the new Harley Davidson 8 valve engine is a big step forward, giving riders what they have been asking for, a cooler running engine and more horsepower. Harley showed that with good engineering an air cooled engine can make decent power and meet emission requirements.
It seems that everything that was changed on the engine, was a change for the good and in some areas appear to be brilliant engineering. So would I say that the 8 valve appears to be the best engine the Harley Davidson has made? I think the answer lies in what was not changed.
Probably the most problematic area of the Twin Cam engine was the chain driven cams. In 2002 Harley Davidson dropped the double tapered-roller crank bearings in favor of the less expensive plain-roller crank bearings. The plain-roller bearings allow excessive crank end play. If there is excessive end play gear drive cams cannot be used. Gear driven cams make for much more precise valve timing and the chain driven cams and tensioners on the Twin Cams motors caused problems throughout the Twin Cams life span.
When asked why Harley Davidson did not use the more expensive but superior double tapered-roller bearings on the new Milwaukee 8, Harley’s Chief Engineer of New Products simply said, “We didn’t see a need to use double tapered-roller bearings.” Further Harley claims they kept the chain driven cams to lower engine noise, which allowed them to have louder pipes, now it's not a flaw it's a feature.
So is the new 8 valve the best engine Harley has ever made? I don't think so because Harley Davidson didn't build the best engine they could using the best available technology, and worse, they know they didn't. This engine is, well, just good enough.