Yep, I see the same thing.

The 603 is a cold beast. If you don't wait at least 15 seconds, it's going to let you know it. Also, it needs the glow when it's warm as well. If you simply crank the key without a glow, it takes a few seconds to start.

The 617 starts and runs almost like a gasser. Just unbelievable with the new valves and new prechambers. No smoke.......no roughness.........just a bit of a low idle.......that's it.

Can't make a guess as to why..........but the two of them are vastly different.