I am sure its plenty fast but is it what I need? The local track is a pretty large 1/10th scale dirt track. Actually most of the racers (90%)race 1/8 scale, small 8th scale track. Its a indoor track. I received a 17.5 motor with the purchase of my b5m lite. I dont have any want to drive in stock class, will never do it. Do you guys think I will be happy putting the 17.5 motor in or just jump to a 8.5-10.5 turn motor? I think I would like the 17.5 to get used to the buggy , but also think I am going to get bored with the lack of speed real quick. I also run a 8.5t 2wd short course truck .

If geared correctly 17.5 motors are pretty fast, that said if it's primarily an 8th scale track you may just be better off motoring up to make some of the larger jump sections.

Put it in first and run it against other 17.5t buggies....

No.

Make the jump Luke! You will be much happier with an 8.5, and a 10.5 will blow the doors off your 17.5

I would go to a 7.5t for 2WD buggy.