View Full Version : Sport Scout bore clearance?

05-11-2007, 01:42 AM
I'm doing a top end on the little tractor and am wondering about bore clearance and your opinion.

I had a little rear barrel scoreing which was cleaned up. Sent out to a proper verticle hone in a heavy duty diesel machine shop. I like these guys and they like my antique american motorcycle projects. Fast and good service, next day turn. 30 degree crosshatch.
They also did an amazing job of closeing up a crack in my barrel - typical intake crack to bore. They hand peened it closed and with the sleeve it's held and looks solid. Old world craftsmanship. Love it! I could explain how to do it if your interested.

So just a ring job for me I figure and have hand lapped in the valves a bit to clean up. Have standard bore pistons. Will hand file end gap on +.010 rings.

Ok- so the mil manu says 0.003
I've been told that 0.005 is fine. Esp if your really dialing the thing up on a regular basis.
Can you run .002?
Nicholson's book says 0.0045

I still have the intake gas wash indent on the cycl. wall.
New pistons next season.

5.5:1 comp - flat head.
So what's your clearance opinion?

Tom Lovejoy
05-12-2007, 12:27 AM
No engine builder, but I have been in a couple of mine and seen others. A big part of it would be what your pistons are I would think. Some expand alot more than others, I have heard 4 or 5 thousands seems to work fine. Seen em set up tighter too, as tight as 2.5 and running good. But also seen em lock up tight quick, several just done machines - locked up tight. I would set it up loose, or if not brake it in real easy!!!
Notes I got from Lee Standley, for a racer SS = ring gap - .018, piston clearance .0075 minimum Heres Lees number - he is the best I have ever known, he loves sport scouts + really fun to talk to, 1 (805)646 - 1618 He has been ridding racing and building SS and others for almost 70 years. If you dont all ready know him, give him a call. You will be really glad you did. He built my bottom end 18 years ago. Hes as good as they get, Tom.

05-12-2007, 01:29 AM
Cool - Thanks Tom.

I just like experimenting and building my own stuff for fun. I don't have a main bearing hone. But I have access to one. Well, the more I tear it down and rebuild it, the more I learn. An Indian is very different in comparision to an HD. Well, the differences are interesting.

Fun - but very time consuming. I love my little tractor, and in turn -it loves me.

Wow! He's right on the outside of clearance spec. Siezing during a race would be very embarrassing. But this shows me that .005 is fine.

I wonder what sort of lightening, flow, breathing mods he has done over the years. Love to talk to him.

I'm trying to figure out the best spot to locate a case breather on a stroke 57. Above or below the main bearing? This is my ponder.