74 to 80 inch differences
#1
74 to 80 inch differences
Ok.............. tore down my 78 FXS shovel today. It is a 74" that has .70 over pistons installed which would put it a little over 80 inches. I am not liking the shape the cylinders are in. Nothing major but you can barely feel a little scoring on one cylinder. Better to take care of that right now while I am rebuilding the bike. Also the wrist pins feel like they are a little sloppy in the pistons.
What I am looking to do is buy new cylinders and pistons and just make it an 80 inch.
My question is this:
Is the flywheel the same in the 74 and 80 inch motors? From looking at different catalogs I have, it shows the connecting rods and outer cases to be the same. Can I just buy 80 inch cylinders and pistons and be good to go?
Thanks in advance for your answers.
What I am looking to do is buy new cylinders and pistons and just make it an 80 inch.
My question is this:
Is the flywheel the same in the 74 and 80 inch motors? From looking at different catalogs I have, it shows the connecting rods and outer cases to be the same. Can I just buy 80 inch cylinders and pistons and be good to go?
Thanks in advance for your answers.
#2
The 74 has a 4" stroke and the 80 has a 4 1/4 " stroke with .030 more bore than the 74. Your 74 with the .070 overbore is not a 80. To go to 80" you need new wheels, and you will need new cylinders and pistons, since you are past the max the cylinders will go for stock 80 + a .030 overbore. And while you are there, replace the rods, crankpin, and all of the bearings. S$S sells excellent stroker products. There is no "Big Bore" cylinder kit that will make a 74 a 80.
Last edited by AlCherry; 05-28-2010 at 12:00 PM.
#4
The following users liked this post:
rockher_man (02-16-2020)
#5
Thanks for the reply Al.
I definitely am planning on replacing the cylinders and pistons. I was thinking of using stock 80 inch cylinders and pistons if the bottom end was the same on the 74 and 80 inch motors. So you are telling that I have to have new flywheels in order to do this? When I looked up rods in the catalogs, it showed the same rod for both motors.
I definitely am planning on replacing the cylinders and pistons. I was thinking of using stock 80 inch cylinders and pistons if the bottom end was the same on the 74 and 80 inch motors. So you are telling that I have to have new flywheels in order to do this? When I looked up rods in the catalogs, it showed the same rod for both motors.
#6
Thread
Thread Starter
Forum
Replies
Last Post