dieselfitter
Pinnacle OPE Member
I stroked the crankshaft in my 3800 by means of an offset crank pin. I added .094"increasing the stock stoke of 1.319" to 1.413". I posted a thread on this forum("part one").
I thought it would be fun to increase the stroke as much as possible within this saw's crankcase. To do this, I decided to make a 5 piece crankshaft. I split the original crank and cut the counter weights off of the shafts.
I cut two square plates of annealed 4140 and ground them parallel. I tack welded them to prevent any movement while boring the center hole and crank pin hole. I bored the crank pin hole(@ .810" offset(throw) from center.
Here is a pic showing the difference in crank throw.
I cut the corners off the square plates with the bandsaw, pressed in the shafts and ground them round on the surface grinder using a spin fixture. Before I could stuff the crank, I needed to do some work to the case. I trued up the cylinder mounting surface.
I thought it would be fun to increase the stroke as much as possible within this saw's crankcase. To do this, I decided to make a 5 piece crankshaft. I split the original crank and cut the counter weights off of the shafts.
I cut two square plates of annealed 4140 and ground them parallel. I tack welded them to prevent any movement while boring the center hole and crank pin hole. I bored the crank pin hole(@ .810" offset(throw) from center.
Here is a pic showing the difference in crank throw.
I cut the corners off the square plates with the bandsaw, pressed in the shafts and ground them round on the surface grinder using a spin fixture. Before I could stuff the crank, I needed to do some work to the case. I trued up the cylinder mounting surface.