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- Jan 8, 2016
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Ok Fellas, I've bought several of these 475's here recently after seeing one from out west that a faller/saw builder named Tommy Fales built. I tried to learn as much as possible about that saw and it turns out JJ knew Tommy and shed a little light on that saw. Long story short, Tommy would fall timber with it during the week and race with it on the weekends. My conquest to build a bad ass 475 began there.
Here we go....
Same saw for the most part as a jonsered 2077. 52mm bore. Limited coil.Carb is a wj 28. Dual port w/ windowed piston. Below is a stock jug that a previous owner tried to hack up. But it displays the lowers/uppers well. Notice the lowers opened up to the case.......i understand that a number of jonsered models were like this.
I had three options for a piston with this saw.
The first being obviously a stock piston (left). Stock numbers were 103/124/78. With a base gasket it had .050 squish. Way too much for my liking, but maybe we'll use this piston.
Second, Stihl 064 piston (middle) I've heard these run well but the ring end locations steered me away. The plan here is to add finger ports and I'm not crazy about the idea of flipping the piston around so for this particular build an 064 piston never got much consideration. Not to mention the crown to wrist pin is a tad shorter. JJ mentioned to me that Tommy Fales hot rod 475 used a 272 piston (right). I was skeptical with the prospects of this piston. Due to the shorter skirts and subsequent intake duration and as Randy mentioned the possibility of free porting was very high. Crown to pin was well over 1mm taller so that was encouraging. Let's use the 272 piston, first let's make sure we don't free port.
We're golden!
Had to cut a .025 popup on the 272 piston to set squish at .020 with a gasket. Now on to the degree wheel to find out how much exhaust port and uppers will have to come up. But also to find out just how much intake duration I now have .
Ended up at 106/127/85. Yikes!!!! 85?????? My good friend Joey who is much smarter and knows a whole hell of a lot more than I do about building saws has assured me that I'll be fine at 85. Onward we go.
I plan on putting a 24/28" bar on this saw so I figure 100/120/85 will serve me well. So i set out to grind .060 off the exhaust roof and raise the uppers roughly .060 as well............
Here we go....
Same saw for the most part as a jonsered 2077. 52mm bore. Limited coil.Carb is a wj 28. Dual port w/ windowed piston. Below is a stock jug that a previous owner tried to hack up. But it displays the lowers/uppers well. Notice the lowers opened up to the case.......i understand that a number of jonsered models were like this.
I had three options for a piston with this saw.
The first being obviously a stock piston (left). Stock numbers were 103/124/78. With a base gasket it had .050 squish. Way too much for my liking, but maybe we'll use this piston.
Second, Stihl 064 piston (middle) I've heard these run well but the ring end locations steered me away. The plan here is to add finger ports and I'm not crazy about the idea of flipping the piston around so for this particular build an 064 piston never got much consideration. Not to mention the crown to wrist pin is a tad shorter. JJ mentioned to me that Tommy Fales hot rod 475 used a 272 piston (right). I was skeptical with the prospects of this piston. Due to the shorter skirts and subsequent intake duration and as Randy mentioned the possibility of free porting was very high. Crown to pin was well over 1mm taller so that was encouraging. Let's use the 272 piston, first let's make sure we don't free port.
We're golden!
Had to cut a .025 popup on the 272 piston to set squish at .020 with a gasket. Now on to the degree wheel to find out how much exhaust port and uppers will have to come up. But also to find out just how much intake duration I now have .
Ended up at 106/127/85. Yikes!!!! 85?????? My good friend Joey who is much smarter and knows a whole hell of a lot more than I do about building saws has assured me that I'll be fine at 85. Onward we go.
I plan on putting a 24/28" bar on this saw so I figure 100/120/85 will serve me well. So i set out to grind .060 off the exhaust roof and raise the uppers roughly .060 as well............
