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Yes, pins line up (thank God), and the crown on these pistons is only about 20 thou taller. I literally would have **** myself had they been a different diameter.
New on left, old S&S Forged Stroker piston right:
Last edited by Mattbastard; Feb 25, 2018 at 12:29 PM.
So with this whole compression release debacle, let me paint a picture.
Originally I wanted the CR's to go right next to the spark plug. I figured I'd push a couple buttons and crank her over just like on my 88" Sporty. Then I discovered these:
which are basically some adapters to turn a 10mmx1.0 hole into a 12mm hole for the ACR's from Harley. The kit in that auction actually even includes the CR's and some wiring.
Again, I was thinking about stuffing them next to spark plug. Yea they'd be sticking out a bit but the tank on these bikes is plenty wide and they still wouldn't be in the way.
Then when I got the stuff back and they didn't have any machining I started sniffing around. Turns out, it looks like there's plenty of meat in the head back on the other side of the dome where the TC103HO has their CR's installed. Not enough for the full length of the CR stem, but enough so I can get my little adapter in there and drill a small 1/8" hole into the dome with the rest of the CR and adapter chilling out in the hole of the rocker box.
Since i'm not gonna deal with explaining all that to a machine shop (and paying one probably a few hundred to have it done) I bought a mini mill and some bits/collets yesterday to do it myself. And I just got back from the Long Beach motorcycle swap meet with a $50 set of Evo heads to practice on so I don't f#$k up my $1100 heads.
Make sure the edge on that piston is perpendicular to the Y-axis:
Then have at it, slowly and surely. Only 15 thou needed to come off each side.
Now on to those practice heads. I did the pilot hole, main hole, and tap all driven from the mill so it's all perfectly straight. I also started the tap with the mill by hand for a few turns, then unchucked the tap and finished by hand so I could feel the feedback better.
Maybe I'll get started on the real heads. I'm worried a bit about the angled squish but there is like 1.5" of aluminum in the head in that spot where I drilled the pilot so it should be good.
Also, you see that black dot with the grey line next to the tapped hole? That's where the casting stops right under the first fin in that area of the head.
Last edited by Mattbastard; Mar 3, 2018 at 08:15 PM.
On the head that had some sensor in it I filled with an aluminum bolt where I used JB Weld as loctite, then milled it down flush. At the time I didn't know if I'd be machining that out at all so that was my fix.
Thanks guys. I know it cost me a bit more than having a machine shop do it but I gained three things out of this:
1. I did it MYSELF! That's very rewarding to me.
2. I now own a tool that will be very useful as long as I own it.
3. I've never seen ACR's in that location on an OEM Evo head, now I know it can be done.
I've been thinking. The actual ACR from Harley requires a 12mm tap. Considering how close that hole is to the combustion chamber on one side and the outside air on the other, I don't think ACR's without that little adapter would be possible on the OEM Evo head. I know the S&S heads can take ACR's but there's a lot more meat on the backside of the head to machine into.
If I ever do another build like this it'll be on a mid 2000's Fat Boy with a balanced TC. Those heads can take the ACR's no prob.
I like the venting through the adaptor better than the oem setup venting to the exhaust port, in case the cr was to develop a leak or stop operating, you would hear it.
Took it easy Sunday, cleaned up the shop a bit but also put some time into the motor.
Installed heads, oil pump, cam shimmed, cover installed, and I vacuumed up that huge mess I made around the mill on Saturday.
I tried installing the stator that came on the bike but the wires were falling apart, and the seal that goes thru the case was being a total bitch so I ordered a new one from Ronnie's.
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