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Author Topic: 80" EVO EV-27 and 9.5:1 Pistons  (Read 1654 times)

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ltank

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    • CVO1: 2000 FXR4 S&S V111, CustomS.S. 2-1 exhaust, Primo-Rivera OD 6 speed, 49mm Custom Front End Ohlins 30mm Fork cartridges , Hyperpro Shocks, Barnett Scorpian Clutch
    • CVO2: 1983 88" Shovelhead Won the World of Wheels 1985 Sept 85 Issue of Hot Bike Mag
    • CVO3: 1989 FXRS, 1990 Custom 100" Shovelhead/ EVO
80" EVO EV-27 and 9.5:1 Pistons
« on: March 04, 2022, 02:46:00 AM »

I have a 1998 80" EVO. Road King. I was gonna hop it up a bit. I found out it already had some work done.
EV-27 cam, the 138 bearing, adjustable pushrods,
S.E. high flow carb baking plate with air filter, the 40mm CV carb has the jetting done and other things.
And a S.E. ignition module.
    The pistons are stock flat tops and in perfect health. Is it worthwhile to get KB920C 4032 Forged
9.5:1 pistons? They have a slight dome but say that compression is 9.5:1 with 80cc head volume. If the heads have to come off why not just shave the heads
More and keep the stock pistons?  If I shave the heads to 80cc how much needs to be removed?  Then use Cometic. 030" head gaskets to get 9.75:1 corrected compression.  Will the EV27 be OK with that. The motor has 37k miles. Should I replace the lifters too?  Any thoughts or input is appreciated. Thanks
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HOGMIKE

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Re: 80" EVO EV-27 and 9.5:1 Pistons
« Reply #1 on: March 04, 2022, 09:12:09 AM »

I went down that road years ago, slowly increasing HP and TQ over the years,
Starting with the EV27 cam.

Ask yourself what are you going to use the bike for as you go through the process.

My bike ended up with a S&S crate motor when I finished and way fun to ride, but I spent time and money until I was satisfied. My goal may be different than yours but it was still a fun journey along the way!

That evo motor is still a 95” sidewinder with Andrews 72 and headwork and runs great, but not as fun as the crate motor. It’s now in storage waiting for a basket case bike to bolt in to.

It was a fun project.
JMHO
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HOGMIKE

johnsachs

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Re: 80" EVO EV-27 and 9.5:1 Pistons
« Reply #2 on: March 04, 2022, 04:41:01 PM »

I have a 1998 80" EVO. Road King. I was gonna hop it up a bit. I found out it already had some work done.
EV-27 cam, the 138 bearing, adjustable pushrods,
S.E. high flow carb baking plate with air filter, the 40mm CV carb has the jetting done and other things.
And a S.E. ignition module.
    The pistons are stock flat tops and in perfect health. Is it worthwhile to get KB920C 4032 Forged
9.5:1 pistons? They have a slight dome but say that compression is 9.5:1 with 80cc head volume. If the heads have to come off why not just shave the heads
More and keep the stock pistons?  If I shave the heads to 80cc how much needs to be removed?  Then use Cometic. 030" head gaskets to get 9.75:1 corrected compression.  Will the EV27 be OK with that. The motor has 37k miles. Should I replace the lifters too?  Any thoughts or input is appreciated. Thanks
I still do a fair number of 80" Evo's with stock pistons, and EV27 cams. Mill the heads to 78 cc., use a .030" head gasket, install Pig Tails in the drain back area of the cylinders, good base gaskets, and a legit 42 MM. Mikuni, for the icing on the cake, and I'll bet you'll be an extremely happy person. Probably be in the area of 80 h.p.  ;)
John
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ltank

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    • CVO1: 2000 FXR4 S&S V111, CustomS.S. 2-1 exhaust, Primo-Rivera OD 6 speed, 49mm Custom Front End Ohlins 30mm Fork cartridges , Hyperpro Shocks, Barnett Scorpian Clutch
    • CVO2: 1983 88" Shovelhead Won the World of Wheels 1985 Sept 85 Issue of Hot Bike Mag
    • CVO3: 1989 FXRS, 1990 Custom 100" Shovelhead/ EVO
Re: 80" EVO EV-27 and 9.5:1 Pistons
« Reply #3 on: March 05, 2022, 05:12:56 AM »

This will be spare motor to run while any of our bikes are getting  repaired. My 98 RK has a S&S V124 with 55k miles, FXR4 S&S V111 has 65k miles
Big brother 94 Ultra Classic Electraglide has 68k miles, son's 94 FXSTC mileage unknown.
« Last Edit: March 05, 2022, 05:18:13 AM by ltank »
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