compression
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Joined: Jun 2010
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From: Door County, WI
compression
So over winter I'm looking to reseal my motor and get my heads redone due to mileage. While apart I wanted to up my compression. I already have an EV27 cam, open air filter and short shots. I'm wondering what kind of piston to use to get a 9.5:1 ratio. Andrews cams said anything over that would make for hard starts and higher octane fuels. The budget doesn't allow a big bore kit so pistons are to me the best choice here. Any input would be appreciated.
Dirt don't hurt
Joined: Jan 2011
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From: Haslet Texas
Are you able to run on pump gas?
Elite HDF Member
Joined: Sep 2007
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From: Bluffton, South Carolina
There are many manufacturers that make pistons, and even more that sell "rebranded" pistons. We think Mahle makes a quality piston that has enough "bells and whistles" without making it too sophisticated. Add to that the fact that we've had zero problems with them. Hope this helps.
John
John
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Joined: Jun 2010
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From: Door County, WI
And that's a good question too. Can you run pump gas? I ride this bike a lot now and don't wanna compromise to much if any driveability.
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Joined: Sep 2012
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From: almost there
Yes I use regular high test pump gas and rode all summer in the GA heat, no ping. The heads are ported polished with larger valves and springs and the heads are considerably shaved down. I put a Yost power tube in the S&S E carb to get my 50 MPH.
MY build is: Ev27,lifters, adj pushrods, roller rockers, Head work,Weisco 10.1 pistons bored 30 over, Dyna ignition, S&S E. Cometic gaskets, S&S cylinder studs and S&S head bolts.
Im getting 205 lb compression on a cold cylinder. Engine starts so easy you just bump the start button. Runs great and dependable. I highly suggest with this build the Cometic gaskets and S&S cylinder studs & S&S head bolts.
MY build is: Ev27,lifters, adj pushrods, roller rockers, Head work,Weisco 10.1 pistons bored 30 over, Dyna ignition, S&S E. Cometic gaskets, S&S cylinder studs and S&S head bolts.
Im getting 205 lb compression on a cold cylinder. Engine starts so easy you just bump the start button. Runs great and dependable. I highly suggest with this build the Cometic gaskets and S&S cylinder studs & S&S head bolts.
Last edited by aces&8s; Oct 14, 2013 at 08:12 AM.
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Road Warrior
Joined: Jul 2013
Posts: 1,476
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From: Florida
The big boyz calculator puts cold cranking compression @ 186.8 with an EV27, stock cc heads, and a .040 cometic hg. You would be perfectly fine on pump gas, I would not shave heads much, if at all, just to be completely safe. I'm just quoting hypothesis, obviously it works for aces.
Seasoned HDF Member
Joined: Sep 2012
Posts: 6,570
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From: almost there
YEP, but the "Head work" is where it's at. If ya dont have a good head job, dont go there. You need a complete package to make the air flow properly [Head job]. Sorry but this does sound sexual and the power is orgasamic...Just came back from a nite ride and dammit man.....AAhhhhh.. Anyone got a smoke........
Last edited by aces&8s; Oct 14, 2013 at 07:11 PM.