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Discussion Starter #1 (Edited)
2016 RGU wet head bike with stock heads. Adding 11.25 to 1 pistons. Stock C.R. is 10.0-1. Will the C.R. be higher than 11.25-1?
Part number for the pistons is 27000007

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2016 RGU wet head bike with stock heads. Adding 10.5 to 1 pistons. Stock C.R. is 10.0-1. Will the C.R. be higher than 10.5-1 ?


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What pistons? Were they cut specifically for that head, if so, then 10.5:1. or there abouts

If they were cut for a larger chamber head, it will be more. And visa versa.

You can calculate it. You'll need the bore, the stroke, the chamber volume of the head, and the dome volume of the piston as well as the volume of the head gasket.
 

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Discussion Starter #3
They are Screaming Eagle 10.5-1 pistons. The bike has the stock wet heads on it and it’s a 103. I am worried about to much compression and blowing head gaskets. The HD dealer told me it will be ok but not sure I trust that statement.


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How does cam timing effect compression? Not messing with you, I really want to know. Thank's

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Discussion Starter #10
How does cam timing effect compression? Not messing with you, I really want to know. Thank's

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Intake valve close I think is what affect the compression.


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look up the specs for the cam.
lobe separation angle, duration, overlap, intake & exhaust valve lift, etc.
they all work together to achieve different goals.

the only way you'll find the exact compression ratio is to cc the heads.
 

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I called Fuel Moto Yesterday and asked them what there thought were. He said it’s a fine line with that cam and 10.5-1 compression. He said what will dictate how it runs with out pining is the tune. I am just about to call and tell them we are gonna do something else. I don’t want a touring bike that is pinging going down the interstate on a 90 degree day.


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I called Fuel Moto Yesterday and asked them what there thought were. He said it’s a fine line with that cam and 10.5-1 compression. He said what will dictate how it runs with out pining is the tune. I am just about to call and tell them we are gonna do something else. I don’t want a touring bike that is pinging going down the interstate on a 90 degree day.
they will prolly take out some of the ignition advance with a controller.
if you don't trust the people who are going to work on your bike, you won't get anything done.
tuners see all kinds of bikes and riding styles and can tune appropriately.
no matter what you do i would highly recommend a dyno tune.

i've got a stock bike that pings lol
 

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Without knowing exact numbers its a crap shoot as to where you would end with the wide range of tolerances that HD puts out. Just threw average numbers in you may or may not get a pms free motor. If it's truly a touring motor I would want to keep in mind not only the 90 degree days but as well as the fuel that is available. I went through my motor last winter with the knowledge that I was going to get into areas where 89 octane and 90 degrees was going to be what you were riding that day. For a touring motor I would suggest keeping CCP under 200 for no pms. Can 205-210 be tuned? You bet, but throw a tank of 89 off in it and see what you have.

Just throwing numbers in the calculator with 10.5s and the 585 your getting well above 200. To much for me and my riding style. JMO
 

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Discussion Starter #18
The bike is done. 10.5 pistons and se585 cam. The tech said it will be ok. They have done several and had no problems. It is the stage 3 103 kit basically. They have done them on wet heads also. He told me if I have problems to bring it back and they will retune it or fix any problems. We shall see.


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