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13th Grave
03-22-2007, 11:59 AM
I got a 416ex and it has the 11:1 high compression piston in it, it came like this when I traded I want a 10:1 so I can run pump gas but I'm having trouble finding one, If anybody knows where to get one please help me out, also looking for a repair manual.
JOEX
03-22-2007, 09:27 PM
Originally posted by 13th Grave
I got a 416ex and it has the 11:1 high compression piston in it, it came like this when I traded I want a 10:1 so I can run pump gas but I'm having trouble finding one, If anybody knows where to get one please help me out, also looking for a repair manual.
I think you should be able to run 92-93 octane with that compression...
underpowered
03-22-2007, 09:58 PM
pump gas is fine on 11:1. i run 93 in my 11:1 426 when race fuel is not available with no problems
Got Boost
03-22-2007, 10:13 PM
you can run pump gas 91 + till 11.5:1 so you should be fine.
13th Grave
03-23-2007, 12:25 AM
The person I got it from told me not to it might be 11.5:1 I'll check and get back with ya.
GPracer2500
03-23-2007, 02:43 AM
Seems like most people report being ok with 11:1 pistons on 91+. It wasn't in my build. If I ran staight 91 pump it would deto. I was pumping ~180psi cold at 1300ft.
400exrider707
03-23-2007, 07:07 AM
I ran 87 a few times on my stock bore 11:1 wiseco, with a thin cometic head gasket. With the thin gasket I think it put it close to an actual 10:1. Remember the 400ex advertised compression ratios are not correct!!! The pistons are designed for the xr400 motor!
EXriderO2
03-23-2007, 08:16 AM
i live right around upstate new york and i have a 11.1 piston in my 400ex with sparks timeing key and hot cams and just the typical intake and exhaust mods and i run 93 pump gas and mix the proper ammount of octane booster in my tank.
ilpadrino113
03-23-2007, 10:03 AM
I ran 87 a few times on my stock bore 11:1 wiseco, with a thin cometic head gasket. With the thin gasket I think it put it close to an actual 10:1.


wouldn't the thin gasket raise the compression??
400exrider707
03-23-2007, 10:14 AM
Originally posted by ilpadrino113
wouldn't the thin gasket raise the compression??

yep... it still ran fine the very few times I did run 87.


exriderO2, the sparks timing key also makes it run hotter due to the advanced ignition as well.