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bottlefed1
03-01-2011, 01:41 PM
Im getting my 400 fixed and the guys I took it to said that it needed a new piston and he is replacing it with a weisco 12:5.1 piston I also had him order a stage 2 cam,and i will be getting a slip-on. Would i be able to get away with using 91 octane?
honda400ex2003
03-01-2011, 01:46 PM
nope... why would you let him put a 12.5:1 in there? 11:1 is highest you will be going on 91 and the added work involved with a 12.5:1 is quite extensive in the way of other mods besides what your mechanic is most likely going to do. i.e. hd head studs


just my .02 though,
steve
bottlefed1
03-01-2011, 02:01 PM
its been broke for almost 2 years. I just lost interest in it but i decided to get it fixed so I took it to a local guy he took it apart said that it needed a new piston i told him ok and figured since it was apart i would put a cam in it. I told him i wanted a cam and he said stage 2 hot cam i said ok. and left it at that and figured he knew what he was doing.
bottlefed1
03-01-2011, 02:23 PM
its been broke for almost 2 years. I just lost interest in it but i decided to get it fixed so I took it to a local guy he took it apart said that it needed a new piston i told him ok and figured since it was apart i would put a cam in it. I told him i wanted a cam and he said stage 2 hot cam i said ok. and left it at that and figured he knew what he was doing.
bkelley
03-01-2011, 02:52 PM
Still, 12.5:1 is pretty extreme for normal riding. I'm with Steve, drop an 11:1 in with a stage 2 cam and stay pump premium safe.
honda400ex2003
03-01-2011, 03:05 PM
if it was my machine, i would be on the phone telling him to put an 11:1 in there before it is too late...


steve
VTredneckgames
03-02-2011, 06:37 AM
I agree. Unless you like running atleast 100 octane at $9 a gallon.
CJM
03-02-2011, 06:47 AM
Yep, you need at least 100+ octane if you put a 12:1 in b/c of the heat it generates cause the EX is air cooled.

11:1 is the highest I would go.
bkelley
03-02-2011, 11:57 PM
It's not the heat, it's the detonation.
slightlybent47
03-03-2011, 02:10 AM
It really depends on what type of riding you do and if you want to run race fuel or not.
I’ve run MX on a 416 with a 12.5 to1 for years and with stock head studs with zero issues.

Race fuel is a cleaner burning fuel. I get much less carbon build up.
82toyota
03-03-2011, 03:40 AM
Originally posted by bottlefed1
its been broke for almost 2 years. I just lost interest in it but i decided to get it fixed so I took it to a local guy he took it apart said that it needed a new piston i told him ok and figured since it was apart i would put a cam in it. I told him i wanted a cam and he said stage 2 hot cam i said ok. and left it at that and figured he knew what he was doing.



so u live in Tulsa, Ok...... who is the local guy....jnh racing......
if so that guy is no good just saying......or is it sandtrax...
crownandmonster
03-03-2011, 06:55 AM
Originally posted by VTredneckgames
I agree. Unless you like running atleast 100 octane at $9 a gallon.


$9 for 100 octane?! I don't like paying the $6.75 for 112 sunoco, 9 bucks for a gallon of 100 and I'd really be crapin my pants.
honda400ex2003
03-03-2011, 07:08 AM
then you better call the shop and get the 12.5:1 out of there if you dont like 6.75 a gallon. not only will you be paying more, youll be burning more when you have to tune it with a bigger main jet.


steve
sneaky11
03-03-2011, 07:18 AM
Hey guys... I pay 5,50$ the gallon for 94 octane here in Quebec... So if I can put 112 for 6,75$ in my 12.5:1... be sure I wont cry on this!

If you want to build less compression,. just use the OEM 400ex head gasket. I donno where exactly you gonna be, but surely under 12:1