stock 400ex is 9.1:1

 

when I had my 440 kit with the same compression 12/1. I was told I could run pump gas. but was recommended to use 91oct
even with that compression I ran 110 race fuel, it wont hurt it because it burns slower
and give less power, thats why with high compression you need high octane
so to answer your question anything less than 12/1 you can run pump gas
if you run pump gas in a 12/1 or higher compression you get pinging and detonation knock, which can or will break a piston
because the fuel burns faster and generates to much heat and melts or brakes something
I know this because i've seen it happen and Im a mechanic by trade and a 4 stroke motor is the same
in a quad, car, truck, lawn mower. thats why to high of compression and not the right octane can be costly

 

also high comp on a 400ex causes lots of problums. main 3 are blown gaskets/needs rebuild with in a year/ pulls head studs.

my 400ex im not sure what is in side mine but it got rebuilt and i didnt ask if they over bored it or not. but with in 30 hours it blew the gaskets then head studs got pulled and it started burning oil bad and the cam went to **** and clutch basket got eighten up and the cam chain streached and now the motor is nocking and the shift forks are slightly bent.

moding a 400ex is not a safe thing do to air cooling. a stock 400ex runs around 200 degrees. now mod the sucker and your adding a nuther 50-100 degrees easly.

 

440 big pain in th a$$!!!!!

 

Okay, I don't want to start anything here, but if you can't run pump gas in anything 12:1 or higher, then why does the honda manual for the 06 450r's recommend 91 octane or higher? so obviously you can run pump gas. and my guess on why you had to keep rebuilding the motor was becuase you didn't put it together right. i ran my 440 for goin on 3 year and have NOT had any problems.

 

well man a 450r motor is a totaly different motor.

a 400ex is not a good motor to mess with. mine is not stock and after the moding it only took 30 hours for over $800 in parts damage with out labor. now it depends how hard you ride also. i ride as fast as i can go. im always going full throtol so i can get in shape for racing wich im in good body shape n stuff already but...............

if your a slow poke riding and get no parts damage then you sould not have those mods. a 400ex runns hot that is whay other quads come in high compression because they runn cooler.

RUN HIGH COMPRESSION ON 400EX YOU WILL NO MATTER WHAT YOU WILL PULL THE HEAD STUDS!!! REASON YOU PULL EM IS CUZ YOUR MOTOR RUNS TO HOT. HEAT MAKES METAL HOT. THEIR FOR METAL GETS WEAKER AND THE STREACHES AND THAT HOW IT HAPPENS PEOPLE. THAT WHAT UP WIT MU QUAD NOW. HOPE YOU LIKE A BLACK MOTOR, BECAUSE HIGH COMPRESSION = HEET AND STREACHES YOUR STUDDS WHICH = LES PRUSSER ON YOUR GASKETS WHICH MAKES YOUR GASKETS LEAK WHICH= A MOTOR FULL OF OIL. it isnt that bad but i hope you like a ugly motor. go a head do it.

run what ever compression you want. but if you drive fast like you should on high compression you will be sorry if you dont runn race gass to make it runn cooler and a big oil cooler.


du! why do you think quads come high compression now days? cuz they ruinn liquid cooled? du!

 

sorry but i think somebody got touchy there. damn !!! those spelling classes just went right out the window!!!
maybe a diffrent colant like engine ice or evens would have helped you cool it down?? or a bigger rad.???

 

yeah yeah i know what you mean. what your saying is you dont know what your sying. right? 400EX DO NOT RUN A RAD!!!!

 

well man a 450r motor is a totaly different motor.

a 400ex is not a good motor to mess with. mine is not stock and after the moding it only took 30 hours for over $800 in parts damage with out labor. now it depends how hard you ride also. i ride as fast as i can go. im always going full throtol so i can get in shape for racing wich im in good body shape n stuff already but...............

if your a slow poke riding and get no parts damage then you sould not have those mods. a 400ex runns hot that is whay other quads come in high compression because they runn cooler.

RUN HIGH COMPRESSION ON 400EX YOU WILL NO MATTER WHAT YOU WILL PULL THE HEAD STUDS!!! REASON YOU PULL EM IS CUZ YOUR MOTOR RUNS TO HOT. HEAT MAKES METAL HOT. THEIR FOR METAL GETS WEAKER AND THE STREACHES AND THAT HOW IT HAPPENS PEOPLE. THAT WHAT UP WIT MU QUAD NOW. HOPE YOU LIKE A BLACK MOTOR, BECAUSE HIGH COMPRESSION = HEET AND STREACHES YOUR STUDDS WHICH = LES PRUSSER ON YOUR GASKETS WHICH MAKES YOUR GASKETS LEAK WHICH= A MOTOR FULL OF OIL. it isnt that bad but i hope you like a ugly motor. go a head do it.

run what ever compression you want. but if you drive fast like you should on high compression you will be sorry if you dont runn race gass to make it runn cooler and a big oil cooler.


du! why do you think quads come high compression now days? cuz they ruinn liquid cooled? du![/quote]



ok, i just had to take the time out to say. that was the abosolute worst spelling i've ever seen.

 

ok, i just had to take the time out to say. that was the abosolute worst spelling i've ever seen.[/quote]

o arnt you so funny