416 on pump gas???

[frenimy]

Most people say that an 11:1 piston is good for pump gas which I have seen many people say is 93 octane. I have only been able to find 91 octane at the gas stations. is this sufficient or is it nessesary to use 93 octane fuel with this setup.

[slow96hater]

it probally would be fine. 93 is the gas i use, but im from michigan. depending where your at in the world, premium octane levels are anywhere from 91-93. try it, listen for spark knock, and make sure your motor dont get hotter then it should while its running. 91 should be fine.
if your real worried about it, buy the 91, and buy some octane booster form some auto parts place.

[zrpilot]

It depends on many things. Here are some of the variables:
Actual static compression
Cam specs (dynamic compression)
To some extent the exhaust system
Temp
Elevation
Riding conditions (Duning, for example)
Quality of available gas

I have an 11:1 416EX that would rattle on everything BUT 110 octane race gas.

I'd say that if your going to build 11:1, make sure you know your gas options... because, like me, you may be forced to run race gas.

[Ruby Soho]

i have an 11:1 440 that i run on pump gas and its fine:confused:

[400ex28]

I run 93 in mine but i also get some pinging sometimes.. 11:1

[zrpilot]

The last two posts is exactly my point. One 400EX may run fine on premium pump gas, while another will deto on premium.

[400ex28]

I just run 101 in mine, they have it on a pump here.

Stock 400ex you are required to run a minimum of 92 octane. My quad ran like crap when I accidentally ran a lower octane, it would bog and stuff. Highest compression I will go with is 10:1. I dont like 11:1 because your on the edge and theres always a chance of needing a higher octane.

[Brauap]

Is it safe to run 91 w/ 10:1?

[Wheelie]

Every quad is different. ZR hit the nail on the head.

My quad runs fine on pump gas with about 11.5:1 compression. However, at the dunes I run 50/50 due to the extra load/heat and low elevation. I only run pump gas in the woods at 1800+ft elevation.

I believe pump gas works well in my case is the combination of aggressive cam and stock CDI (conservative timing).

[400exrider_88]

i heard with a high compression piston, having a aftermarket cam will make it lose compression. such as a stage 2

[Wheelie]

Originally posted by 400exrider_88
i heard with a high compression piston, having a aftermarket cam will make it lose compression. such as a stage 2

This is partially true. The quad may lose a bit of dynamic compression due to the increase in cam duration and changes in lobe seperation. The effect will be less pronounced as rpms increase.

[400exrider_88]

if i have a stage 2 should i still run high octane fuel or not?

[Brauap]

you can if you want...

[big_ed2008]

I thought i might point out that my owners manual calls for 92 octane on a stock '99 400ex. Not sure if its the same for all years, but i found this interesting.

[Brauap]

I know, I saw that too ... (03) But I always run 82.. thats 10 less.. but it use to run fine.. hhmm..