12.5:1 compression on pump gas?

[gcart2]

can i run pump gas with 12.5:1 compression?

[BadinBlack]

i think you'll be fine as long as you run 91 or 93.

[smithn1683]

12.5 is pushing it. I know you can do 12.25, you will know when you motor starts to detonate. Some factors can play into your favor such as timing. There are some gas addatives that can help out if you dont want to go all out and purchase race gas.

[roundsy]

I'm pretty sure you'll be fine with 93, but I wouldn't run any lower octane

[Benjithx]

I ran 12.5 on 92 octane for a few months with no issues at all.

[gcart2]

well you see, getting race gas wouldnt be a prob, its just its so much ez'r running pump. what about a 1:4 (1 gallon race gas 4 pump) mix. would this be the best way.

[pro-rider46]

um, there is a lot of mixed feelings about mixing fuels, but i think if you run 93 you will be just fine, thats what i will be running here soon. I think if your going to buy race gas, only run race gas, or if you dont like that idea then just run straight pump, you will be fine with 93...

[j_cyrus3]

I have a 12:5.1 and I run 93. No problems here. I have put 89 in it and it ran the same. Only ran 89 when thats all I had though.

[gcart2]

cool i guess i will use pump for practice and 110 for racing. ty. thread closed

[BadinBlack]

Originally posted by gcart2
cool i guess i will use pump for practice and 110 for racing. ty. thread closed
110 won't be good for that compression...

[400exrider707]

The idea is to run the lowest octane possible without detonation or pre-ignition. However some of the more exotic fuels only come in higher octanes and their other benefits may overcome the extra cost. No one can truly tell you if it will be OK or not, a lot of things play a factor. Jetting being one, what else is done to the motor, elevation, and on top of that, every motor is still different. I'd try 93 and see how it is. If you have a bigger overlap cam, that too will help with lower octanes.

Just because it runs on a certain octane doesnt mean its right. I accidenatally ran 87 octane in my 400ex with stock compression there was only a little bit of 93 left in the tank, it ran but very crappy! After seeing that I never even think about trying to put a lower octane than premium in. I know a 450r is different but its how it performs. It runs on 89 sure but it easily outperforms 89 on 93. Look at it that way.

[400exrider707]

Originally posted by FoxHondaRider
Just because it runs on a certain octane doesnt mean its right. I accidenatally ran 87 octane in my 400ex with stock compression there was only a little bit of 93 left in the tank, it ran but very crappy! After seeing that I never even think about trying to put a lower octane than premium in. I know a 450r is different but its how it performs. It runs on 89 sure but it easily outperforms 89 on 93. Look at it that way.

There is no difference in power between 87 and 03, UNLESS, you're not jetted correctly and the 93 octane is "covering up" your problems that occur with 87. This is strictly speaking on octane rating. In fact 93 is harder to burn than 87, it burns at a higher temperature, so more than likely the only thing you're doing besides possibly covering up a problem is making it harder to start. Granted the difference between 87 and 93 is minimal. I always ran 87 in my 400ex, even when I went to an 11:1 piston. If your case is true, then I would check your jetting, if your jetting is fine, then I think your mind may be playing tricks on you. Have a buddy put some gas in your tank either 93 or 87 and run it empty then do the same with the next un-used one and see if you can tell a difference. I bet you cant.:macho

Originally posted by 400exrider707
There is no difference in power between 87 and 03, UNLESS, you're not jetted correctly and the 93 octane is "covering up" your problems that occur with 87. This is strictly speaking on octane rating. In fact 93 is harder to burn than 87, it burns at a higher temperature, so more than likely the only thing you're doing besides possibly covering up a problem is making it harder to start. Granted the difference between 87 and 93 is minimal. I always ran 87 in my 400ex, even when I went to an 11:1 piston. If your case is true, then I would check your jetting, if your jetting is fine, then I think your mind may be playing tricks on you. Have a buddy put some gas in your tank either 93 or 87 and run it empty then do the same with the next un-used one and see if you can tell a difference. I bet you cant.:macho

my jetting is great and I didnt know it was 87 until I was done riding for the day. I filled it up and it ran like crap. I used up all the gas in the tank, I went home and when someone asked "hows it runnin?" I replied with a like crap it bogged down and didnt seem to have the power it did the day before. Come to find out my brother filled up the ATV gas can with 87 and the lawn mower gas can with 93. So I put 87 in it. I put 93 in it and rode the next day, no problems it ran fine. I'm pretty sure I dont have a high compression piston and i'm pretty sure the octane caused it to do that. In the manual it says to run at least 92 octane.

[gcart2]

cool i had a talk with my bro (hes kinda like my manager lol) and we decided 93 all the way.