when im out on the trail and the engine boggs down a little i hear a raddling noise like something is floating around in there.

 

Could it possibly be pre-ignition pinging. Would sound like marbles rolling around. It that is the case then you need to make your carb richer on the fuel as it is lean. Using the wrong fuel will cause some ping also. If your machine with the compression and timing is set to use regular grade 97 octane then that is what you should use. If you use premium grade you actually are hurting your engine and probably not getting the top performance or miles per gallon.

 

running a higher grade octain than specified by the manufactor will not hurt your motor. almost all atv brands recommend running premium fuel due to higher compression compaired to cars and trucks. the noise could also be misadjusted valves.

 

<div class="FTQUOTE"><begin quote>Originally posted by: muddstudd

running a higher grade octain than specified by the manufactor will not hurt your motor. almost all atv brands recommend running premium fuel due to higher compression compaired to cars and trucks. the noise could also be misadjusted valves.</end quote></div>

Mine says 97 octane, and yes a higher grade will hurt your engine. A high compression for an ATV is around 100psi, (facts are that most Utility ATV's are between 75-90psi) and unless you are up around 200psi it is not advised to run premium.
I mentioned gas because Matt1980 mentioned that it had a bog which would point toward a rich condition, and if it were rich and getting preignition then a ping would result, and preignition could come from a higher octane fuel that would ignite sooner.

 

How can higher octane hurt - well it can cause preignition, burn valves, melt a hole in the piston - just to name a few. These engines run hot to begin with adding more heat certainly is not good.

 

i think that higher the octane like race gas, it burns cooler not hotter. read up on that, i have had all the mechanics that i work with tell me that.

 

what type of atv is it

 

running a premium gas will not hurt youre machine, running regular which is 87 octane will make it ping, not premium.

 

We agree that higher octane gets more power per volume - right? How do you get power - from burning gas. When gas burns it expands the molecules. This generates heat. How do you get more power by decreasing the heat?

Typo error - Yes 87 octane, hit the wrong key for 97 octane.

 

<div class="FTQUOTE"><begin quote>Originally posted by: chenoweth122

running a premium gas will not hurt youre machine, running regular which is 87 octane will make it ping, not premium.</end quote></div>

I stand corrected - you are right. The difference between regular and premium is the the rate at which they burn and the anti-knock properties.
Premium burns slower because of the mixtures that make up gas and reduces pre-ignition which is 'ping'
So maybe the rattle he is having is coming from a too low of an octane gas.
I am almost sure I read someplace that premium burns hotter than regular - maybe because it burns for a longer time (slower). I was always under the impression that it was hotter.

http://www.ftc.gov/bcp/conline/pubs/autos/octane.shtm

http://www.state.mn.us/portal/...=true&agency=Commerce

http://www.oregon.gov/ODA/MSD/.../gas_octane_guide.pdf


Pretty good explanations.