HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
BigMike

Race gas, Pump gas,

21 posts in this topic

Manual says to use 95 octane . Well around here 92 is the norm. So anyone using race gas or are we all just plugging away with pump gas?

Share this post


Link to post
Share on other sites

I'm very new to these thumpers, but it's my understanding that race fuel is unnecessary. 93 octane is OK.

Share this post


Link to post
Share on other sites

You have to be aware about what is going on with octane rating. Octane is C8H18, a specific hydrocarbon, that is used as the standard for the rating the fuels resistance to detonation. Any fuel you test that detonates like pure octane will have an octane number of 100. There may not even be any actual octane in it. Octane numbers lower than 100 have less resistance to detonation, over 100 have more.

There is RON, the research octane number, which is derived by analytical chemistry. Then there is MON, Motor octane number, derived from actual testing on a specific motor (apparently you can buy these standard test motors if you want). One gives a higher rating than the other (I can't remember which is which). Then there is (R+M)/2, the average of the two, which is what you see on the pump.

According to the guy I work for, this (R+M)/2 is the result of the congress at the time. He was involved in a group of energy consultants that was given the task of deciding which method should be used to rate octane at the pump. His group came back with a recommendation to use one or the other, but whatever you do DONT AVERAGE THEM! Which is of course what was done. If you have MON, you can calculate RON, and vice versa. Apparently when you average them, you lose info and can't accurately get RON or MON back. As I am writing this, I don't quite get this but I know this is what the guy told me. If anyone is really curious I will get clarification from him.

I think Yamaha publishes thier bikes requiring RON or MON (someone look in the manual please). I don't recall it being (R+M)/2, which is the rating you see at the pump in the US. They are different, and yes it seems like it was done just to confuse us.

Share this post


Link to post
Share on other sites

I have a 2000 426, and I run 76 brand 110 octane mixed with 92 octane. I have tried using strait 110, and strait 92, but the mixture of the two works best for me. I live 500 feet above sea level, and my fuel screw is 2 turns out.

P.S. Does anybody know of good aftermarket brake pads to get these 2000's slowed down better?

Share this post


Link to post
Share on other sites
Originally posted by BigMike:

Manual says to use 95 octane.

The octane rating at the pump and the rating called for in the manual are not the same. 92 pump gas is fine, heck I run 91 and I have higher compression (13.5:1, but I’m at 4,000+ ft.).

I’m sure race gas would work better but you would probably have to rejet.

Share this post


Link to post
Share on other sites

Around here the highest was have at the pump is 92 (r+m/2). The only other option is strait race fuel from the local (30+ min trip) race track or to buy some of that make your own race gas mix. Has anyone run the stait 92 in your bike and if so did it seem to run OK?

Share this post


Link to post
Share on other sites

I've owned my 99yz400 since Oct. so I haven't really had a chance to ride it in the heat. I live in San Diego and ride the tracks as well as the local desert all of which are low elevation and I have only run 92 octane. I haven't ran race gas so I can't really compare it but I have not noticed any problems what so ever with the 92.

Khris

------------------

When in doubt, GAS IT!

Share this post


Link to post
Share on other sites

Do Not Run Race Gas in your 426. Even most of the pros just use pump gas. Just make sure the gas is clean going in. All the mags I have read sugjusts just pump gas. Race gas can cause damage to your bike. 92 octane has served me well for over a year. Follow your manual.

Share this post


Link to post
Share on other sites
Originally posted by brooks:

Do Not Run Race Gas in your 426. Even most of the pros just use pump gas. Just make sure the gas is clean going in. All the mags I have read sugjusts just pump gas. Race gas can cause damage to your bike. 92 octane has served me well for over a year. Follow your manual.

I don't understand how race gas could damage your bike. If you have too much octane it will not hurt anything it just wouldn't add any hourse power.

In fact octane does not add horse power it just prevents HP loss. On a hot day I will run unleaded race gas or my home brew in my 2000 LS1 Camaro. I do this to prevent knock.

The Camaro has over 10K miles on it and a dozen passes at the track (12.50).

My guess is since our bikes do not have knock sensors you could tear one up quick if it started knocking.

If you could point to the info on why race gas is bad I would apprecaite it.

Thanks,

------------------

Rick

01 YZ426F #85 Vet C

Share this post


Link to post
Share on other sites

I believe that you only NEED to use race gas if you've had your engine modified and its necessary to run race fuel because of the mods.

------------------

Livin the life in Port Huron, MI. I'm 15 with a 426!

YZ 426's suck!(all the air they can get)

THROTTLE JOCKEY. .....because all golf courses should be motocross tracks!

[This message has been edited by teamtoxic (edited 02-16-2001).]

Share this post


Link to post
Share on other sites

Just out of curousity I tried a mix of 1 gall of VP 110 octane and 2 gall of 92 octane pump. I realize you would probably have to re-jet, but with my standard jetting (168 main, next leaner needle, 2 1/4 turns out on fuel screw) in my 01 426 it basically lost all the mid-range pull I had picked up by going to the leaner needle. Its back to 92 octane for me!

Share this post


Link to post
Share on other sites

I think the common sense factor goes into play here. Just like in a hi-po car engine with higher compression, there sometimes is a need to run a higher octane gas to prevent pinging. This also allows you to run a quicker advance in your ignition. Upper cylinder temps are cooler too I think. THE COMMON SENSE FACTOR IS THAT YOU ONLY NEED THE HIGHEST OCTANE FUEL TO THE POINT THAT YOUR ENGINE ISN'T PINGING (pre-ignition)IN IT'S CURRENT CONFIGURATION/STATE OF TUNE! If you're not experiencing this in your 426, then common sense dictates that you don't need higher octane fuel than what you're running. Your just wasting your money. If it currently runs fine on premium unleaded, stay with it.

Share this post


Link to post
Share on other sites

It seems like this subject has been discussed a few times in the past, and as I recall the consensus was that race fuel will damage the seals in the carburetor. I run 91 octane fuel(the highest pump octane in my area) and have not had any problem.

Share this post


Link to post
Share on other sites

It seems like this subject has been discussed a few times in the past, and as I recall the consensus was that race fuel will damage the seals in the carburetor. I run 91 octane fuel(the highest pump octane in my area) and have not had any problem.

Share this post


Link to post
Share on other sites

It seems like this subject has been discussed a few times in the past, and as I recall the consensus was that race fuel will damage the seals in the carburetor. I run 91 octane fuel(the highest pump octane in my area) and have not had any problem.

Share this post


Link to post
Share on other sites

I tried a couple of combos of race/92mix

and this is what i found with my 99

I tried 50/50 vp110/pump92 and i got horrible milage. but seemed to rn cooler.

I tried 25/75 seemed a little beter but bad milage and still ran cooler.

Then tried 20/80 and still no diff in milage but seemed to have more pwr than straight 92pump.

so racing in hare scrambles i need the milage worse than the horse pwr.

After all it is a 400f how much more hp is needed.......I know I know.....there is never enuf HP but sometimes you just have to weigh things out!

And it does run just fine on 92

I may try to go to a 10/90 mix just for the temp factor in the summer though.

$.02

G4

------------------

ride BLUE

Share this post


Link to post
Share on other sites

Too high of an octane rating will burn valves. Low octane fuel burns quicker (more likely to ping) High octane fuel burns slower. If you use fuel with a higher octane rating than is needed, then fuel will still be burning as it passses the ex. valve. Thus, burning it. Eventually you'll start to lose compression and need to have your valves ground. Running a tank or two of race fuel won't do much damage. Always running it will cause problems.

Higher octane won't get you more power, it'll just resist pinging more. Run the 92 octane fuel. If your bike has a problem with detonation, then try some higher octane fuel.

Paul

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0