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#596884 - 09/20/19 07:45 AM RACE GAS vs. PUMP GAS
rockin_s Offline
TON Member

Registered: 04/22/15
Posts: 77
So I thought I would seek the "expert" advise from the racing community that has experience, not just knowing what they read about this topic. I have always ran Premium pump gas in my 2016 2 stroke. Sometimes ethanol free, sometimes not. But I only buy what I need for the ride so that it doesn't site for months at a time. At approx. 45hrs I am seeing signs of detonation in the head. I am wanting to switch to VP gas. Mainly for the consistency of the fuel which would be better for the engine. Looking for thoughts about what fuel others are using in 2 strokes. This is a race bike but running stock engine.


#596887 - 09/23/19 12:55 PM Re: RACE GAS vs. PUMP GAS [Re: rockin_s]
Xray Wombat Offline
New Member

Registered: 12/15/18
Posts: 2
Loc: Dallas, Texas
Octane should be the main difference. A 2-stroke complicates matters because a small amount of oil is being burned. Oil reduces octane. Aside from that, the temperature of the engine, the head, plug tip, etc has an effect and certanly will change as you run. By 45 hrs you mean the fuel is 45 hours old? Ethanol in fuel increases anti-knock but also steals power since it converts to less when burned. It might be possible for some ethanol to evaporate in the heat, but how much, and is it a factor?

Maybe you are very close to the type of detonation that's bad enough to hear and some small factor is pushing it over the line.

I don't have much modern 2-stroke experience but do have old-style non-computerized hot rod car experience and there were times when the so called premium fuel detonated. The fuel formula changes from summer to winter, who knows what they do to it. In the summer, it was best to buy VP or other consistent fuel a couple octane points higher than needed to put an end to detonation.

One thing that comes to mind if your bike has a seperate reservoir for the 2 stroke oil is whether the delivery is constant. How many hours of riding does the reservoir hold? Does it deliver consistently until it's empty?

I can only suggest the best fuel & a little more octane if you are racing and aso a cooler plug, but not sure how that would affect fouling in a 2 stroke. Hopefully someone will comment on this but there isn't much to go on.

Edited by Xray Wombat (09/23/19 12:59 PM)
[] '95 XR600R []'94 XR350R [] '96 Wolverine 350 4x4 [] '71 M35A2 [] '72 M818 customized->'M8109' []


#596892 - 09/24/19 08:46 AM Re: RACE GAS vs. PUMP GAS [Re: Xray Wombat]
DonS Offline
Gang Member

Registered: 06/19/13
Posts: 213
Loc: Texas
If the pump gas octane exceeds what your manual calls for, might be some other factor.

I won't put ethanol in my bike. Have made it 6+ years without having to do so.

I used C12 (mixed with K2 at 32:1) for 2 years in a 13 YZ250 and had absolutely no problems.

VPR has gotten stupid expensive.

FWIW I'm on a 4st now, using QT non-ethanol mixed with T4 at 3:1.

You can search for non-ethanol gas near you here: https://www.pure-gas.org/

I use this for calculating octane amounts: http://www.bazellracefuels.com/Calcs/OC1.htm


#596896 - 09/26/19 03:45 PM Re: RACE GAS vs. PUMP GAS [Re: DonS]
rockin_s Offline
TON Member

Registered: 04/22/15
Posts: 77
Thanks for the feedback


#596902 - 09/30/19 07:55 PM Re: RACE GAS vs. PUMP GAS [Re: rockin_s]
Irishcoffee Offline
Veteran Lunatic

Registered: 08/17/02
Posts: 2925
The big Buckees have high quality non-eth at reasonable prices.


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