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natebal

alternate fuels?

5 posts in this topic

Have heard some scuttlebut regarding fuel and octane ratings. Read a few responses to one post where a guy blew up his xr650, showed pix of the toast motor, and it was suggested that it must have been caused by running as little as one tank of 87 octane "pump gas" though it and pushing the bike hard. I've heard these bikes are bulletproof. How can a tank of leaner gas fry it? There was mention of deto failure as the ancilary culprit? Furthermore there was discussion of running 94 octane as the fuel of choice for the xr650L.

In san diego where I live the premium "pump gas" is 91 octane. With a stock lean bike and this fuel am I running this bike too hot, with potential motor worries?. Where do you get the 94 gas is it aviation fuel? does it really matter. Any help appreciated, Nate

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That bike had a high compression piston in it. That made it much much more sensitive to low octane than a stock bike. That bike had a 10.25 to 1 piston. If I remember correctly a XR650L is more like 8.5 to one. I believe Honda says regular is OK for a XR650L. I have the owners manual for my XR600 and it says use a research octane of 91. That corresponds to a pump octane of 86 to 87, or regular. The XR600 has a compression ratio a little higher than the 650L at 9 to 1. While I normally run premium, I have run regular when I had no choice and I had no problems. The reason that I use premium, is that the bike will ping under hot high load situations.

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Somewhere online I read that air cooled bikes should use premium (93). I dont know the reasoning for that because of the low compression, you would think 87 would be fine.

Does anyone have a knowledgable answer to that?

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My L used to ping on regular (that's all I could get at times in some nowhere land gas stations) on hot days under load, I run a little on the lean side since everywhere I ride is up in altitude from the Valley, I run Shell V Power in my bikes now not so much for the octane but the additives in V Power and Chevron Premium with Techron to help reduce carbon build up on valves and combustion chamber. Carbon build up causes detonation and can be a bitch to remove once it builds up, last time I pulled the carb and looked at the intake valves they were spotless. In a mild climate regular should work ok in a 650 L.

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Haha... I tried putting some 110 octane in my 600... It hated it... so did the Xr70 , the xr250, the xr100, the lawnmower... I've learned to only run the 110 in my CR250

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