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So I have a 2013 grizzly 550, bought it brand new and has 3600 miles on it. It’s a great machine, only problem so far the rectifier went bad and normal wear and tear, new axles and tires, and regular maintenance. This past time on the trail, it started running rough like starving for fuel or something. I read somewhere that the gasoline loses octane when it gets hot. I opened the cap at the time, and was like a heater was on in there. I had plenty of fuel, and when I got home rode a around for a while no issues. I’ve always put a oil change kit which includes spark plug oil, filter, and air filter. Any suggestions?
 

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Octane retards combustion under compression so that is probably not your problem. I run 85 octane with corn here just fine.
If you are riding slow when this happens, use low gear to let the engine run faster to move more coolant through the engine.
I have a different bike with different tank placement, and when I started seeing bubbles in/on the bottom of the tank when very hot, I did a few things and the problem is gone.
1) Use low gear as mentioned above..
2) I added metal tubing to the upper radiator hose to let heat escape the system, like a coolio found here...I am cheap and used cooper tubing :)
https://www.amazon.com/G2-Ergonomics-70-130-Coolio-Line/dp/B000K7MTR0
3) On the 660 the stock air intake snorkel is under the tank cover where heat can be trapped, so I drilled several extra holes in the air box lid so air is pulled from under the seat nit the tank cover.

and I noticed this boiling happened more when the tank was down, say 1/2 or more, so try keeping the tank closer to full.
 
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