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It could be just that batch of fuel. What's the batch number? The same thing happened to my YS .63 when I switched to a new gallon of Powermaster YS 20/20. The engine ran fine on the previous gallon. However, it started detonating when I began using the new gallon. The knocking noise was so bad that I had to run the engine richer than usual.
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There are a lot of people running 30% nitro in their YS 4-strokes without any problems. I suspect your LHS may store their fuel on a concrete floor. That, and give the fact that your fuel has an older batch number indicates that water may have found it's way into the can which can cause all kinds of problems even if the fuel does not appear milky. Been there, done that.
John
John
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mpj220
Mark have had no complaints on the batch 2549 25/20 fuel which is a pattern fuel. The batch is over two years old and during this time have had no reports of any problems when using this fuel.
It sounds like the engines are pre-det. causing them to run hot. This fuel is an all synthetic oil mix the same as the 20/20 fuel, just more nitro.
Will pull retain and check to see if there is/was a problem in the mix.
Wendell
Mark have had no complaints on the batch 2549 25/20 fuel which is a pattern fuel. The batch is over two years old and during this time have had no reports of any problems when using this fuel.
It sounds like the engines are pre-det. causing them to run hot. This fuel is an all synthetic oil mix the same as the 20/20 fuel, just more nitro.
Will pull retain and check to see if there is/was a problem in the mix.
Wendell