OPJOSE,

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You raise an important fact. I have 3 OS engines and I use the same fuel and flew all 3 the same amount of time.</p>

However only one (the LA) has a lot of stains and that stain is mostly on the top of the cylinder.</p>

And that engine beeing an LA has a metallic rattling sound since the first time I started it.</p>

The hobby shop told me it was OK, and that all LA engines have this noise.</p>

I am not a handy person and I know very little about engines, I would not try to uncrew the head myself.</p>

I will ask a friend for help.</p>

Thanks,</p>

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