Forum Tech Talk Engine "Flutter"

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Engine "Flutter"

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Dan Myers
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Joined: Tue Feb 18, 2014 12:53 pm
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I'm pretty much out of ideas on this issue and it's a bit of a strange one. Curious to see what some other thoughts are out there.

When at high RPM and minimal throttle, the bike will have a very audible "flutter" sound. It does not do it at low RPM and it does not do it at high RPM with the throttle greater than 15 - 20%. You can most noticeably hear it in this video ( at the 15:57 mark. I let off at high RPM and then get back on it minimally and it has this "flutter". It does it again even more noticeably at 18:28.

In response to it, I tend to short shift a bit and it does not do it.

What I've done thus far:
1 - At first I thought it was possibly leaning out on the top end with the Lectron carb so i richened up the power jet and it had no effect.
2 - I then thought it could be the reeds starting to thin and "fluttering" inconsistently with the engine. I put in brand new Boyeson super stock reeds, which had no effect.
3 - lastly, I thought it could be something to do with the power valves. Maybe gunked up or something loose. Checked them and they were very clean and in good mechanical shape.
4 - Note: I've checked the compression a few different times and it's at 150psi.
5 - Recently rode the Moose Run and it had the flutter, but showed no signs of not being able to complete the race outside of two flat tires.

Any other ideas?

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