carb piston "apertures"
in 912 / 914 Technical Questions
4 years ago
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by Tyler Hathaway » 4 years ago
Roger Lee wrote:
I never thought someone would put a different piston in a carb. I was thinking original piston.
The thing is, those ARE the original pistons. I have owned this engine since new. This is only the second time the carbs have been apart. The first time was at the 200-hour inspection, and I was with the guy when he did that (and replaced the circlips), but neither of us noticed this difference at that time. But I know for sure he didn't slip some other piston in there on me, haha.
The other thing is, both pistons have identical stampings on them. If it were a piston for another application, I assume it would be marked as such.
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by Rotax Wizard » 4 years ago
Roger, look at the size of the flat beside the arc...thats the problem. The 2 are not the same.
Cheers
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by Rotax-Owner » 4 years ago
Tyler
The biggest question we all have is... HOW did It run/idle? Did you experience any vibration, issues with carb balance, get full RPM?
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by Tyler Hathaway » 4 years ago
One of the reasons I was anxious to do the inspection was I did recently start geting a noticeable vibration at idle, and my #4 EGTs were always lagging the rest, up to about 2300rpm. Higher than 2300 and it all seemed fine. But probably once the piston rises, in the midrange, the difference in aperture is less of an issue. Of course I was going to do a complete sync after the inspection, but for the moment I'm stopped in my tracks.
I did not have any trouble getting a pneumatic balance at around 2700 rpm when I last did it, 100 hours ago.
Additionally, I could never get much more than 5500 at WOT (usually less than that on actual takeoff), but I was thinking that had more to do with my propeller pitch...
What typically happens after submitting a CSIR? I got an auto-acknowledgement that it had been received, but that's all, so far.
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by Rotax-Owner » 4 years ago
Interesting. WIth different shaped carb slides, I would imaging it being an issue at lower RPM as you said. The CSIR will be sent to the Rotax Factory and they will have a record of what was found on your engine. You won't hear anything back from Rotax.
The 5500 WOT is most likely due to your propeller pitch.
Thank you said by: Tyler Hathaway
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