Rotax question

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Rotax question

Postby scubarider2 » Sun Jun 29, 2014 6:30 pm

Ok Rotax or carb gurus...did a synch on the carbs today. Have a CarbMate. Hooked it to the battery, dialed in the green dot, cranked the engine, adjusted one carb (pilot side) at 2500rpms, got it right on, adjusted the gain all the way up and continued to adjust the carb until hit it in the green all the way. Then lowered the rpms back to 2000 all good, then up to 3500 and back off the green, back down to 2500 on the green. So my question is this. Is it normal when doing a synch that changing the rpms will change the synch? Any advice?
Thanks,
Dennis
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Re: Rotax question

Postby kenryan » Sun Jun 29, 2014 7:44 pm

According to rotax-owner.com instructional video http://www.rotax-owner.com/videos-topmenu/elearning-videos/46-carb-synch20 the carbs should remain synchronized throughout rpm range. If they don't possible problems suggested are cable binding or uneven cable length.
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Re: Rotax question

Postby gkremers » Sun Jun 29, 2014 7:55 pm

Dennis,
I don't claim to be a Rotax guru but have had them in two planes. I have never been able to get them "perfect" through all RPM ranges. Very close but not exact. I also have the Carb mate with the Rotax hose package and used it the first time I synced the carbs. I guess I'm old fashion because I'm going to sell it after only one use. Not that it didn't work, I just like seeing exactly what is going on. I bought dual vacuum gauges, for me it was much easier to "see" exactly what was going on. Try to get the carbs perfect at idle, and 2500 RPMs. Not sure what prop you have but if it's ground adjustable the closer you can get the blades at the same angle the better. On my Whirlwind 3 blade I get them within .01 degree, it makes a world of difference, much smoother.

Good luck
Gary
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Re: Rotax question

Postby scubarider2 » Wed Jul 02, 2014 4:36 pm

Thanks guys. I thought of both the cable and the prop. I checked the prop and it is as close as I can get it. I have a Warp 3-blade 72in. I checked the cables for the carbs and they seem to pull the same checking both full throttle and closed. I got it through the rpms pretty close. And the engine seems to run pretty smooth. So, hopefully all is good. :wink:
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