Syncing the carbs is one of the most satisfying aspects of the annual condition inspection — or the most frustrating.
When I took my Repairman course the instructor showed us how to use the CarbMate tool to pneumatically synchronize the carbs. That looked pretty cool, so I bought a CarbMate. Bad decision. The fittings that it came with were US automotive dimensions and the Rotax carb tubing is metric. I had to make adapters. After working with it I found the moving LED lights hard to interpret and confusing and had to school myself each time I used the tool to relearn how it worked. Syncing took a long time. The CarbMate went on the auction site as a motorcycle sync tool. Hopefully another Rotax mechanic didn’t buy it.
Then I bought a pair of gauges advertised as for the Rotax. These worked better and were a bit easier to interpret but the needles were very jumpy due to intake pulses and the little valves did not take out all the pulsations. Whenever the rpm was changed even slightly the anti-pulsation valves had to be adjusted.
I rewatched the Rotax-Owner video and the manifold pressure gauge that they were using looked like a much better solution. I was able to find a twin engine aircraft gauge for about $100, about the same as a gauge set cost.
This works really well. I have the tubing set up so the left and right carbs are on the left and right needles (naturally!)
I intentionally sought out a gauge that was made for normally aspirated engines so the maximum reading is 35 inches. I figured this would give the most resolution on the scale for the purpose of carb syncing.
The needles are internally damped so they don’t bounce around and there is no fiddling with valves to damp them out.
The procedure I use is to hook up the gauge on the starboard side and place it on the passenger seat. Then I get in and lock the canopy in the hold open position, start the engine and make a reading. Then shut off the engine and make a carb cable adjustment. Real easy to interpret what is happening. Only takes a few tries to get the needles right on top of each other. This makes syncing the carbs actually fun!
(Don, using a caliper to mechanically set the linkage won't work!)
When I took my Repairman course the instructor showed us how to use the CarbMate tool to pneumatically synchronize the carbs. That looked pretty cool, so I bought a CarbMate. Bad decision. The fittings that it came with were US automotive dimensions and the Rotax carb tubing is metric. I had to make adapters. After working with it I found the moving LED lights hard to interpret and confusing and had to school myself each time I used the tool to relearn how it worked. Syncing took a long time. The CarbMate went on the auction site as a motorcycle sync tool. Hopefully another Rotax mechanic didn’t buy it.
Then I bought a pair of gauges advertised as for the Rotax. These worked better and were a bit easier to interpret but the needles were very jumpy due to intake pulses and the little valves did not take out all the pulsations. Whenever the rpm was changed even slightly the anti-pulsation valves had to be adjusted.
I rewatched the Rotax-Owner video and the manifold pressure gauge that they were using looked like a much better solution. I was able to find a twin engine aircraft gauge for about $100, about the same as a gauge set cost.
This works really well. I have the tubing set up so the left and right carbs are on the left and right needles (naturally!)
I intentionally sought out a gauge that was made for normally aspirated engines so the maximum reading is 35 inches. I figured this would give the most resolution on the scale for the purpose of carb syncing.
The needles are internally damped so they don’t bounce around and there is no fiddling with valves to damp them out.
The procedure I use is to hook up the gauge on the starboard side and place it on the passenger seat. Then I get in and lock the canopy in the hold open position, start the engine and make a reading. Then shut off the engine and make a carb cable adjustment. Real easy to interpret what is happening. Only takes a few tries to get the needles right on top of each other. This makes syncing the carbs actually fun!
(Don, using a caliper to mechanically set the linkage won't work!)
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