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GedR
23-07-19, 07:21 AM
Does anybody know of a video demonstrating how to balance 912 carbs? I know there is one at the Rotax Owners Club but it is 29 dollars to look at it! Thanks for your help
Ged

Rodent
23-07-19, 07:50 AM
www.999tom.com/documents/pilotdocs/Rotax912Maintenance.pdf

Antoni
23-07-19, 07:54 AM
Are the carb rubbers completely sound ‽ ‽

If you have reason to believe the carbs are out of balance there's an old quick and easy method that doesen't need carb balancing vacuum gauges. It's not ideal but better than nothing.

Check whether both throttle cables at the carbs begin to open the carb butterflies equally when the engine is not running. If so, or nearly so leave them alone. Take the air filters off.

With the throttle cables slack (there must be some slack when the controls are closed), get a piece of fuel pipe, start the engine warm up a bit and run at idle. Place one end of the pipe close to your ear and offer the other end to the lower part of the carb's intake. The loudness of the sound should be similar. The louder one is doing more work than the quieter one.
Consider adjusting the idle stop screws.

Get someone to apply a tiny bit of throttle. Consider adjusting one or other of the throttle cable adjusters so that the sound is similar because both carbs are opening together.

The reason you shouldn't just check that the carbs begin to open equally when the engine is stopped is because of 'cable stiction'. The vibration of the engine when running will jiggle the cables into their natural comfortable positions, and the sound from the carbs is more accurate than looking at cable movements.

If anyone thinks this is dangerous crap please feel free to say so, I won't be offended!

Gentreau
23-07-19, 09:49 AM
.........If anyone thinks this is dangerous crap please feel free to say so, I won't be offended!

I must admit that doing anything close to the engine when the prop is spinning sounds dangerous ...

goldrush
23-07-19, 17:36 PM
I must admit that doing anything close to the engine when the prop is spinning sounds dangerous ...

Have been doing this for some 70 Years on motorbikes, racing cars and aircraft ( I am now 83 and still alive) the length of the tube does NOT need to so short that your head is too close to the prop (*But as always rotating PROPS WILL bite fools!), although it is more difficult to distinguish the change with a long tube.... or maybe it's my hearing... should have gone to Specsavers?!!!!!!!!
Just rapidly putting the open end to each carb in turn makes this difference more obvious.

jetlag
23-07-19, 19:01 PM
One can even buy cheap stethescopes these days. Used the pipe on motorbikes to good end results in my younger days
https://www.amazon.co.uk/Universal-UN125B-Single-Stethoscopes-Individually/dp/B018P90JH6/ref=sr_1_5?keywords=stethescopes&qid=1563904756&s=gateway&sr=8-5 (https://www.amazon.co.uk/Universal-UN125B-Single-Stethoscopes-Individually/dp/B018P90JH6/ref=sr_1_5?keywords=stethescopes&qid=1563904756&s=gateway&sr=8-5)

Dave Morton
24-07-19, 07:31 AM
Skydrive (they're still selling items) have a balancing kit that is extremely accurate and easy to use with LED's to indicate correct balancing, our club purchased one and all the rotax's are running sweet...