Rotax 912ULS Starting problems.
Moderators: John Dean, Moderator
Rotax 912ULS Starting problems.
I own a Foxbat A22 with a Rotax 912ULS, over the last year I have had numerous problems starting it from cold and sometimes when warm. Once running the engine would run perfectly. I have had 1800 hours flying with a Rotax 912 so I know the proper techniques for starting. The engine would eventually start after lots of cranking but run quite rough for the first half minute or so and then start running smoothly. Having been up many blind alleys with carburettor set up and float levels etc I eventually discovered that the problem was with the SMD modules, changing these at enormous cost of £900 the problem has been resolved. The reason for writing this post is so that other people with a similar problem may get in touch as after there is an obvious problem with SMD from certain years failing. My engine is from 2005 no:5644872.
Re: Rotax 912ULS Starting problems.
For what it,s worth, we have just been through a similar saga with our 912s, with a succession of starting difficulties.
Following the line of eliminating the most likely culprits first, we purged the fuel lines, float bowls and filters. We then sent the carbs off for their scheduled service (admittedly some 40 hrs in advance of schedule), and balanced the carbs (twice). During this time we also checked out the electrics for spark strength, and replaced the plugs despite only having 45 hrs on them.
The fault was accurately diagnosed after lengthy discussion with Simon at Eccleston Aviation as being the onset of a sprag clutch failure. Being a Grade 1 sceptic, I was not convinced that a component which should engage the starter and restrict kick back would have any effect on the starting problems we were having, however we bit the bullet and had the sprag clutch replaced. The upshot of this.......she now purrs like the proverbial feline on start up and shut down.
The moral of this tale....the engines are complicated beasts, and a phone call to a reputable professional can often point you down the correct path before you commit to unnecessary expense (as we did.....oops).
Following the line of eliminating the most likely culprits first, we purged the fuel lines, float bowls and filters. We then sent the carbs off for their scheduled service (admittedly some 40 hrs in advance of schedule), and balanced the carbs (twice). During this time we also checked out the electrics for spark strength, and replaced the plugs despite only having 45 hrs on them.
The fault was accurately diagnosed after lengthy discussion with Simon at Eccleston Aviation as being the onset of a sprag clutch failure. Being a Grade 1 sceptic, I was not convinced that a component which should engage the starter and restrict kick back would have any effect on the starting problems we were having, however we bit the bullet and had the sprag clutch replaced. The upshot of this.......she now purrs like the proverbial feline on start up and shut down.
The moral of this tale....the engines are complicated beasts, and a phone call to a reputable professional can often point you down the correct path before you commit to unnecessary expense (as we did.....oops).
Alan Paterson
037243
037243