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clint_bazzill(at)hotmail.
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 Posted: Mon Jan 21, 2013 10:10 am Post subject: Rotax 912ULS ETC |
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Hi all,
I have been reading about problems with the Rotax 912ULS. I had some issues with this engine and will tell you what was done to solve this.
I attended the engine seminar at CPS in 1999, at that time Eric Tucker mentioned the starting kick of the 912S engine at that time, I didn't
know they had a 100 HP version and found it interesting. After the engine workshop I decided to sell my 912 UL and get the new engine, 25%
increase in HP with only a 3 lb weight gain seemed pretty good to me. I only had 360 hr on engine and found a buyer in our local chapter of EAA
in Half Moon Bay. Turned out to be my neighbor across the street.
After installing the engine it started up with no problem but as soon as I set it to idle it would load up, run rough and quit. I would empty the bowls
and the same thing would happen. I called Kerry at Lockwood and he thought the fuel pump was putting out too much pressure but before he sent me
a new one I borrowed the old fuel pump from my other engine and it did the same thing. I located another person who had a 912 ULS not Kitfox, he
had the same problem but he said it just went away. I thought there must be a vibration problem that was transferred to the carbs via the springs so
I removed them and the problem went away. I made a trip from Half Moon Bay to Tracy, Ca to see a friend and when I tried to start the engine, it kicked the
right carb off. I put it back on and it did the same thing, NOT GOOD. I got a ride back home and waited until traffic cleared and took my trailer and hauled
the Kitfox home. I ordered new springs for carb, cleaned the socket area and reinstalled the carbs. Then researched info on 912 engine, and found that
the pulse from the pickup was 20 degrees wide and on startup the engine would fire on the trailing edge of pulse which would put the timing at 6 deg BTDC.
After 1000 RPM's it would jump to 26 deg BTDC. The trick was to get the engine to that speed so it would run smooth, difficult with a high compression
engine. My solution was to pull the enrichment cable and crank the engine on idle for a full 10 seconds and then wait a full minute, open throttle 1 1/2 turns
on veneer throttle and the engine would start instantly running very smoothly. Since then I have modified the waiting time, depending on temp etc but it
works great. Also, on shut down I run engine to 2500 to 3000 RPM's, turn off ignitions and pull throttle back to idle, this allows the engine to spool down without
any kick backs etc. I believe that most of the gear wear on the gear box is during startup and shutdown by the high compression engine.
I believe Rotax recognized this problem and started installing slipper clutches in all their 912 ULS engines, they also put a new starter in that would turn the
engine faster on startup to get the engine turning faster.
I had a prop strike at about 700 hours and sent gearbox back to Lockwood for inspection. Kerry's comment was, "what ever you do with your engine keep doing it
as we see no wear". My final conclusion is, the 912 ULS has some issues when new on vibration on idle. Let it run with a higher RPM until the problem seems to
clear itself. Use a startup that eliminates the retarded timing.
I now have almost 1400 hours on this engine with 0 problems. It idles very smoothly and with static only adjustments. I usually idle about 1800 RPM's but it also
runs very smoothly at 1500. No problems on landing and always land with full idle. I installed this engine in my aircraft in 1999, and I believe it the first one in a Kitfox.
Clint Bazzill
Cameron Park, Calif
[quote][b]
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Lyle Persels
Joined: 10 Jan 2006
Posts: 34
Location: Osceola, IA
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| Posted: Mon Jan 21, 2013 10:32 am Post subject: Rotax 912ULS ETC |
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Thanks Clint.
With respect to the rough idle problem, I assume you're talking about removing the small (but stiff) retaining springs that attach the carb to the engine. I haven't had a problem with kickback on start on my 912ULS, but I haven't been able to correct the horrible idle.
Lyle Persels
On Jan 21, 2013, at 12:09 PM, Clint Bazzill wrote:
| Quote: | Hi all,
I have been reading about problems with the Rotax 912ULS. I had some issues with this engine and will tell you what was done to solve this.
I attended the engine seminar at CPS in 1999, at that time Eric Tucker mentioned the starting kick of the 912S engine at that time, I didn't
know they had a 100 HP version and found it interesting. After the engine workshop I decided to sell my 912 UL and get the new engine, 25%
increase in HP with only a 3 lb weight gain seemed pretty good to me. I only had 360 hr on engine and found a buyer in our local chapter of EAA
in Half Moon Bay. Turned out to be my neighbor across the street.
After installing the engine it started up with no problem but as soon as I set it to idle it would load up, run rough and quit. I would empty the bowls
and the same thing would happen. I called Kerry at Lockwood and he thought the fuel pump was putting out too much pressure but before he sent me
a new one I borrowed the old fuel pump from my other engine and it did the same thing. I located another person who had a 912 ULS not Kitfox, he
had the same problem but he said it just went away. I thought there must be a vibration problem that was transferred to the carbs via the springs so
I removed them and the problem went away. I made a trip from Half Moon Bay to Tracy, Ca to see a friend and when I tried to start the engine, it kicked the
right carb off. I put it back on and it did the same thing, NOT GOOD. I got a ride back home and waited until traffic cleared and took my trailer and hauled
the Kitfox home. I ordered new springs for carb, cleaned the socket area and reinstalled the carbs. Then researched info on 912 engine, and found that
the pulse from the pickup was 20 degrees wide and on startup the engine would fire on the trailing edge of pulse which would put the timing at 6 deg BTDC.
After 1000 RPM's it would jump to 26 deg BTDC. The trick was to get the engine to that speed so it would run smooth, difficult with a high compression
engine. My solution was to pull the enrichment cable and crank the engine on idle for a full 10 seconds and then wait a full minute, open throttle 1 1/2 turns
on veneer throttle and the engine would start instantly running very smoothly. Since then I have modified the waiting time, depending on temp etc but it
works great. Also, on shut down I run engine to 2500 to 3000 RPM's, turn off ignitions and pull throttle back to idle, this allows the engine to spool down without
any kick backs etc. I believe that most of the gear wear on the gear box is during startup and shutdown by the high compression engine.
I believe Rotax recognized this problem and started installing slipper clutches in all their 912 ULS engines, they also put a new starter in that would turn the
engine faster on startup to get the engine turning faster.
I had a prop strike at about 700 hours and sent gearbox back to Lockwood for inspection. Kerry's comment was, "what ever you do with your engine keep doing it
as we see no wear". My final conclusion is, the 912 ULS has some issues when new on vibration on idle. Let it run with a higher RPM until the problem seems to
clear itself. Use a startup that eliminates the retarded timing.
I now have almost 1400 hours on this engine with 0 problems. It idles very smoothly and with static only adjustments. I usually idle about 1800 RPM's but it also
runs very smoothly at 1500. No problems on landing and always land with full idle. I installed this engine in my aircraft in 1999, and I believe it the first one in a Kitfox.
Clint Bazzill
Cameron Park, Calif
| Quote: |
href="http://www.matronics.com/Navigator?Kitfox-List">http://www.matronics.com/Navigator?Kitfox-List
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[quote][b]
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Vic Baker
Joined: 11 Jan 2006
Posts: 71
Location: Carson City, Nevada
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| Posted: Mon Jan 21, 2013 12:55 pm Post subject: Rotax 912ULS ETC |
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Clint,
Good post.
Thanks,
Vic
Carson City
[quote] ---
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Vic Baker
Series 7
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dave
Joined: 22 Sep 2006
Posts: 1382
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| Posted: Mon Jan 21, 2013 5:07 pm Post subject: Rotax 912ULS ETC |
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well said Clint
[quote] ---
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