 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
henryroden
Joined: 09 Jan 2006
Posts: 13
Location: Albuquerque
|
 Posted: Tue Jul 09, 2013 7:43 pm Post subject: Large mag drop |
 |
|
I have a 912ULS in a RV-12, the plane has just been signed off by the DAR but I have not yet flown it. The engine starts fine right away and has about 2 hours of taxi time on the engine. I get 5050 rpm at wide open throttle and the airport is at ~5000'. The weather here is in the 90+range shortly after 9:00 am. The problem I am having, which has kept me on the ground, is the mag drop. It is about 650 rpm on each ignition and they both run rough. They are close together but that much of a rpm drop seems very unusual. The exhaust pipe is sooted which suggests it is running rich. The plugs also are very black and cleaning them has no effect. All the other temperatures look normal. I tried a five minute run at full throttle and that had no effect either. Any ideas where to look next will be greatly appreciated.
Thanks
Henry
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
|
|
| Back to top |
|
 |
Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
|
| Posted: Tue Jul 09, 2013 10:05 pm Post subject: Re: Large mag drop |
|
|
Hi Henry,
650 is way to high. The good thing is they are almost equal. What rpm are you doing the mag drop at?
What is the plug gap? It should be between .023 and .027. Better to be the wider gap for the summer months. Are you running an electric pump with the mechanical all the time? Have you synced these carbs? Did you put a fuel
re-circulation line in during the build. The new pumps really need one. Where did you mount the carb vent tubes? These carbs almost sound like they are flooding, but we could use a little more info.
It is possible you have a wire connected wrong.
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
|
| Back to top |
|
|
conrad
Joined: 07 Feb 2007
Posts: 16
Location: Banbury. UK
|
| Posted: Tue Jul 09, 2013 11:24 pm Post subject: Re: Large mag drop |
|
|
Looks like you might have a couple of plug caps swapped.
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
|
|
| Back to top |
|
|
henryroden
Joined: 09 Jan 2006
Posts: 13
Location: Albuquerque
|
| Posted: Wed Jul 10, 2013 5:51 am Post subject: Re: Large mag drop |
|
|
Hi Roger,
By a wire wrong I ASSume that you mean a plug wire? I will check that but it is the same as it came from Van's. The mag check was done at 4000 rpm both before the run at 5000+rpm and after that too. No change.
The plug gap is at 0.020", I will open them up to 0.028". There is an electric pump just after the fuel tank and I have run with that on, usually about 5 psi is shown on the fuel pressure gauge. There is a fuel return line to the tank.
The vent tubes come down to the drip tray. Every thing indicates flooding or a very rich mixture. With a lycorasuras I would run it close to wide open and lean it out very aggressively but can't or don't know how to do that with the Bings. I have done a mechanical sync. but not yet done a pneumatic sync.
I ASSume that the two ignition systems, A & B, each control one set of plugs, upper and lower although I have not yet found in the documentation which one is the upper plugs and which is the lower plugs.
Do you make house calls? 
Thanks
Henry, Los Lunas, NM
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
|
|
| Back to top |
|
|
Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
|
| Posted: Wed Jul 10, 2013 8:20 am Post subject: Re: Large mag drop |
|
|
Hi Henry,
The plug gap is way to small. The Rotax specs are .023 (cold weather and .027 hot weather) Do not gap them wider. This will change the mag drop all by itself. Then as Conrad suggest look at the plug wires. The wires are labeled. #1 cyl. is front right, #3 is rear right, #2 is front left and #4 is rear left. Try not running the electric pump. You may be flooding. You absolutely need to do a pneumatic sync. All a mechanical sync does is get you in the ballpark for idle and hopefully close for higher rpm runs, but it can be significantly off. Do all of these things first before the next start.
The ignition system chart you are referring to is in the Heavy Maint. manual.
After you do these couple of things then try a new mag drop and let us know the results.
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
|
_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
