I am having problems with the left magneto on my Jabiru 3300 engine. When I conduct the mag checks there is almost no rpm drop on the right mag. However, when I check the left magneto the drop is 200-250 rpms and the engine runs very roughly.

My A&P suggested installing new spark plugs. I did this, but it did not help. So, a friend suggested replacing the rotor and distributor cap. If the doesn't solve the problem, he recommended installing a new magneto.]

Any thoughts on the best strategy to pursue now?

Also, if I need to buy a rotor, distributor cap, or magneto, any places in the U.S. that sell them?

Thanks in advance for your help.

Gene

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Support and all parts should be available from the US Jabiru distributor, Arion Aircraft : www.flylightning.net.

John

N750A

Thanks John. I will contact them on Monday!

Best regards,

Gene

Don't know if this would help but did you check and set the clearances of the magnets and the coils? This would be a good place to start and it's easy to do.. I bought some brass shimstock that measures .010 and cut out strips large enough to place between the coil and magnets. Clean any rust off of the flywheel magnets gently. Turn the prop to align coil and magnets up, insert the shimstock, loosen the coil screws and the magnet will pull things together, tighten screws then remove the shimstock. You may find it difficult to remove the brass shimstock if there was any rust not cleaned prior. You might need to rotate the prop a little to remove the shimstock but now you know you have the minimum clearances called for by Jabiru..

  As far as my memory of checking coils for the proper resistances OHMs, they are given in the Jabiru engine manual. 

Another thought is if the weak side occurs when engine is hot vs being fine at cold start up. This would indicate a coil issue. Check your distributor caps and rotors for pitting and burning. Aluminum is used for the contacts in the caps. This burns away quickly. On my 2200 Jabiru I found and installed a distributor caps and rotors that had brass contacts from an automotive application that I purchased from a local NAPA store. Even used suppression core wires and NGK Iridium spark plugs. These plug lasted a long time.

All modifications with good results as I could idle it down to 300 to 400 rpm and you could not feel any vibration and was very quiet.

So, in summation. It could be a defective coil or output wire, coil clearances to magnet, pitted distributor caps creating excessive cap to rotor clearances. I eventually sold my plane, but I loved to work on and improve the Jabiru engine...

Don's advice is spot-on!  Also be sure that you have cooling air diverted to the coils.  You need ducts about 1/2" min. i.d. coming off the ram-air ducts and aimed at the coils - it's covered in the FWF installation manuals that I "think" are still available on-line, as are the factory Jabiru maintenance manuals.

In the above pic you can see the white PVC duct coming off the ram-air duct.

John

Dear John:

Thanks again. I will check the Jabiru manual for the proper clearance.

Best regards,

Gene

Dear Don:

Thanks for your recommendation, it's much appreciated. . I will give it a try before doing anything else.

Best regards,

Gene

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