New spark plug gap

Look at the drawing of the spark plug in the Old LMM and the drawing in the New one.

They are two different spark pug designs.

The Old single electrode plug has been replaced by the newer dual, non-adjustable electrode spark plugs.

You can't compare Oranges to Grapefruits.  

The next question, of course, is: "Why does new line maintenance manual specify new spark plugs?" 

NGK told Rotax that it no longer wants to be associated with airplanes. Rotax responded by going to a whole different (expensive) spark plug. The NGK plugs still work and there are still two of them per cylinder for reliability.

Yes, I guess NGK is somehow worried about liability, but why does Rotax (or anyone) have to acquiesce to the wishes of the manufacturer of something that is freely sold and available to anyone?  

Is Rotax actually making the new ones in house?  Is there some special patent on the old plugs?  Perhaps some legal minds can weigh in on all this...

Tyler asked:

...   why does Rotax (or anyone) have to acquiesce to the wishes of the manufacturer of something that is freely sold and available to anyone?

NGK is free to sell or withhold its products from anyone it wishes.

When the Rotax purchasing agent wanted a thousand spark plugs, I am sure that they bought them directly from NGK at wholesale prices.

Now that NGK is refusing the sale, their option would either to find another manufacturer or go under the table and deplete the stock of 50 auto parts stores and pay retail prices or find a retail distributor and make a bulk purchase.

When NGK sees their retail distributor suddenly selling 5 times the normal amount of one very specific plug, they smell a rat and threaten to cut off the distributor from all products unless they stop supplying Rotax under the table.

Thousands of engine owners all over the world buying 8 plugs a year is something they can't control and is still an option for everyone.

So a new plug was designed and branded ROTAX with all the liability now transferred to Rotax.

The new plug might very well still be produced by NGK, but as long as their name is not on the body, they are happy because the testing, acceptance, and certification is now on Rotax.

Corporate politics at its finest!!!