The best 20 buck I ever spent

[Texasautogyro]

I had just finished a 100 hr on the MTO. The gyro looked great! But when I flew up to Bridgeport it seemed to run a little hot. The 912 was on the top of the green instead of bottom. I also seemed to be a little down on power. I tried to up the octane and ran a little 100LL but saw little change. When we got back to Tomball I put in a new set of plugs. The old ones still looked great. When I took it out the power went up about 15% and the temp never got above the bottom of the green. Well worth the few bucks to invest.

[CLS447]

For 20 bucks you did not get the Iridium ones. I got a set of them to go in next.

[Texasautogyro]

I just took one out and matched it from Rotax. They have them at any auto parts place. About 3 bucks retail or 2 my cost.

[All_In]

At that price I would just change them out at every 100 hour inspection.
Thanks for sharing your experience.

[okikuma]

Good catch Desmon.

A gap that is too wide might prevent a spark from firing at all or may missfire at high RPMs. A gap that is too narrow often gives a small and weak a spark to effectively ignite the complete fuel-air mixture and have symptoms of running too rich. A spark which intermittently fails to ignite the fuel-air mixture may not be noticeable directly, but will show up as a reduction in the engine's power.

When I change and gap new spark plugs for my car, I always gap at the lowest manufacture recommended gap setting. That way, the plugs last longer between changes.

As for your aircraft engine, always follow the manufacture's recommended gap settings.

Wayne

[CLS447]

Here are the Iridiums........http://www.ngksparkplugs.com/product.../iridiumix.asp

About 6 bucks apiece. Doesn't Rotax say every 25 hrs ?

[JEFF TIPTON]

900 Series. Rotax recommends cleaning at 100 hours and replace at 200 hours. At shop rates it is cheaper to replace them each 100 hours.

[digbar]

Rotax recommends a 25-hour interval for plugs in 2-stroke engines, that have to put up with firing every 360 degrees and the oil/gas mix. Gapping car plugs .002 closer than minimum yields a little power increase, as well as making the plug stay in spec longer; this from a PhD who wrote a book about ignition systems. I do it in my rides and motorcycles.

[Mike G]

Desmon
So what plugs did you use? Makers name and reference please
Mike G