06-06-2012, 03:14 PM #1
Ultra 250X/260X/300X Spark Plug Torque
Use a torque wrench and tighten to the factory torque spec when installing spark plugs on your Ultras.
Not only the properly torqued plugs would come out easier later, but also they ensure the peak performance of your Ultra’s engine. Over-torqued plugs are more likely to develop an internal crack causing intermittent "no-spark" condition. Have you ever heard or experienced Ultra 250/260/300 suddenly running poorly, and then runs better right after replacing the plugs? And then, you wonder, “Why does Ultra go through plugs like 2-strokes?” That’s because one or more of your spark plugs have the internal crack and they are not firing.
Through the crack in the spark plugs center core ceramic insulator, the current will find an easier route (with less resistance) to find the ground, instead of trying to jump the ground electrode gap. When that happens, you are running on either 3 cylinders only or less.
Supercharged engine's peak combustion pressure is approximately 56% higher than that of the same N/A engine. More fuel/air in the same volume combustion chamber (1498 cc, same as 15F) means higher combustion pressure even though compression ratio is substantially less, Ultras 7.8 (250/260), 8.4 (300) vs. 15F’s N/A 10.6. The NGK PMR9B spark plug for Ultras is specifically designed for such high combustion pressure engines against the possible internal cracking. That's when the proper plug installation torque becomes critical - you don't want to induce any unnecessary stress on the plugs by over-tightening them. According to NGK, only 2 vehicle manufacturers use the PRB9B plugs. Kawi (on their Ultras) and Maserati's first gen supercharged 405 HP 4.2L V8 Gran Turismo in 2007 (now 4.7L making 440 HP) , Quattroporte, etc. Do yourself a favor and use a torque wrench on plugs next time. After all, it's your ski.
11-25-2012, 07:42 PM #2
Great advice about over-tightening. I learned this the hard way yesterday winterizing my 15F and getting lazy/stupid by not checking the manual and snapping the last one after fogging. 5 years winterizing this ski I should have known better. I'm going to re-torque 3 others as I don't want any "intermittent no-spark conditions" as you mention in your write-up. Thanks again for the great advice.
12-21-2013, 12:48 AM #3
12-21-2013, 02:00 PM #4
Is that torque spec for wet or dry installation? It's important to remember that there are two ways to measure plug tightness: torque, and rotation after initial seating. The second method must NEVER be used if you are re-using the gasket. New gaskets are always recommended.
12-21-2013, 06:45 PM #5
01-17-2015, 06:02 PM #6
- Join Date
- Jul 2013
Do you guys add anti seize on your plugs?
01-17-2015, 06:35 PM #7
Yep ,I believe most do,there's mixed feelings whether to torque to specs do to anti seize application making reading possibly inaccurate or just hand tighten and then some (1/4 more)
I anti seize then hand tighten then tighten down to specs 9.6 ft-lbs..
Last edited by jetdave56; 01-17-2015 at 08:56 PM.
01-17-2015, 07:14 PM #8
- Join Date
- Aug 2011
- Australia Melbourne
08-30-2015, 07:20 AM #9
I put in new plugs in my 300x maybe 8 hrs ago, all is good I torqued them to spec 13Nm, but my question is can I remove them to add some anti seize, and then put them back in? or will the ring gasket at the bottom the spark plug become ineffective if torqued twice? Also I ride in fresh water only. Do I need anti seize? Anyways just a copper coat type anti seize will do?
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