QuestionJohn, is there a great deal of difference and how important is it in a small engine like this?
When the heat rating is too low:
The spark plug temperature rises too high and induces abnormal combustion (pre-ignition): this leads to melting of the spark plug electrodes as well as piston seizure and erosion.
NGK Spark Plugs pioneered the use of a copper cored electrode in 1958, which enables a spark plug to heat up quickly and also dissipate heat quickly giving an ultra wide heat range. It is essential to use a spark plug that fits a specific engine and its conditions of use.
As spark plugs are positioned in the head of an engine, their analysis can give a good indication of how your engine is operating.
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The text above is a follow-up to ...
-----Question-----
John, on my Sears 6.75hp mower #917.378420 I was wondering if I could substitute the Champion spark plug RJ19LM (#35395) for
a J17LM (#33636)
I also am at an altitude of 6500 ft and was wondering if running the mix leaner would help.
-----Answer-----
Hello Colorado:
The Only Difference is the J17LM is a Colder Plug and Isnt a Resister Plug like the RJ19LM. Yes for the Higher Altitudes you can Lean the Mixture to Umprove Performance. Hope this Helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks. Be Safe.
Good Luck
Respectfully
John
Answer Hello Colorado:
When Talking Automotive Engines you are Correct. With the Small Engines the Plug can be Either 1 Stage Cooler or 1 Stage Hotter and there is Little Noticable Effect on the Engine. If you were to ask About Using a J15LM in Place of the RJ19LM then I would Suggest you Try a Different OEM and Stay as Close to the RJ19LM as Possible. A J15LM or RJ15LM is Too Cool for the Engine. You can Safely use a RJ17LM, J17LM, RJ21LM or J21LM in the Mower Engine. I would Not Suggest this for Automobiles though. Remember the Application of the Plug is Different than in Automobiles. Hope this Helps. I am here if you Require more Assistance. Thanks. Be Safe.
Good Luck
Respectfully
John
