Spark Plug Numbers

Discussion in 'Mechanic and Repair' started by mmacsek, Feb 16, 2006.

  1. mmacsek

    mmacsek LawnSite Senior Member
    Posts: 544

    I'm in the process of getting a spark plug order together for the season. My question is alot of the plugs on the 2 cycle, same manuf., have an R in the number which means resistor. The plugs I want to order have the same number minus the R. Will this affect the performance not having a resistor plug? Also, the number is the heat range..... If the number is 8 and I use a 7, what happens? Thanks Matt
     
  2. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Posts: 3,504

    If you wear some type of radio or mp3 player while you mow, the non R (resistor) plug will cause alot of interference. I think a colder plug (7) may cause the motor to gum up some. Usually a hotter plug is used to burn the oil mix. Maybe Rob will chime in or some one else.

    wayne
     
  3. Jman

    Jman LawnSite Member
    Posts: 217

    Not only could it effect noise in your own radios, but possibly interfer with customers wireless high speed routers and other items in and around the home. There is a reason the engine manufacturers want the certain number, for the heat range. Don't change from the recommended to save a quick nickel. The engine failure that could result may be MUCH more expensive.
     
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Some plug manufacturers rate their numbers back-wards NGK for one the lower the number the hotter the plug. As stated above it's best to stick with the OEM plug number.
     
  5. mmacsek

    mmacsek LawnSite Senior Member
    Posts: 544

    Thanks guys. I was planning on using the same heat range. Some ramble... In the past I bought on an as needed basis but that gets costly in more ways than one. I am setting up a parts inventory for equipment. It seems that every year the spark plug #'s change so keeping the same brand of equipment doesn't keep it simple. Thanks again guys. Matt
     
  6. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Posts: 3,504

    I learned something new today, I used to deal with A/C plugs and the higher the number the hotter. On some of the newer engines with no adjustments I play around with heat ranges. Just with NGK's Ive been doing it backwards hammer :dizzy:

    wayne
     
  7. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Don't feel bad Wayne, I did the same thing when I left the automotive field. The only reason I stumbled across it is we didn't have the exact plug for a unit so I went to the catalog to find out what all the letters meant.
     

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