Correct Spark Plugs Pony Motor D7E 48A?

Sparkplug 9M4141 still available from Caterpillar in Texas anyway.
Craig

Try an Autolite 86 or a NGK BP4.
A resistor type plug is not recommended for magneto ignition.
9M4141 is the Cat number for the Champion J18YC but no telling what it supersedes to now.

The current sparkplug from Caterpillar is a Champion RJ18YC. I wonder if Caterpillar decided that the design of the RJ18YC resistor sparkplug was not detrimental to magnetos or if Caterpillar just didn't care. I hope it is the former.
Craig

Good article here....basically any resistance causes the mag to work harder and produce less.
http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magnetos%20generally/Are%20suppressors%20and%20resistor%20sparking%20plugs%20OK%20to%20use%20with%20magnetos.htm

Good article here....basically any resistance causes the mag to work harder and produce less.
http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magnetos%20generally/Are%20suppressors%20and%20resistor%20sparking%20plugs%20OK%20to%20use%20with%20magnetos.htm

That is an interesting article O.M, Thank You! I found an interesting aviation article that some of you may find interesting as well. General aviation aircraft have and are still running magnetos. Looks like Champion had some growing pains with regards to aircraft high resistor spark plugs.

I called Cat and the parts gentleman said my Cat takes a 8F5899 spark plug, he said it did not supersede to another number. He did not know if they were or were not resistor plugs. It goes without saying that some parts people are more informed than others. Cat Pony motors and low resistant spark plugs seem to pre-date the invention of the wheel when I speak to some of newer parts professionals. One magneto professional explained that the coils in magnetos are generally smaller and really not designed for use with high resistance plugs, he also agreed with O.E. article that your spark will be diminished and the coil will have to work harder if using modern high resistance plugs. He said for the short time a pony is running you may be fine, but use non resistant plugs if you can.

Here is the link to the Aviation Magneto Article I found interesting:

http://blog.aopa.org/opinionleaders/2015/03/19/champion-from-denial-to-acceptance/

That is an interesting article O.M, Thank You! I found an interesting aviation article that some of you may find interesting as well. General aviation aircraft have and are still running magnetos. Looks like Champion had some growing pains with regards to aircraft high resistor spark plugs.

I called Cat and the parts gentleman said my Cat takes a 8F5899 spark plug, he said it did not supersede to another number. He did not know if they were or were not resistor plugs. It goes without saying that some parts people are more informed than others. Cat Pony motors and low resistant spark plugs seem to pre-date the invention of the wheel when I speak to some of newer parts professionals. One magneto professional explained that the coils in magnetos are generally smaller and really not designed for use with high resistance plugs, he also agreed with O.E. article that your spark will be diminished and the coil will have to work harder if using modern high resistance plugs. He said for the short time a pony is running you may be fine, but use non resistant plugs if you can.

Here is the link to the Aviation Magneto Article I found interesting:

http://blog.aopa.org/opinionleaders/2015/03/19/champion-from-denial-to-acceptance/

On the 48A, s/n 48A1-48A2772 uses a 8F5899 Cat # which is a Champion UJ-12 plug.
The 48A2773-up uses a Cat #9M4141 which is a Champion UJ-18YC plug.
UJ-12 equals a Champion J11C, NGK B2, or Autolite 258, 308 or 316.

The U means "auxiliary gap" also referred to as "booster gap" plugs
The J means 14mm - 3/8" reach -13/16" hex size
The Y means standard projected core nose
The C means copper plus design

I'm not sure that replacements have the "auxiliary gap" also known as "booster gap" plugs.

Thank You O.M.

I called Cat early today and they ordered the earlier spark plugs for me. I will call them in the morning and see if they have the later model plugs. I need the part # (9M4141 spark plugs). The service book calls for a plug gap of .030. The old Cat manuals are a pleasure to read, very clear photos, drafted on photo type paper, very clear instructions etc. I need to find a good quality orginal parts book for this D7E 48A.

I have to say that buying Caterpillar parts is a very pleasant experience compared to buying Komatsu OEM parts. Cat parts are available and arrive quickly! Also it seems at half the price or less than Komatsu. The plugs are only $2 dollars. I have yet to have Caterpillar charge me any freight charges or restocking fees. If you want a painful experience in life try to locate and buy Komatsu OEM parts in the USA for a Newer or Older Komatsu machine.