[RATAYLOR]

Fouled a set of plugs 90 mi. out of Daytona Bike Week '88 on the '78 Shovel. Luckily, a more seasoned rider carried a spare set for his '86 Evo. Got to the local H-D shop where they suggested using H-D 5RL's('80-82 Shovels) because they were a HOT plug. The electrode extended past the end of the threads more than any plug I have ever seen before and since .(see pic) Was concerned about the valve and/or piston clearances but said not to worry. Put them in and been using them ever since. Went to the local dealer recently but have been discontinued. Strolling thru Walmart and saw some Autolites #985's(sold in packs of 2 @2.95 a pack) with same thread reach which & looked like the same extended electrode. Now, I'm assuming that the further the electrode is extended, the hotter the plug across any brand. Does anyone else have an IMO about this? Thanks, RT.

[fxdxsteve]

try here

Spark Plug Interchange Guide

[kenfuzed]

The 5RL plug was actually stock on 82-84 Shovels, but if that guy was using them on his Evo probably had issues with oil fouling so he was using the hotter plug to burn it off. There are a few plugs that are identical from different makers. Champion makes the RN13LYC and Autolite makes the 2417 which are both inexpensive.

Here's an updated cross reference of plugs:
Harley Spark Plug Cross-Reference

[CD]

Remember that for points type engines you want to use the N12YC or N13YC not the resistor type which is indictated by adding R as the first letter. Many, many, many early electronic "V-Fire" ignitions were chucked out in favor of the then much more reliable points and condensor.


Night Rider has this nice chart on their site:
Spark Plug Interchange Guide

BTW, the N12YC is the same plug my Dad used on an old small garden tractor! Sort of gives credence to the theory that an HD engine is really a tractor engine in disguise eh?