Kohler M18 engine question

[rtd]

I removed the spark plugs from the M18 engine. They were Champion RC12YC. When I checked the engine manual, the spec was for RV17YC. I purchased a listed equivalent and found that the projection on the RC12 is 12-13mm greater than the RV17. Not knowing much about the Magnum line of engines, I was/am confused. I thought that the longer reach plug might interfere with the piston. Since the engine did run, it didn't interfere.

Has anyone had a similar experience? I could try the RV17 plugs and see what happens, but I'd like to better understand whats going on.

Thank you

 

[MossRoad]

I'd put what the factory specs call for. Maybe someone just had the others laying around and threw them in?

 

[tomplum]

NGK TR4 is a good plug for these. You didn't say what the listed equivalent plug you bought was. I'd think it's one of those things that it would run with anything, but the tapered seat plugs VS the flat seats will make up for some of the length.

 

[Stimw]

Here is a Champion chart that explains the numbers and letters-
https://www.sparkplugs.com/Data/uploads/Charts/Champion_Numbering_System.jpg