Finnrpm
ArboristSite Operative
One way to check for cp vs. op on the 55 is to pull the top cover and look at the flywheel side rear (intake side) cylinder bolt access hole through the cylinder fins. The hole you'd stick your allen wrench down through to get to that cylinder bolt. On an open port saw that hole goes through 3 fins. On a closed port saw that hole goes through 6 fins. Hope this makes sense.
You mean these?
RV