Robins EH35C

[Cartmaster]

Also, if it is the stem seals causing the problem, you will notice the smoke mainly when you slow down and then hit the gas again. When the engine is working hard, it is unlikely to smoke. On an engine that idles, smoke is seen after idling and when hitting the gas after coasting. It will be a similar case with your engine, but less pronounced as it does not idle the same way as a car. Once you have checked all other avenues and decide to change the seals, I agree that it is worth checking the guides and if suspect, change them too.

A smoking Robin engine, usually turns out to be an issue with oil passing through the PCV, but if sporadic as you say, it could well be guides and/or seals.
When it smokes is key to diagnosing this. If it just puffs after coasting, its probably seals. If under load while driving, more likely to be PCV. If your compression was low the rings would be suspect, what at 180 psi its unlikely.