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Not a Rotax expert but for engines in general, no. Cold engine, high oil pressure at idle, falling to at least minimum pressure when normal operating temp is reached. Then pressure rises and falls with engine rpm. Is the engine at normal operating temp when you see this? How was it behaving prior to you noticing? If the Rotax has a port you can access with a wet line gage you can confirm proper operation of the pump then you can focus on the indicating system.
High pressure on start with oil temps cold. Oil pressure will drop slightly at normal temperature and operating rpm.
At idle, with oil at normal temps pressure should be above 40 psi.
what Bob Mcdonald said. Mine at times does similar.
Does it have a genuine Rotax oil filter on it? "they" say other brands may have the bypass valve set for incorrect pressure...that could affect it. And is the OP gage electric? in my experience electrics aren't as reliable as direct.
But if it's in limits it doesn't sound like a problem. Mine will go down in cruise to lower limit at times. Never have figured that out. It always comes back up after a while. dunno...
I'm pretty sure my engine does that sometimes too, I wouldn't worry as long the pressure stays within limits.
A great place for info. is the forum on www.rotax-owner.com.
I think I pay $25.00 a year for full access to the site, it's well worth it if you have a rotax engine.