From my understanding of how the decompressor mechanism works it should be fully "closed" when the bike is not running and the decompressor rod will slightly press on the exhaust valve before the cam lobe does to let off excess compression as the motor starts, then centrifugal force from the running motor holds the decompressor "open".
The problem may be that the spring has lost some tension or is not strong enough and on certain shutdowns the part of the mechanism that keeps the valve open rests on the valve bucket on shutdown preventing the decompressor mechanism from fully closing/resetting.
My thought is that switching to a slightly stiffer spring or adding an additional turn to the existing spring may help the issue because the mechanism may now fully close on a shutdown before the motor fully stops spinning which in theory should prevent the issue. I checked the parts list for a 2020 sefr and mechanism looks to be the same p/n as the older models. I do believe the intake cam timing has been changed on the newer models possibly to try and help with the issue?
The only problem i can see is that if the spring tension is too strong it may cause the decompressor mechanism to stay open at idle causing excessive wear. but if it were to work every time it would save a lot of wear on the starting system.
