I've posted this in the meteor threads but I wonder if any of the galaxy brains over here can chime in.
So I have this problem of the engine not instantly going into overrun/engine braking when riding in a "spirited" manner. The engine goes to idle instead of full overrun for periods between 3 and 20 (twenty!) seconds. The idle can be interrupted by pulling the clutch (without changing gears) or rear braking. It isn't predictable and is a dangerous design fault.
So all of you engineers and mechanics out there here's a possible explanation from a mechanical engineer who completed their masters on air cooled engines.
"The issue occurs after periods of high engine load suggesting that the engine temperature is higher than optimal. Air cooled engines only have one feedback mechanism which can control temperature and that’s to trim the fuel mixture rich. In a situation where the engine is above ideal temperature and suddenly has no load/closed throttle, it’s reasonable to expect that the ecu will take advantage of this to cool the engine as much as possible. The ecu is likely adjusting the idle speed to maximum and adding as much fuel as possible to achieve the maximum cooling effect in the minimum amount of time, therefore meaning the thermal headroom of the engine is raised again and engine wear is minimised. Liquid cooled engines, on the other hand, also have this mechanism however it's very rare that it would actually trigger. The oil/crank case temp of an air cooled engine will vary from like 80-140, but a liquid cooled one will be like 90-110, so you'd have to be absolutely slamming a liquid cooled engine to get it to do that."
Feedback wanted lads and ladies. What say you? If this is just a part of the normal operating system of the meteor then its going to get cleaned up and traded in pronto.