DT125R ARCHIVE

The Yeis is the one on the left. As the air getting sucked into the engine passes the venturi in the carb it sucks up fuel and creates the air/petrol fuel mixture. As the piston comes passed the inlet port and blocks it some of the mixture doesnt get in and the reverberation goes back and air passes backwards over the venturi in the carb again and sucks up more fuel. this gives you a double rich mixture. The YEIS bottle stops this and allows the reverb to go up into the yeis and means there is a fresh store of atomised mixture ready and prevents this double rich condition from entering the engine.

This usually happens around 4-5k rpm just before the powerband kicks in and you get whats known as a flat spot ( it would show on a graph of the power v revs). It's said that the boost bottle should be the same internal size as the displacement of the engine. so the boost bottle of the DT should be 124cc but ive never checked tbh.

The other bottle connects onto the airbox- carb joint piece and is said to be a restriction. I've never played it with so wouldnt know myself.

i taped off my boost bottle reading all the restriction hype

didn't notice any gains though. I do find it hard to understand what it could possibly do though

I dont think anyones claiming the yeis is a restriction. I'd agree that the other is almost certainly not a restriction either. As you say its fitted to the WR200 which is a competition bike. I have one on mine. Strange that the Yz's dont have anything like that on. I cant see what its purpose is at all so if anyone finds out please post up. No one has ever seemed to notice a difference with or without it.