Removal of 2 chambers
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I believe it's just another YEIS developed for the later models.
I don't see how it could possibly restrict the bike and the WR200 engines ran them and they are competition bikes, so definitely not a restriction
@Calum Also some of the 80's IT's had two bottles and there were no restrictions on these bikes. I dont think that the second one will make a noticeable difference tho.
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@valtteri Within a band of 2000 RPM centered around their resonant RPM they serve to absorb and give back pressure. When the intake port or reed valve closes there is a pressure created by the sudden stopping of the fuel/air flow from the carb. Some of that pressure enters the boost bottle and then exits back in perfect harmony with the intake opening at the YEIS systems resonant RPM. At all other RPM it does so with less force the farther away the RPM is from the systems resonance.
The YEIS is one of the ideal mechanisms that permit improvements of performance and fuel economy in the low and medium speed, part throttle operation of the two-stroke engine."
Pressure variation in the intake tract is more at low RPM than it is at high RPM, therefore the effect of the YEIS is much less at high RPM. Also it has more effect at partial throttle than at full throttle because the pressure variations in the intake manifold are more at partial throttle.So running both bottles actualy gain in Hp at the bottom end, on race Tzrs etc they are blocked off as do nothing for top end power but disrupt the fuel flow through the inlet tract. You can actualy gain about 1hp drilling the hole larger on the bottle on top of the inlet manifold, drill the hole in the bottle 2mm larger than the diameter of the hole then swill out the bottle with petrol.
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Honestly it's total codswallop that they are restrictions. They're supposed to add power. To be honest you won't notice any difference removing them. I've tried it it plenty of times. Both my DTS are 200cc now.
I know It feels Like a quick easy "tune" to make you feel like you've added power.
But invest in porting, bigger carb, better exhaust. Even cut the lid off your airbox and jet accordingly helps, and adds a nice noise
Fit the 3MB head if you haven't already. Still didn't make much difference when I had a 125r engine.
Take it even further and get a zeeltronic CDI
Don't forget the Reedswitch!
You might be lucky and have the CDI without the low rev limiter like i did, I think its a 3rm-20
Which is plug in and play on late dt125r
