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Ist reed valve on RM250

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well, I hope they all do - hard to make a 2stroke run without either reeds or a rotary valve to stop backflow of the air charge

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There were plenty of 2 strokes without reed valves (or rotary valves). I'm pretty sure that the RM models have used reeds from the first model in 75 (125) or 76 (250 and 370) though. Initially they had case induction that used a reed valve I think. I know my '77 RM 370 had reeds for the case induction. So I'm sure the 250 had them as well.

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The 1981 RM250 was the first year for the "traditional" full reed motor, before that they were a case reed / piston port setup. Is that what you were looking for?

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I'm not really familiar with a case reed. Rotary valves yes but case reeds no. My 78 Maico had no reeds or other such valves.

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This is an advertisement for a '77 Suzuki PE. Look really close at the image in the lower left, the little pink thing represents the reed valve however there's nothing between the carb and a straight shot into the cylinder. This is a "case reed" setup. If there was no reed at all it would be a "piston port" design. A "full reed" design would look like something that would belong in a '01 to '08 RM250.

77SuzukiPE.jpg

One thing that "could" be confusing is that the '89 to '95 RM250 had the intake routed directly into the cases, you could even pull the cylinder off without touching the carb or the reeds. In later years that was also termed a "case reed" set up. However, because it used a full reed block just in front of the carb, it still qualifies as a full reed setup.

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so what changes have they made since they went to cylinder reed induction in 95?

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so what changes have they made since they went to cylinder reed induction in 95?

None, they just messed with how close it was to the carb and the overall size. So really since '95 it's been a "traditional full reed" design, the size and placement has changed but the actual design has not changed.

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