No reed valves on a 73 250CR??

Took the intake off of my 73 250CR and there is no red valve? So how does this engine work with no reed valves??? Looked in the parts manual and it shows no reed valve or reed block. Can someone explain to me how this is possible?

The piston skirt is the valve, reed valves didn't exist on early dirt bikes

Reed valves were introduced on Yamaha Enduro and MX models in 1972. Husqvarna first used reed valves with the MAG 250CR released in 1974.

It's a piston ported engine. The first trick we did was to cut 1/8" off the bottom of the piston skirt. This changed the port timing. We raised the exhaust port and lowered the intake port. This gave the engine a longer duration on the intake and the exhaust port opened sooner.

Just for ha's, ha's we took a '71 Suzuki TS 125 and cut the bottom of the piston 1/8". Advanced the timing a tad. I put kx80 rear shocks on it so it had some suspension. We beat kx80's in the straights. You should of heard the kids complaining, egos were hurt in this process. Just when they thought they had game a POS looking antique bike beats them. My point was to make the kx80 kids ride harder nothing is a given. You have to up your game to be a head. Again no reeds. Nothing wrong with old technology it's good for a few laughs in the high tech world.

early pp engines had a bad habit of filling up with fuel (loading up) if too much throttle given at too low rpm / high gearing. it was common to see guys on the side of the track holding the throttle wide open with the bike barely running and sounding like the choke was on. eventually it would clear (or foul the plug). the reed valve effectively prevents this occurring by shutting the fuel supply as soon as the crank pressure changes.

The intake is timed by the piston skirt, when the piston is coming down, the piston skirt closes off the intake passage between the crankcase and intake manifold. Pressure is then being created in the crankcase by the reduction in volume due to the downward travel of the piston. When the piston is low enough, the top of the piston uncovers the transfer ports and the fuel/ air is blown upward through the transfer ports into the cylinder. The piston then begins to rise. Volume increases in the crankcase due to the upward travel of the piston and a vacuum beings to develop in the crankcase. Once the piston skirt uncovers the intake port, the vacuum draws the fuel/ air mixture into the crankcase and it all starts again. The longer the piston skirt, the slower the timing and lower the rpm the engine makes power at.

This was proven at the country fairs in speed cutting with the Husqvarna saws. The 100cc saws were animals. I set the rakers for pine at .090" per tooth. I did eight cuts, bored two holes straight in, in 17.5 seconds.

Thank you all who replyed! Great explinations! I am now educateted!

edjamacated...get your spelling right