• Husqvarna Motorcycles Made In Sweden - About 1988 and older

  • Hi everyone,

    As you all know, Coffee (Dean) passed away a couple of years ago. I am Dean's ex-wife's husband and happen to have spent my career in tech. Over the years, I occasionally helped Dean with various tech issues.

    When he passed, I worked with his kids to gather the necessary credentials to keep this site running. Since then (and for however long they worked with Coffee), Woodschick and Dirtdame have been maintaining the site and covering the costs. Without their hard work and financial support, CafeHusky would have been lost.

    Over the past couple of weeks, I’ve been working to migrate the site to a free cloud compute instance so that Woodschick and Dirtdame no longer have to fund it. At the same time, I’ve updated the site to a current version of XenForo (the discussion software it runs on). The previous version was outdated and no longer supported.

    Unfortunately, the new software version doesn’t support importing the old site’s styles, so for now, you’ll see the XenForo default style. This may change over time.

    Coffee didn’t document the work he did on the site, so I’ve been digging through the old setup to understand how everything was running. There may still be things I’ve missed. One known issue is that email functionality is not yet working on the new site, but I hope to resolve this over time.

    Thanks for your patience and support!

No reed valves on a 73 250CR??

spaceace182

spaceace182

Husqvarna
A Class
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?
 
Can someone explain to me how this is possible?

How does a 2 stroke chainsaw engine work? they don't have reeds! and you don't have to have them, but they sure help preformance
 
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.
 
You must log in or register to reply here.
Back
Top