• 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.

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Will a Later Reed Valve top end fit on my 1972 250

chamber66

chamber66

Husqvarna
B Class
As in the title. But also why are reed valves considered better? Maicos didn't use reeds til much latr and are highly regarded.
just asking :confused:
 
piston ports have a habit of "loading up" if the throttle is opened too wide at too low a rev range..the fuel in the fuel air mix effectively drops out at the low speed in the engine and acts like the choke is on and bogs the engine down like its flooded....when this happens, you need to flick the fuel off, keep the throttle pegged in neutral and hopefully the lack of fuel will eventually clean the motor out before the plug poohs itself.... a reed valve prevents this happening pretty much...

ive seen plenty of older maicos sitting on the side of the track blub blub blubbing away with the throttle wide open and the rider praying it will clear out rather than a plug change...
 
The 74 250CR has the mag engine, i.e. the next generation engine, making the reed assembly incompatible with the 72 250WR or any other pre-75 Husky engine. There was an aftermarket reed unit for the 72 but my understanding is that it didn't work as good as the later factory setups. The intake on the 72 is far smaller than the 74cr, maybe that has something to do with it being ineffective.
 
surprize, no worries.......I don't know much about the 80's stuff myself other than they're awesome to ride.
 
You may want to consider your riding preference before changing to a 74 reed cylinder. If your an MX track guy who's used to riding high rpm machines then this may be something to entertain but if you're a woods/desert rider then it may not be a good idea due to the loss of torque over your 72wr.

Heres a couple interesting bits of info from a 1974 Cycle World road test of the 74 250cr. The hp/torque graph clearly shows that this application needs to be ridden at 5500 to 7500 rpm, IMO that's not optimal for a 250 in a woods or desert terrain. However on a closed track it would work, Mr. Mikkola proved that.

The article below states that the 74 250cr piston rides on top of the same rod as previous yrs. Knowing HVA this isn't surprising back in those days. So the only thing would be, as jimspac stated, is that the stud pattern and the center case sleeve opening are the same size. Maybe a 250 aficionado on this site that has some parts from both eras could measure them and let us know.

One other thing that comes to mind is the difference in gear ratios between the 74cr and 72wr. My info shows that they're quite different.

DSCN2493 B.JPG


DSCN2494 B.JPG
 
Since you are showing ownership of a 72 250WR, I am suggesting that you look for a 75 or 76 250WR top end. Those bikes did very well here in New England enduros so they did not give up significant low end
 
It is a wr, as I gave up trying to find a CR :(. It's going to be used for MX, so I want to make it as good as I can for that discipline within a reasonable budget. Our tracks over here are quite tight, without too many long straights. So i'm hoping the WR will work well, if not I will come back to the ratios at a later date.
Quite confused now as to whether to go with reeds or not LOL
. The other thing to consider is the class it will be in is pre74, so don't want to come to far from the original bike. Would you by any chance have to graph for a non reed 250?
John
 
I do not as I never had a large case model. I was going to buy a 73 250CR in 1974 from a friend of my father but could not swing the price. I ended up buying a 1969 Husqvarna 250 round case and found out it was a 360 Sportsman when I went to our local dealer to get a replacement 2nd gear,

As far as adding a reed to your cylinder, you still would either find a reed cage or have one made, The accessory reed cage as mentioned previously was said to be insufficient so you would also need someone with engineering ability and fabricating ability to create a bolt on or weld on cage that would accept a Boyesen or V Force reed assembly.

Period correct for the 1974 class would be bolt on
 
With piston ported engines with no reeds you can change the port timing. We cut 1/8" off the bottom of the piston. Raise the exhaust port and polish it. Then lower the intake port.. the carburetor is 34 or 36mm? I'd go one size larger. Probably a 38mm.
 
Info on Huskys and Reeds that might be of interest. (Part 2)

Boyesen Prototype Reed on Oval Case:

5 Boyesen Oval Case.jpg

Two popular (back in the day) Reed Conversions. There were others, though not as common.

DH Enterprises:

DH Enterprises - Copy.jpg

GEM:

GEM - Copy.jpg


Also, Husky Newsletter #23 has an extensive article on installation with diagrams for porting and piston mods.
 
That's 30hp @ 11,000 rpm that's not to shabby for an old bike with a few upgrades. If you do the porting she really lights up. That's with no thunder products UFO too.

When building a dirtbike, motorcycle or race car every change of improvement is like adding a tooth on a gear. Little suttle changes matter too. You can putt, crawl, or light it up.
 
suprize said:
piston ports have a habit of "loading up" if the throttle is opened too wide at too low a rev range..the fuel in the fuel air mix effectively drops out at the low speed in the engine and acts like the choke is on and bogs the engine down like its flooded....when this happens, you need to flick the fuel off, keep the throttle pegged in neutral and hopefully the lack of fuel will eventually clean the motor out before the plug poohs itself.... a reed valve prevents this happening pretty much...

ive seen plenty of older maicos sitting on the side of the track blub blub blubbing away with the throttle wide open and the rider praying it will clear out rather than a plug change...
Click to expand...


She's loading up cause the needle jet is too rich. I experienced that when I put the 40mm carb on the 390cr. I talked with a bike builder in CA who races a T500 Suzuki with twin 40's. I ordered leaner needle jets. He knew what I was doing. He thought he was the only one in the country going to bigger carbs. I put the needle clip in the middle position, went. Leaner on the needle jet then played with the main jet. Trust me the 390 came on like gangbusters, it wasn't a ride for the faint hearted.
 
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