• 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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Husqvarna 250 mag engine??

Bigbill

Bigbill

Husqvarna
Pro Class
What years was the 250 mag engine offered? Did the 250 mag motor take the larger ignition flywheel similar to the 360/390 flywheel?

I see stuff listed for sale that don't match the year. Like a 82/83 250 cylinder that has a '80 reed box. It's the wrong year.
 
Is the mag engine a 250cc with a shorter connecting rod, but the same stroke to make it a 250cc? The cylinder looks similar to a 125/175 on the outside?

I assume the 360 & 390 use the same crankshaft with the larger tapered shaft on the ignition side.
 
The "Mag" is the same 250 engine, basically, from '74-'81. There are differences, the '74 was a 5 speed, and there are other updates and changes over the years, but in general sense '74-'81 250s are all the same. The only reason the "Mag" is called a Mag is because there were two (actually 3) 250 engines in '74, the older aluminum case engine (early 74 CR and WR) and the new magnesium case (late 74). And no, the rod was not shorter on the Mag.
 
Didn't the mag rod measure 35mm while the later 250 rod measured 40mm? This was why the mag cylinder was shorter. If I'm right the shorter stroke must have flown speed wise.
 
The Mag does not have a shorter rod, nor does it have a shorter cylinder, I dont know where you got that idea from. There is a different rod for the non primary kick engines (250/360/390/420) and the primary kick (250/400/430) but they are all 135mm center to center.
 
I must be wrong. I built a mag engine using a Yamaha rod. We ground the lower end so it fit the husky crank. The upper end was ok. It's written up in Craig's husky news letter in my name I wrote the article. The rod was a tad short but when there was nothing else available it worked. It needed a new husky lower crank bearing. I used a Yamaha crank pin I turned the length to the husky width.
 
The rod for the #2033 74 250 Mag motor are 125mm centres and was for that year only :) . Same stroke as later engines, am building a mag motor with a later 135mm rod at the moment with a spacer under the cylinder, as the longer rod has more leverage.

IMG_1192_zpslzyp428t.jpg


 
Well, there you go. This is the first I have heard of the shorter rod in the 74 250. I will have to look at my 74 Mag and 76 250WR engines when I get home, I don't remember them looking different on the outside or the Mag having a shorter cylinder.
 
mag is shorter and the non primary to primary are same center to center (135) but non primary bottm end is narrower than the primary. When they did not have you coud use a AC KX 250 rod and thin the bottmom by like 12.5 mm
 
I knew I had a shorter rod in a mag motor. This was 20/25 years ago. We learn from each other thanks guys. Yup the std rod is 135mm but the mag rod was 125mm. The 250 piston goes deeper towards the crank. The cylinder is lower. They lowered the height of the head and stroke but still it's a 250.

Sorry brain fade and old age is setting in.


Longer rod more torque but it won't rev up as quick. The 250 mag motor is a screamer?
 
Joe Chod said:
mag is shorter and the non primary to primary are same center to center (135) but non primary bottm end is narrower than the primary. When they did not have you coud use a AC KX 250 rod and thin the bottmom by like 12.5 mm
Click to expand...

Right I used a Kawie 250 rod, a Yamaha crankpin, a husky lower rod bearing. We ground the width of the lower rod and turned the length of the crankpin to match the husky crank width.
 
Exactly that lowers the deck height on the cylinder. Now I would port it, polish the inside of the crankcase and add the internal rotor on the ignition. The short rod I'd say hang on. It would hit really good.
 
Bigbill said:
Exactly that lowers the deck height on the cylinder. Now I would port it, polish the inside of the crankcase and add the internal rotor on the ignition. The short rod I'd say hang on. It would hit really good.
Click to expand...
you know rod length has no effect on stroke right? stroke is determined by crank throw..
 
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