• 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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    Thanks for your patience and support!

390 to 420/430?

D

demmick

Husqvarna
A Class
hello,
another newbe question. i have a 1980 390 complete bottom end (no head or cylinder)but have access to a 1981 430 top end that to my understanding will bolt right on.
can i in some way make this work with out to much hassle? im thinking to go to 430 i would have to change the rod to a 430s to get the right stroke?
and to go 420 i would have to shave the jug or head (using the 390s crank/rod).
am i thinking right or am i out in left field someware.
thanks for any insight.
demmick...
 
The 430 air cooled cylinder shares the same stud spacing as the #2080-#2084 390,{and 1980 and 1981 250's,and some 79-80 390 automatics,all 81-82 420 automatics}Your stock rod is 135mm.Piston compression height is 37mm.Stroke on the 390 is 71mm,74mm on the 430.I don't know if the 430 heads' counterbore will fit the 2080 390's sleeve,but the 430 spark plug location will interfere with the 390 pipe.The cylinder studs are longer on the 390,spacers could be made under the cyl head nuts.The 420 auto top end will drop right on with no machine work necessary.430 STD bore piston is only 85.92mm OD to fit in 85.96 ID cylinder,will have too much clearance in a 420 auto STD cylinder {true 86mm} if you are swapping used stock parts.
 
390Dave said:
The 430 air cooled cylinder shares the same stud spacing as the #2080-#2084 390,{and 1980 and 1981 250's,and some 79-80 390 automatics,all 81-82 420 automatics}Your stock rod is 135mm.Piston compression height is 37mm.Stroke on the 390 is 71mm,74mm on the 430.I don't know if the 430 heads' counterbore will fit the 2080 390's sleeve,but the 430 spark plug location will interfere with the 390 pipe.The cylinder studs are longer on the 390,spacers could be made under the cyl head nuts.The 420 auto top end will drop right on with no machine work necessary.430 STD bore piston is only 85.92mm OD to fit in 85.96 ID cylinder,will have too much clearance in a 420 auto STD cylinder {true 86mm} if you are swapping used stock parts.
Click to expand...
 
may just drop the idea. you say the studs on the 390 are longer does that mean the 430s cylinder is shorter?
i think i was tring to do the 420 conversion using the 430 cylinder/head boaring the 430 to 86mm.
but was unsure what other issues may arise.
thanks..
 
The 430 cylinder bore is 86mm stock and that is equal to the 420 kit that was bolted on the 390 to start with. Use the 430 piston with the 430 cylinder and it should be fine
 
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