• 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.

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What the difference between 360 & 390?

ruwfo

ruwfo

Administrator
Staff member
What the difference between the 360 & 390?

Ok, I know that a 2nd over (82.42) 360 is also a 390 std bore, but if you bore the 360 cylinder
to a 2nd or 3rd over, do you now have a 390 not a 360? I guess you do right?

The cylinder grew in height in 1977 when the 360 went to a 390 & gain an extra fin (8 vs 9),
so I'm guess Husky lengthen the rod too? and that the piston wrist pin stayed in the same location
as on the 360.

I ask because, I'm getting ready to have my 360 cylinder bored, it's at STD bore now &
I'd like to know my piston size options. I see Husqvarna-parts has 1st-3rd over , but I won
a Wiseco piston on Ebay, which is a slightly smaller size then 3rd over (sort of a 2.5 over) &
until I get it was wondering will that work too.

Husky John
 
A 360 is basically big bore 250,a 390 is a bored and stroked 360,64.5 stroke for 250/360,71mm for the 390,all 3 use a 135mm center to center connecting rod,the 360/390 both have 37mm compression height pistons{centerline of pin bore to top crown}The 390/420 conversion{actually 412cc} is an 86mm bore for a 390,The 430 is a bored and stroked 390,74mmX86mm,same 37mm comp. height and 135mm rod,the 500 is a bored and stroked 430,88mmX88mm,with 145mm con rod.Kinda like the small block/big block chevy or Ford FE series of the dirt bike world.
 
Post 2 pretty much cleared up the origional question but gets off track about the 500 it is 84mm stroke 86mm bore on a signigfincantly more massive piston but still same bore as 420. 420 piston is the same as 430 air cooled.
 
Thanks Dave, that's answer the question , & also explains the 390 motor I got with a broken piston skirt, that I sold to Jim.

He said it looked like the piston had actually hit the crank & broke the skirt & then the cases. Well that now makes sense, some
knuckle head must have used a 360 piston in a 390.
 
Actually I seem to recall the 360 has a 67mm stroke as I had noticed a 4mm change from 360 to 390 and 390 to 430.

If you found a 390 crank, that may fit in the 360 cases but also remember that Husqvarna went from single point mounting on the front of the 360 to dual point on the 390. And as you reminded me that Husqvarna does everything for a good reason.....
 
so stupid question as I am not well versed in this generation Husky
typically when an engine is stroked as in a different stroke length, it also changes the piston height profile to compensate for the differ port timing from stroke
later the 430 500 shared a bore size, but nothing else
 
2premo said:
so stupid question as I am not well versed in this generation Husky
typically when an engine is stroked as in a different stroke length, it also changes the piston height profile to compensate for the differ port timing from stroke
later the 430 500 shared a bore size, but nothing else
Click to expand...


When Husky went from a 360 to 390 they changed the stroke and the cylinder length and port timing. Used the same piston and rod.

Marty
 
motomwo said:
When Husky went from a 360 to 390 they changed the stroke and the cylinder length and port timing. Used the same piston and rod.

Marty
Click to expand...


that's a clever trick, but other makers just started over on stroke changes, so did Husky later, but still a cool trick
 
2premo said:
that's a clever trick, but other makers just started over on stroke changes, so did Husky later, but still a cool trick
Click to expand...

The 82-84 500 motor required a new rod, crank, piston, cylinder and head. 500's use the same cases as the 430. The 390 can also use the 430 pistons. The 1980 390's and 420 auto can go all the way up to 87.00mm bore!

Marty
 
motomwo said:
The 82-84 500 motor required a new rod, crank, piston, cylinder and head. 500's use the same cases as the 430. The 390 can also use the 430 pistons. The 1980 390's and 420 auto can go all the way up to 87.00mm bore!

Marty
Click to expand...

Yes, i made my 80 390 into a 420
 
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