• 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 The previous version was outdated and no longer supported.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!

390 or 420 top end. How to tell?

pn27416

Husqvarna
AA Class
Guys,
A couple weeks ago you helped me buy a 1980 390 with a 420 top end. I,m happy to say I now own it. Comparing it to a 390 motor I had already, I see no difference. Is there a way to spot the difference from the outside without pulling the head?
Pete
 
I was just comparing 420 to 430 last week. The 430 casting seems to be the same as the 420 but shortened on top. I couldn't figure out about the bottom one of the 420 ones was shortened and the other maybe was maybe wasn't. The cylinder heads don't interchange 420 430. I have two 420 top ends loose and one on the bike, two have the spark plug pointing straight up and the other one is angled. One has a small hole to make starting easier going from inside the exhaust part of the head to a hole above the exhaust port opening.

Does the 390 have a divided exhaust port like the 360? If not it kind of seems not a great idea the 420 bore/stroke ratio as about as oversquare as any model they ever made isn't it? The 420/430 piston must not be in balance for the crank weights of a 390.

The 420 would have an 86 mm bore I think I could make a small wood stick that size and figure a way to see if that was in fact your bore diameter working through the exhaust port. I think 9 fins for the ones I am typing about.
 
I think the 390 is a divided exhaust port. I,ll look for sure later today. Both cylinders do have 9 fins and the heads look the same. Pipe looks to be untouched stock. Someone here mentioned was it modified to fit the 420.
 
George at Uptite told me the 1980 390 was the only cylinder that has enough cylinder wall thickness to accept the 420 piston.
He also said the stud spacing is wider in the 1980 390, as Husky was getting ready for the new cases and cylinder for the 420 in 1981.
My 79 390 has a single exhaust port (not bridged) and the studs measure 2.75" front to back and 3" across. Difficult to measure with the cylinder on the bike though.
Ron
 
I think the 390 is a divided exhaust port. I,ll look for sure later today. Both cylinders do have 9 fins and the heads look the same. Pipe looks to be untouched stock. Someone here mentioned was it modified to fit the 420.

PN see post #2 here highlighted at bottom of page scroll thru PDF until you find the right section... will detail the pipe modifcation...in detail.

http://www.cafehusky.com/threads/vintage-husqvarna-service-bulletins.1312/#post-24612

Hope this helps...

T
 
Thanks T I'll give a look and Ron I'll see what I can.
Oh and heres a pic.
 

Attachments

  • IMG_0579.JPG
    IMG_0579.JPG
    178.9 KB · Views: 25
Back
Top