Dumb question.

In 82/83 was there ever a 400cc air cooled? If not than a big bore bottom end of these years has to be a 430 or 500cc? Again air cooled.

Perhaps it is a dumb question since it is easy to look at the parts sheets and see what models are on those years. As far as I know any air cooled 400 bikes were a number of years prior to 82-83 and had different cases. The 400 of somewhere around 84-85 that was in the water cooled dual shock and then the water cooled mono shock for a few years was essentially a de bored 430.

The crank for the big bore you speak of varies with displacement. Later there were different balance factors for the 500 crank, perhaps to better fit with the mono shock frame.

I checked the list of years to engine size but sometimes the list can be wrong or mixed up. Like the military 250 auto uses the same 430wr serial number. I look to you guys too just to be sure. I seen a twin shocker 400 but wasn't sure if there was a ac one. Thanks.

frans talking about husqvarna parts and model sheets.
no ac primary-kick 400, just 430 and 500.

The only way I know how to get an aircooled late twin shock is to sleeve down a 430 with the 400L/C sleeve. You have to build it, not just buy one

very true...and probably pointless as the 430 is very similar to the 400..not even sure what you are saying would work as the lc 400/430 have a much different intake than the ac 430...same port windows?

Are not the LC Cylinders center Exhaust port and AC side Exhaust port like the 250's.? None the less it would be easy to have a sleeve made, and use the 400 Piston. Assuming the windows in the piston are the same to match up to there ports.

You could likely mate a 1980 390 cylinder onto a 430 bottom end. The stroke will give the 390 cylinder the extra 10cc to make 400cc. If I had a 1980 390 cylinder I would have tried it myself.

As far as why Husqvarna never did it, I would say why bother. A mere 10cc increase would not have been worth the effort and the 430 was the logical progression.