Guys, I need some help.
The problem is my GP Stearman climbs under power. I flew this airplane 2 years ago without any problems. It sat last year without a flight on it.
Then this year I flew it and it just "skies" under full throttle. I hadn't changed anything since I last flew this in 2006.

I thought it may need down thrust so I added 1/4 inch (measures at the end of the prop shaft) downthrust. didn't help

I checked incidence: stab=0, lower wing = 0, upper wing = -.5 degrees. That seemed about right for a biplane, at least I think so.

I tried mixing in down elevator with throttle and that sorta worked. If I lower the throttle slowly (with the mix on)) it flys fine. But when I chop power suddenly, it zooms skyward.
(Yeah, I know-don't chop power suddenly)
will check the balance, but out at the field we lifted it on the marks and it seemed fine, level.

need your ideas, please

I have heard something about the interplane struts, if you reverse them (up side down) then happens just what you have described. Take a look at the Bipe thread I think it is there.

I checked out the N struts. They are installed correctly.
More ideas please....