82' GS300L lacking power.
 

Hey, I am new here! I recently got a 1982 GS300L running but it lacks serious power. I can't seem to get above about 25mph in any gear. Tomorrow I plan to check valve lash as it was sitting for a long time and I am unsure of how the bike was kept. Plugs are fine as well. I have yet to pull the carbs back off and double-check for cleanliness however I did have them redone by a local Suzuki shop. Do you guys have any other ideas of what could create this issue?