I am planning a trip on my Goldwing F6B. 10 days in August. from Khonkaen to Northern Thailand
I am not sure of how much of Northern Thailand you have visited but there are many roads as good as or better than the MHS loop..............and stunning scenery..........10 x days so you have a fair bit of time, if it was me I would make your way to Loei 1st night and then across to Nan for the 2nd night, leave Nan on the 1091 or 1148 and head to Chiang Kham and then follow the Laos border up past Phu Chi Fah and Doi Pa Tang onto Chiang Khong or Chiang Saen for the 3rd night, lots of mountains and great views, except if the rain comes
From here go through the Golden Triangle to Mai Sai and then follow the Myanmar border down to Chiang Rai for your next night, that would be 4 x nights gone, alot depends if you are sight seeing or just riding, are you with your missus or are you looking for entertainment ?
Leave Chiang Rai and head upto Doi Mae Salong and then follow the Myanmar Border again down to Fang for your 5th night, if time permits go up to Doi Ang Khang, one of the steepest roads in Northern Thailand.......................from Fang you can easily ride to Pai for the night, and then you are on the MHS loop, this would be the 6th night and you would of seen alot of Northern Thailand, all these roads good, no issue on the Goldwing IMO
This would then let you wander down to Mae Hongson for a night, or Mae Sariang...................leaving you 2 x nights to get back to Khon Kaen..........................things could change if you get a very wet day, rarely rains all day Imo....................do you intend to do alot of sight seeing ?...............................if you havent been to Northern Thailand I would forfeit the MHS section and spend more time exploring, Nan district has many amazing day trips, same as Chiang Rai, there are so many good roads around.
All these photos below were taken in August 2019
Nan district.........
This pic overlooking Myanmar up in Mae Sai district.....................
Plenty of temples to see in Chiang Rai............................