I would not take the big bike on any of the passes around Telluride, if by those passes you are including Imogene and Black Bear. Those passes are pretty technical and VERY steep in places. But, I watched a guy come down Black Bear on an old KTM 950 like it was nothing... I
might do Ophir on a big bike depending on reports near the time was going to be doing it. Bolam pass (South of Ophir) was fairly easy when I rode it back in 2010. This last time in 2018, it was considerably rougher and more challenging, and I was on my KTM 530 instead of a KLR 650 like the first time.
I've done the main section of Engineer from Lake City heading West on an 1150 GS, and could probably do it on a 1200 GS. The West side is the steeper and more technical side. When you reach the turn off to go to Animas Forks/Silverton on the West side of Engineer, take that fork! IF you go North and continue on Engineer to where it drops out on US 550 just South of Ouray, that section is extremely rough! Most jeep rental agencies now require you to sign a promise NOT to take their jeeps on that section because so many of them were getting torn up trying to go through there.
Cinammon Pass between Animas Forks and Lake City would not be bad on a big bike. I don't recall any sections that were particularly challenging.
Corkscrew is steep, but not especially rough. There was one short skree section heading up toward Hurrican Pass and Lake Como that was pretty rough, but if you were careful you could probably get through it without too much trouble.
Road conditions change constantly out there. If they have been getting much rain the roads can get VERY rough and loose.
The only good thing about most of those passes, and bad depending on your perspective, is that they are well traveled during the summer months. So even of you are technically riding alone, there are usually other people around. Whether or not they will be willing to help you...
If you have a particular date in mind, I would just post up here. That is a popular riding area and there are always folks here that head out there every year. I bet you could find a few folks willing to head out there and at least ride part of the time with you.