MTH Ho K4 Flywheel/Drive connection Problems

Hi there, I just recently got a first run MTH Ho K4. All was going well till today when pulling a train it just stopped randomly. The smoke unit was still going and everything else sound lights etc. were still going as if it were moving. I took a look inside and noticed that the flywheel when spun wasn’t spinning the actual drive connection to the wheels. I noticed a set screw and tried tightening it but it was already tighten. I was able to get it running then it stopped again from the same issue, while pulling nothing. I am not new to MTH as I have 2 Berkshires that have been ran for a couple years. I am not to sure how to resolve this issue, I think I could but MTH never released any exploded diagrams of their ho models, so this makes me stuck. If you could give me any advice on how to fix this I would greatly appreciate it!

I have not worked with MTH locos before, HO or otherwise (I do have an O scale snowblower). Well, according to their website the diagrams are “coming soon”.

Maybe wait?

I would wait but it will stay like that, they have no plans to release them after Mike retired. It has been 4 years about give or take, and the designs are not the same so it would be really hard to make all of them.

Here’s a thread from another forum with pictures of the drive involved:

https://www.modeltrainforum.com/threads/mth-k4-universal-joint-problem.193635/

See if this resembles what you have. Note what they say about a screw under the tach strip.

Might be similar I will try moving the joints up to the flywheel more, if it is possible.