Ok, So if someone was dumb enough to have removed the plastic fitting and breather hose from the top of the crankcase, and then a few days later that same dumb person started cleaning the years of dirt and debris from the cylinder fins and various surrounding areas, only then to see the open hole that inevitably swallowed some filth……where would said filth end up? Just curious what would happen if someone was that stupid.   Let’s assume that it was a really filthy DT175B.

There is a little "chamber" that the vent opens into... ultimately gunk could get into trans.

Depending on how much debris made it into vent, I'd probably prop engine upside down over a bucket and pour copious amounts of diesel fuel into trans drain plug and let drain out of vent hole.

Thanks Mark. I swabbed down inside the vent hole with Q-tips and they bottom out in a short amount. The fuzzy tips brought up dirt for at least 6 swabs. I am going to do your suggestion for piece of mind. I’m still shaking my head…..

It's probably not that bad at all. 

Here's a link to an ebay set of cases so you can see the triangular chamber the vent fitting is in.  There's basically a narrow slot between the case halves that vents trans to chamber to fitting. 

ebay link

Light coat of oil or grease on q-tip might get most

Thanks for the link Mark. Now that I see the chamber area I think your suggestion of greased Q-tips would allow me to thoroughly clean it up. I’ll make sure I swab outward to avoid pushing anything thru the gap.

Gears are pretty tough. They'll chew up anything thats not steel that fell down there. Come out in the next oil change.

So it's not really a crank case breather as that wouldn't be very good on a 2 stroke more a transmission breather.