MTH PS2 Engine Jerking in DCS Mode

Check and see if the flywheel is loose on the motor shaft.  Also, check the tach reader spacing it should be around 1mm.

I’m not familiar with the std gauge engine. However, your issue reminds me of trouble we had and still have with our two PS2 PRR P5as.  These engines have 3 drive wheels,  but only one has a tach reader. The engines stall or jerk if the wheel with the tach reader looses traction.  Any issues with traction tires lead to this, but oftentimes it just doesn’t like a curve or section of track for no good reason. The issue usually appears at low speeds.  Unfortunately I don’t have a solution to the problem other than having perfect track.  

I glossed over the STD Gauge, that explains some things.  In the STD Gauge engine, the tach flywheel is geared from the drive and there's plenty of places for things to go wrong.  Check the linkage from the drive to the flywheel, a good chance you'll find the issue there.

@gunrunnerjohn posted:

I glossed over the STD Gauge, that explains some things.  In the STD Gauge engine, the tach flywheel is geared from the drive and there's plenty of places for things to go wrong.  Check the linkage from the drive to the flywheel, a good chance you'll find the issue there.

Yeah it’s a geared shaft that drives the tac wheel.  I’ve watched it spin an everything is smooth.  The tach reader is on a fixed bracket, non adjustable without modification, but looks ok.  I did find some info this particular engine has some known factory issues with the gearing alignment.  I’m guessing there must be some very very slight binding happening.  

Sean, now you've got me curious... How about posting a couple photos of the mechanism?  Maybe also videos of it running smoothly in conventional, and bucking under DCS.  Sorry you're having this problem, but maybe we can all learn something, or at least document the phenomenon for the next person.

@Ted S posted:

Sean, now you've got me curious... How about posting a couple photos of the mechanism?  Maybe also videos of it running smoothly in conventional, and bucking under DCS.  Sorry you're having this problem, but maybe we can all learn something, or at least document the phenomenon for the next person.

I'll get some and post them. 

@Sean's Train Depot posted:

Yeah it’s a geared shaft that drives the tac wheel.  I’ve watched it spin an everything is smooth.  The tach reader is on a fixed bracket, non adjustable without modification, but looks ok.  I did find some info this particular engine has some known factory issues with the gearing alignment.  I’m guessing there must be some very very slight binding happening.  

Smooth is one thing, is there any significant gear lash in the drive to the flywheel?