MTH j class 611 model 1105 binding issue

Additional photo

So to clarify, it’s just the piston and rod that are stuck in the smoke unit bore? ….can you rotate the flywheel by hand now and verify the rest of the driveline is ok? ……if it’s just the smoke piston stuck, more than likely some old smoke fluid has turned to varnish and has gummed up the works. Most of the time the jam is minor, and a little twisting and pulling gets the piston moving again. Best to remove the piston from the bore, clean all the parts and re-assemble. If there’s an O ring on the piston, remove it and discard it, ….leave it off, it’s not necessary. …..I can’t remember if MTH used an O ring on the piston or not.

Pat

I’ve repaired a few of these when I worked at MTH in service.  The piston swells causing it to bind in the bore.  Remove the piston, clean the bore and lightly sand the piston so it has more clearance.

Yes the flywheel spins freely,removing the screw from the arm was my first move.now to get the piston out w/o strong arming it.maybe a little light oil to help break it loose? Excellent replies to my questions guys.

@Ironman56 posted:

Yes the flywheel spins freely,removing the screw from the arm was my first move.now to get the piston out w/o strong arming it.maybe a little light oil to help break it loose? Excellent replies to my questions guys.

To avoid any unnecessary damage to the rest of the frame, disconnect the wiring from the smoke unit, and remove the smoke unit to work it on a bench.

Pat

You should have just added this to your old post so folks with same engine binding problem would know the issue.  Use a break free type solvent and work the piston out.  You can use fine grit sand paper or steel wool to clean bore and piston as mentioned.  Test fit and sand again as necessary.  I think there may be a seal on the piston but don't remember for sure.  G

Well, I have the J running smoothly again.After applying a small amount of loosening compound,I let it sit for a bit.It came out without much of a fight.Honing the piston and the bore with a fine grit sandpaper did the trick,it did indeed take two sanding sessions to get it to plunge smoothly.And there wasn't a seal on the piston.

@GGG posted:

You should have just added this to your old post so folks with same engine binding problem would know the issue.  Use a break free type solvent and work the piston out.  You can use fine grit sand paper or steel wool to clean bore and piston as mentioned.  Test fit and sand again as necessary.  I think there may be a seal on the piston but don't remember for sure.  G

FWIW, this looks just like the K-Line smoke unit, and it had a O-ring on the piston to seal it.

I don't own one of these.  But I'm wondering about the possibility of a radical smoke-ectomy.  For the record, is it possible to remove the upper worm wheel entirely?  (the one that drives the smoke piston)  If it is possible to remove it, would doing so adversely affect the gear mesh with the lower worm wheel that drives the train?

Any type of mechanical smoke is going to adversely affect slow-speed operation.

@Ted S posted:

I don't own one of these.  But I'm wondering about the possibility of a radical smoke-ectomy.  For the record, is it possible to remove the upper worm wheel entirely?  (the one that drives the smoke piston)  If it is possible to remove it, would doing so adversely affect the gear mesh with the lower worm wheel that drives the train?

Any type of mechanical smoke is going to adversely affect slow-speed operation.

I’ve converted quite a few of these to PS1 smoke units, …..you can ditch the entire smoke unit and the upper gear. Does not affect anything, in fact, it runs smoother.

Pat

I enjoy the smoke feature,so as long as this one works i'll continue as is.If not it is good to know its a simple fix to replace or disconnect and operate without.