Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

You need to remove the steam  chest cover and check the  valve is moving equally .
Your timing can not be too bad as it runs
Is the surface between valve and ports smooth?
I would try holding the engine on it side (steam chest up ) to see what happens .
Is there any oil in there .
Does adding oil help ?if it does then I would be looking very closely at the surfaces .
 Another thought is air getting past the piston ?

Piston 'looks' ok

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No piston packing
Try some graphite string around one or two grooves

Dennis, I just rang MSM and double checked with the owner John and he stated that they don't use any packing on the pistons on the Pevensey or Echuca type models.
Still mucking around with it now, I think I got the position right for TDC and BDC with it just cracking at each end. Still mucking around with the ecentric timing which I have to say is a bit of a PITA.

I have some meters of it from the Demon from years ago. How do you use it?

I actually had the same issue (along with a few others) with my Pevensey as whilst it ran ok, as soon as i hooked up something to the pulley i quickly found it couldn't pull the skin off a rice pudding!

After a lot of mucking around trying to troubleshoot the issue, i found that the slide valve was put in the wrong way!

So if anyone else has a Pevensey/Echuca with the same problem, your valve should be like this on the port face:

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One you have that set you need to make sure both port openings are equally spaced by using the nut to adjust the valve travel. If you have a reversing engine like mine, you may find you have to file some material out of the anchor quadrant if it won't run in both directions after altering the eccentric timing.

Hope this helps.