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Andy, It is difficult to get valves that don't leak a little. My preference is to use a vacuum pump and gauge to check the leak down rate to judge my valve sealing quality. I use one of the inexpensive brake bleeding pumps found at Harbor Freight. If you can pump down the pressure to 25" of Hg...

Norm, Work with the seals you currently have first provided they are not damaged. Gently blow out the soft seal from the brass housing using pressure air. Reverse it and seat it as shown in Canadianhorsepower's illustration. You did not say if your spring is holding the needle against the soft...

Norm, You have narrowed it to the needle assembly. You need to very closely inspect the needle seat and the soft seat for imperfections or damage, then try reversing the soft seat (although it should seat either way). Lastly, make sure the needle spring tension is adequate enough to keep the...

Norm, If the spring is holding the needle against the seat, the seat has to be the problem. I would replace the entire rubber seat assembly. Jeff

Norm, If you have gas leaking out the vent hole in the top cover, you have a hole in the diaphragm. Replace it. If gas is leaking at the outlet port of the regulator, the needle valve/seat is the problem area. If it is in this location, use a depth mic to check the bored .355" dia. hole depth...

Luc, You could be right. When I was looking for this very information many years ago a model builder told me the lip side was the needle seat side. That model builder's engines ran nicely so I have built all my regulators the same way, and mine all run fine. Hence, my recommendation. I'm not...

Norm, The neoprene seat should not be loose in the hole. It should be an interference fit enough to self seal it from leaking. If so, No 2 Permatex should seal it. It is also possible that the spring hole depth is too deep not allowing the spring tension to hold the needle firmly against the...

Norm, The spring loaded valve seats against the grooved lip side of the soft seat. Press it in place with a flat ended piece of full diameter shafting so as not to mar the seat lip. The diaphragm metal center with the little doughnut side seats against the projecting valve needle. Don't forget...

Thanks for the compliments guys. Coming from other builders, they are greatly appreciated. It's nice to have a forum like HMEM to share our efforts and ideas. Jeff

This is my finished 25 hp Bates & Edmonds 17kw model electric plant in 1/8th scale. These unusual looking OHV engines used eccentrics and pull rods rather than cams and push rods. This valve arrangement was known as the “alligator link” valve motion. The full size engines used two built in...

Mfrick, While I am quite pleased with the B-M alternator it is not ideally suited to a model engine in the 500-700 RPM range for which it was designed. It is better suited to much slower RPM engines due to its rather high output voltage at 500-700 RPM. I suppose I could use a transformer to...

Something else you might want to consider. Gear pumps are relatively simple and easy to make. They work especially well on non-pressurized model engine flows and temperatures. Jerry Howell's design is a great performing pump. Gear pumps move coolant with relatively little effort and volume can...

Rolland, Very nice looking engine and generator. Try looking at the O or G gauge model railroading accessories for model street lamps. They are usually 18v, but bulbs of all socket sizes and voltages are available on the internet. Also, street lamps aren't too difficult to make. Regarding your...

Peter, I'm not that experienced at making valve cages, but have had good luck so far as follows. Turn the OD to final dia. Drill the valve cage internal diameter, then drill the stem bore about .015" undersize. My stems are usually .125" so I then bore them a few thousandths more using a...

I doubt your cylinder is too smooth. Usually after finishing with a Sunnen hone rebuilders will run an oiled Flex hone through the cylinder a dozen strokes or so to take off any sharp peaks left by the Sunnen hone finish (plateau honing). Like Dave said, it is a good idea when you are gapping...

I'm with George. Valves are often the culprit. Find a good way to check them. Also, I try to keep the ring land to ring side clearance to a bare minimum. .0005" to .001" is what I try to maintain on a new piston. The ring still has to be free to move in the groove so a good ring lapping to fit...

Hi Grapegro, I use propane on 1" bore slow speed (600RPM) engines. Standard RC carbs are satifactory. The needle valve needs to be opened significantly more turns, but they work well. I use Weber "Go Anywhere" portable gas grill regulators (Ebay) on the disposable 1 lb propane bottles commonly...

The radiator is a standard 120 mm radiator used by the overclocking computer gamers. There is quite a selection now of these radiators. Mine uses a 4 speed cooling fan powered by the the engine driven alternator. Jeff

Dougie, Gaseous fuels are more susceptible to leaning out on increasing speed when using a carb designed for liquid fuels. However, these carbs are often the simplest and easiest to use with propane. The jet and needle are too small ideally for propane, however, the right kind of liquid fuel RC...

If you can tell us what type of engine you are going to use propane on it would help a great deal. I use propane on most of my engines, but they are all constant speed engines. Jeff