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Sounds like too much blowby. I would remove the cylinders and the rings from your pistons and give your rings the Mayhugh test. Make a stepped plug with an OD slightly larger in diameter than the inside diameter of your compressed rings. The plug step should fit closely in the ID of the...

Xander, Propane fuel would likely require a wet sump for lubrication of the cylinders and the crankcase interior. Propane provides very easy starting, and reduces exhaust odors. It also keeps the combustion chamber area very clean. I can’t say that for a wet sump crankcase though. Propane...

Just a suggestion to think about because I am unfamiliar with the carburetors you are using. When an engine transitions from idle to a faster speed the air flow increases and the vacuum signal to the fuel supply decreases leaning out the engine. If there is no compensating feature in the carb to...

John, You have a very unique and interesting engine design. If this is to be a working engine you might want to consider some added heat under your carburetor. That area may get pretty cold if you use a liquid fuel. Jeff

Xander, You can use a screw-on gas pressure regulator/shutoff valve found on small portable gas cooking grills. This keeps pressure low at about 4" of water column which is adequate. You will need, or you can make a demand regulator which allows fuel to flow only on the engine intake (suction)...

I use Bondhas wrenches and will stick with them. I only buy cup point black alloy set screws from Atlantic Fastener or McMaster Carr. One trick I discovered has proven out for securing cams with two tiny cup point set screws each at 90 degrees. Once you know the final placement of the cam your...

I have to go along with Terry's recommendation of Gun Kote. Grit blast with 120 aluminum oxide grit, wash clean with detergent, then spray it on. I use a cheap air brush at 15 to 20 psi. No primers needed for any base metal like aluminum or brass. If you mess up your paint application just wash...

Xander, The exhaust cadence of a 180 degree crank in a two cylinder engine is definitely different just as it is in an old JD two cylinder engine. Your question about the possibility of firing both cylinders simultaneously with a wasted spark ignition is valid. Just looking at the condition in...

Set screws do have limitations. Binding can easily exceed the limits on non marring small set screws. Other methods such as Dykem should be used first to detect the source of binding. Never try to "run-in" any engine with serious binding issues. Always finish up with new set screws once...

I know the problems you are having. Bin there. You cannot rely on a smooth surface friction fit with no marks in the shaft for anything but light fitting. Even light wrench torque on a good hard set screw will cause burrs. Relieve the shaft .010"-.020" as advised above. The standard cup point...

Eccentric, It appears you are using a radiator designed for computer processor cooling. Unlike engine radiators they were designed to handle very low delta T (approx. 10⁰ F) across the radiator. Indoors a model engine can use a radiator with a 90-100⁰ F Delta T so they are very effective at...

Doug, You have an excellent runner. Congratulations. May I suggest that you don't forget to add a gear guard to your engine before too long. I couldn't tell the rotation direction of your engine, but accidents can happen in the strangest ways. Your carburetor problems with propane are common...

Ken, The long rods do not work on the push stroke. They work on the pull stroke. You first adjust the angle of the top valve lever nominally by guess until till you get a near 90 degree angle between the pull rod and the top lever to maximize mechanical advantage against the valve spring torque...

Bill, Yes the alternator will do 36 watts but is limited by the 3 amp voltage controller. As an alternator only it could be rated for 55 watts if I could find a suitable voltage control. It is a capable alternator, but it is not efficient due to its solid rotor. My goal has been to demonstrate...

Bill, You are correct, power does not scale linearly. The 1/8th engine scale of this model refers only to the engine component dimensions. When the dimensions of an engine are scaled down to 1/8th of the original engine size the model engine displacement reduces by the cube of the scale. This...

Ron is right. The problem is combustion blowby gases which are moisture laden and quickly condense in a cold crankcase. It is best to run your engine each time long enough to get it fully warmed up internally. Unfortunately it starts all over again every time you start it cold until you get the...

Gordon, I use propane and try to keep it simiple. I use a Weber Go Anywhere gas grill 1 lb. bottle regulator. It's a constant pressure (~ 4" water column) adjustable flow regulator. You don't need much pressure. I use Jerry Howell designed demand regulators. I try to find self compensating RC...

For the DIY belt makers here is an option...

I have a number of throttle governed multi-cylinder model engines operating on vapor propane. They all normally start in one or two spins of the flywheels, no cylinder carbon build up, will not flood, near odorless, and are in my opinion safer to operate at shows. And, propane is very economical...

Brownells sells a water based anti scaling coating that I have used with success. Its hot working range is 1000 -2300 F which is probably close enough to your heat soak range. When used the rings come out a uniform gray color after washing in hot water. Jeff