Sounds like a fuel starving condition, may be a bit lean on both high and low. For the vibration issue be sure to balance the prop. The smaller Chineese engines are finicky and a small tuning adjustment makes a huge change so you may have to start over from the recommended settings and work your way back. Tune for max RPM on the high and richen it up by knocking 150-200 RPM’s lower for break in, was always my rule of thumb. Even if it was a bit dirtier, the transition and operation were more more reliable. This also keeps the heat down while your ring is breaking in so you don’t have an overheat and stall situation.

Definitely not lean as once you go to factory settings it is soaking the plug. It has to be leaned out just to get a reliable idle. Adjusting high first using Terry method doesn't work as the low end is still way off. Everything is balanced including prop, hub, and spinner.

Make sure you get an NGK plug for it (4383) ME-8. You might be lucky to find a package of these at Autozone for much cheaper than the hobby places. It sounds like if the prop is balanced and it’s shaking that bad, it could be spark or timing. Be sure to gap the plug properly too. It sounded like if the gap was too large on these plugs you might have an issue. You will definitely have to run it a bit rich until broken in, but you might also want to look into a high quality spark plug. Hope this helps.

And check for air leaks in your lines and connections too. I had a Sullivan tank give me a whirl of trouble once, and it turned out I had tightened the tie wire so hard I cut the tygon and the barb wasn’t completely soldered. Since then I’ve changed to a Fourtitude or Kuza style tank with better plumbing than my own.

I am running the Fortitude tank. I have a NGK CM6 plug gapped at .020. I balanced the prop, spinner, and hub. The vibration is terrible unless the low end is leaned out a lot. You can adjust the high for max rpm but it changes a lot once the low is leaned out to get the idle smooth and somewhat reliable. I checked everything so far to include all new gaskets for the carb and the spacer, checked the metering valve in the carb with the Walbro tool, and replaced all the carb gaskets.

Originally Posted by mark071704

I am running the Fortitude tank. I have a NGK CM6 plug gapped at .020. I balanced the prop, spinner, and hub. The vibration is terrible unless the low end is leaned out a lot. You can adjust the high for max rpm but it changes a lot once the low is leaned out to get the idle smooth and somewhat reliable. I checked everything so far to include all new gaskets for the carb and the spacer, checked the metering valve in the carb with the Walbro tool, and replaced all the carb gaskets.

If you try to lean a single cylinder 2 stoke engine to get it smooth, you can do that, but it's NOT going to run right when not idling. They are lumpy. They are NOT smooth like a V-6 or a V8. It's just not in their nature.

To run right, they need to be slightly rich. They'll start easier, and they won't quit if you run them that way. Lean engines are notorious for quitting in the air. They always have been.

If you're running the engine mounted in a plane without the wing on it to help stabilize it, they'll shake all over the place - that's normal!

If this is a smaller engine, say 35cc's or less, a lot of guys run their plugs at .025" or so because they seem to burn the rich mixture better, with a very noticeable difference in the mid range while in the air.

If the idle is left running rough it is so bad that it jumps from 2000 to 2400 rpm creating so much vibration it snapped my hinges on the elevator even after replacing them with Dubro Hinges. My DLE20 idles perfect. That is one of the main problems with this engine is the terrible vibration.

Sorry, but in my modeling career of, well, a very long time, I've never heard of a hinge snapping due to engine vibration.

This hinge that "broke". Is it a pinned type hinge, or a CA type hinge? Can you describe this failure better? What "broke"?

Are you running this engine on a model without the wing installed? What plane do you have this mounted in? Do you have flying wires installed on the stabilizer? I've done that on quite a few of my planes to cut down on the shaking. Some types of construction need that kind of help more than others. The "slab" type seem to need that more than the airfoiled/lifting type.

Also, the "factory" needle settings mean nothing. They are suggested only as a place to get the motor started. Once it's started, you are expected to tune the engine as necessary for YOUR conditions. Note that a lot of time spent getting a "perfect" tune on the ground is a complete waste of time as 99% of the time that tune is going to go out the window as soon as the plane's tires leave the ground.

Last, please understand this engine has been around for quite a while. It is not an engine that's generated much in the way of complaints. Just the opposite actually. It's made a lot of friends over the years. -Al

The CA hinge on the elevator was split right in half so the elevator was able to balance up and down. There are 3 on each side of the elevator. I glued a new one in and had one on the opposite side split the exact same way. It also broke a robart hinge on the flap as well and I had do drill it out and replace it. I then bought a brand new elevator and used dubro hinges. One of those also split the exact same way from the vibration. Now I am in the process of installing a new stabilizer but did not install the elevator yet because I want to get this vibration issue fixed first on the test stand prior to installing it to make sure it doesn't break anything else. It is installed on the Valiant 10cc. I have never run the engine on the plane without the wings installed. In fact, the Dubro Hinge broke from the vibration after approximately 15 minutes of flying with the engine installed after Tom from Valley View RC stated it was tuned and fine to install it and just fly. That is when it was still breaking up badly in flight and dead sticked after 3 minutes of flight. Attempted to retune at the field and had 4 more flights but just couldn't get it dialed in. It was either too rich or too lean. All flights were done with cowl off.

Originally Posted by kingsflyer

You didn't mention a specific brand of 4-stroke engine, but I've found the Saito FG gas engine manual to be helpful.

https://www.horizonhobby.com/pdf/Sai...nes-Manual.pdf

The FG series of engines have a rather specific and unusual break in procedure that must be followed to the letter or major engine damage could occur fairly soon. Don't ask me how I know, but breaking the con rod pin off the crank and breaking the con rod in two and seizing the engine when running at full speed is not a pleasant occurrence.

Even though these engines have a "pump" carb, it is NOT a Walbro by any means and they are still somewhat dependent on fuel tank position relative to the carb centerline.

Whenever I have trouble setting one of my FG gas engines, I still come back to this thread and go through the basics and usually have a great result.

McD

My engine is Valach VM 60.

I picked up a plane that was an ARF and already set up for glow. I am converting it to gas but the tank that I have, has two outlets on the top and one in the cap. I see that the tank in your picture is facing the front of the plane. Can it face the other way?
I also noticed that your battery pack is on the engine box, would heat be an issue.
Should there be two battery packs, one for the ignition and one for the servos?
Thanks

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Posting a couple of pics of the plane and tank and such of what you have would help those whom can advise. Like they say, a picture is worth a thousand words!

The plane is the Great Planes P-6E Hawk from 2006. I thought about it and understand why the tank needs to sit with the cap forward. Hate to make a hole in the plane but no other way to see the tank without pulling the lower wing off. No way to see when the tank is full or empty.
It is the 76" wingspan ARF. Picked this up a week ago still in the box and never opened. Gave $150.00 for it and it came with a new .75 glow but I am installing the DLE 20cc gas.


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Like most planes the tank is full when fuel runs out the vent. Because gas engines have fuel pumps and will tolerate long lines,
you could mount a tank with the cap to the rear but that would be rather unusual. I can’t think of anybody that would recommend that when there is no need to do that.

Originally Posted by Truckracer

Like most planes the tank is full when fuel runs out the vent. Because gas engines have fuel pumps and will tolerate long lines,
you could mount a tank with the cap to the rear but that would be rather unusual. I can’t think of anybody that would recommend that when there is no need to do that.

Thanks. I got the tank issue worked out and mounted correctly. This is my first gasser so having to learn a bit. Going to run a 15 X 8 Master air screw prop. How do I determine the spinner size that I need?


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