I finally had time to head out to the field today with hopes of getting my new mid star 40 in the air, after it sat on the dining room table for a month looking pretty. The wind refused to die down, so I decided to just head to a nice quiet spot near my house and do the engine break in on a supertigre .51. (I'm not a club member and didn't want to do anything at the field without permission).

So I got the engine started and as per directions left the glow plug driver on while increasing throttle to full and waited 30 sec. As soon as I removed the driver, the engine speed dropped significantly. I didn't even have to hold the plane at full throttle. I'm assuming this means the plug is bad, but it's the one that came with the engine so I wasn't too surprised. When I noticed that I forgot to bring a spare, I decided to just let it run the way it was. I didn't bother tuning it while it was running like that, but did run 2 tanks through it using some sig 10% fuel with 25% castor. Very slopppy running stuff, but I figured the engine would enjoy it during the break in period.

What I'm wondering is does this count as break-in time or should I still run a few tanks through it with a better plug before flying?

from my experience, when an engine turns off after the ignitor is removed , its usually too rich.... if not then i would suspect the glow plug

It's sloppy running and slow. That means it's very rich. That's not a problem with the plug. It's a ringed engine, so running it like you did isn't necessarily bad for it.

Where are you flying at? I fly down in Dakota County, at a county park. There's no club, which is a perk in my mind.

I've been slowly working on finishing up a Mid-Star. Well, if you count 8 years of it being unfinished as finishing... I finally have some time and interest, so it'll likely be done in two weeks. Right now the dust must outweigh the airframe!

Thanks for the replies guys. MikeL, I'm planning to join the grassfield rc club in brooklyn park. It's a nice short drive and one of my favorite burger places (culvers) is nearby so I'm already in the area frequently. I thought about checking out the dakota county field too, but that'll have to wait until I've had some flight instruction to work on proper landings. After all the time invested in building the thing, I don't think I could take crashing it like I do my foam super cub. That thing is no big deal... Just about anything can be fixed with a little packing tape and gorilla glue.

So back on topic, sounds like all I need to do is lean it out and it'll run normally. I was afraid to mess with the valve with it running so poorly (almost no change between idle and full throttle). Hopefully I'll have time to give it a try tomorrow.

Oh, and while I'm here, why not show off a bit. The pics are a little fuzzy, but that helps hide the monokote wrinkles.

http://smokey.moxiecolo.com

what are you doing in this pic? http://smokey.moxiecolo.com/main.php?g2_itemId=39

Rounding off the edges of the hatch cover. Seems like 1/2 the build was sanding...

It's been a few weeks, and finally had time to get to the field and give things another try. After bringing the plane to the field and getting some help with tuning from my instructor, the ST .51 is still running funny. He got it tuned nicely and it now starts pretty much every time on the first try. And when removing the glow plug ignitor it sounds good now. But within a few seconds to a minute, it dies. The high and low speed needles both seem to be about right, as things are great with the ignitor on. I did notice that I had to turn the heat up a bit on the panel for the plug ignitor while tuning to keep it running smoothly, though I'm not 100% positive that the knob on the panel hasn't been touched since it was used last.

I'm still using sig fuel with 10% nitro and 25% castor (haven't quite finished the gallon yet). And the stock glow plug is still in the engine. My instructor suspected that the issue might be with the fuel or plug, but wasn't sure and suggested asking about it again on here to get some more opinions. There doesn't seem to be any air leaks, though I plan to replace the fuel tube tonight anyways to be sure and I'm getting rid of the perry remote needle valve (I'm a chicken around a moving prop) to rule it out. And the fuel tank is as high as it can possibly get, though not quite even with the carb. I'd say the opening on the tank is 1/4 to 1/2 inch below. Any advice is greatly appreciated.

If the engine has almost no break-in (my trusty old ST-51required lots to be reliable) that may be the problem.
Is you fuel good?
Glow plugs usually fail fairly rapidily in new engines as they pick up the fine metal discarded by the engine as it seats in.

All of my SuperTigers seem to need to run richer on the low end than I would normally assume or ever set.

This causes them to idle very roughly and to load up when on the ground, but the transitions then are perfect.

So the engine tends to be very rich at idle, and removing the glow plug normally does cause the RPM's to drop percipitously.



If I lean the engine out to fix the idle, the transitions become fairly bad.

Adjusting the aperture using the two screws & turning the entire assembly doesn't seem to help at all.


There was an article in RC Sport Flyer Magazine about easily fixing things like this...


In their example they fixed a TT .46's transition/idling problems by filing a round "edge" hole on the carb barrel, so that more air is introduced at extreme low idle.

It seems like a very simple solution, but I have yet to try it.

why do you add stuff to your fuel to create more gunk ?

Why do you buy higher nitro content fuel and dialute it with oil ?
Why not just buy lower nitro content fuel to begin with ?

I mean, if you go to the trouble if trying to prevent wear and tear on your enigne..then crank it over after a crash...what's the piont ?

Yes plugs are expensive. Generally i replace the plug after a break in or use a break in plug...if it last.lol
I also use plugs with idle bar for break in. It helps a little bit in preventing particles from hitting the coil and killing the plug.

Thanks for the advice guys. I'm going to do a little more breaking in tonight, and then swap the plug for a fresh os #8 before testing again. I'll also richen the low end a bit to see if that helps.

Flyx: I didn't add anything to the fuel man. Sig sells the stuff.
[link=http://www.sigmfg.com/cgi-bin/dpsmart.exe/ProductsV5.html?L+Sig+gfyc5611+_Ddp_5fSearch1_02a4 1FuelSigChapAlCast_01Search_02Index_01SubMenu_02No ne_01Menu_02CatProd_01Thumb_02Fuel_20_2d_20Airplan e_01]Check it out here[/link]

My G-61 ringed engine broke in fairly quickly last fall. Three tanks on the ground and it was reliable enough to fly without worrying about deadsticks.

I found that it liked a hotter plug, however. The Super Tigre plug that comes included isn't a bad plug. It's a medium heat plug, however, and doesn't offer the best performance. With 10% nitro fuel, you might find that an O.S. A3 is the right choice for better idle and smooth transition.

With regard to the engine dying after a few seconds to a minute, I'd pay very close attention to how hot it's getting. If the engine is barely warm when it dies, it's not likely to be an air leak. That would be more indicative of a rich setting on the low end. If the engine is very hot when it dies, then you probably have an air leak.

On a newer engine, just because the tuning was spot on a few tanks of fuel ago doesn't mean that it's correct now. Glow engines tend to continue to break in little by little over time, and a good low end setting now will be too rich two or ten tanks of fuel in the future.

The last thing to consider is your oil content. 25% all castor is a wonderful choice for the first couple of break-in runs on the ground. Once you get done with the basic break in on the ground, however, you're just robbing yourself of power. 18% to 20% oil content is plenty once the first two tanks of fuel have been run through a brand new engine. 25% all castor fuel is normally only used in 1/2 A or plain bearing engines and is too heavy on oil for a normal ball-bearing 2-stroke.

I'd guess that your engine isn't hot when it dies after running for 30 seconds or a minute. I'd guess it isn't even warming up that much. If I were you, I'd get some 18% oil content(all castor or blended, but not 100% synthetic lubrication), 10% nitro fuel and run that with the current plug. If you're still not happy with the results, then go to a hotter plug like the O.S. A3 or the Fox Miracle plug. From there, you should be able to adjust out any minor tuning issues by adjusting the low end needle after re-peaking the high end needle then turning it rich of peak by a quarter of a turn.

Changing the fuel will affect your tuning. Changing your glow plug type will affect your tuning. These adjustments will take a little bit of work and an experienced hand will make easy work of it. If a flying buddy is handy, get together and get a little help. Even two guys with the same amount of engine tuning experience are better than one; sometimes we get frustrated working with engines and a fresh perspective will often help.

Good luck and let us know how you fare!

Heh... which also permits a richer setting at idle too.

You have a good mix for break in but 20% is usually plenty for oil content. Run a few tanks of what you have through it then change the plug. If that is no help purge all the old fuel out by borrowing a 1/4 tank and run it out then borrow a full tank and re-adjust.
I spent a whole day adjusting a carb with bad fuel and all I got was Fustration. We all hve been there. Just for peace of mind CLOSELY inspect your tank set up in side and out. STUFF happens

It is also worth while to pull the needle valve out and blow some fuel through then replace the needle valve. Check the tip for defects dirt etc. this is also a good time to add a small piece of fuel line to prevent air leaking around the needle valve. Always watch for a short pulse of air bubbles when adjusting the needle valve. This would indicate an air leak around the O-ring...don't ask how I know