jedijody

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Ok, here's the pictures. Basicaly, everywhere the ring traveled there is a bunch of wear, especialy considering the low time on the engine. In the pictures of the cylinder you can see a line all the way around the jug where the bottom of the ring travel is, at that point the cylinder grows about .003" in diameter, there is a definate ridge that can be felt with your finger.

The ring is very worn and the end gap at the bottom of the cylinder where the ring has never traveled is almost .020" above the ridge in the ring travel area of the cylinder the gap jumps to .025" and gets bigger towards the top. Also, the bottom of the ring has a definate ridge where it makes contact with the piston, you can see the shiny line then the dark perimeter of the bottom of the ring, this is the ridge and again is very obviously felt with your finger nail.

The piston looks decent considering, I guess the extra oil and overly rich needle settings helped float it off the cylinder, it could be reused but not in a new jug with a new ring. I think the excess carbon in the cylinder acted like a form of very fine lapping compound that gradually wore everthing beyond the point of no return.

When you calculate out the initial fuel mix the way it was explained it works out to be about a 4:1 fuel to oil ratio for about 1/2 a gallon. No matter what oil it is that's a good start on carbon build up, the rich needle adjustments took over from there to make what you see in the pictures.

Thanks Cambo for sharing your learning experience, I'm sure it may help prevent someone else from making the same mistake.

Cambo

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Edit: got the pm

Great pics, thanks for sharing BTW

Cameron

Tired Old Man

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I've got a cylinder assembly here from another manufacturer that is in similar condition, although the cylinder increases in diameter roughly .005" from bottom to top of the stroke. These things happen once in awhile.

Cambo

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Once I get the parts I am wondering if there is a good ground break in procedure so i don't have to burn a good day of flying doing circuits.

Also, should the piston and ring be reinstalled with some kind of oil.

Cameron

jedijody

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Make sure everything is super clean and assemble it with a little of your 2 stroke oil that you put in your gas.

Although I do run a couple tanks on the ground or stand before I fly an engine a complete break in process is much to long (several hours) to do on the ground, it would require near constant attention of varying the load, RPM, monitoring temperature, and starting and stopping, etc. It's much less tedious to do in the air flying your plane, trust me, and your neighbors will thank you.

You don't need or even want to just putt around the pattern at 1/2 throttle, fly the plane as you normaly would except; don't lift off, point the nose straight up and climb at full throttle for 2000 feet, hovering is ok for very short periods (10-15 secs., that's all I can do anyway), severly limit or eliminate maneuvers that incorperate full or nearly full throttle with little to no airspeed like waterfalls or flatspins, they can heat an engine up very fast. Fly around and practice some basic IMAC sequences, or practice some gracefull slow rolls and large loops, perfect figure 8s, that kind of flying can be very challenging.

Go through about 5 gallons or so like this and then let it rip.

Cambo

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Ok, sounds like a plan then. Thanks for the heads up.

Cameron

Cambo

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I got the parts from Jody the other day. I was out of town until today and got a chance to put the engine together. I was very careful to get the piston orientation correct and to equally tighten the head bolts. Once everything was together I immediately noticed a drastic increase in compression (had a hard time turning over without the prop installed). My DL has never had compression this good so i was very happy. I put it on the plane and got it ready to start it. I mixed 2 gallons at 32:1. I started flipping and for the first time ever had the engine really effectively sucking fuel with the carb dry. I got it going with 7 choke flips and 3 flips after that. I revved it up (had the needles rich) and peaked it out. I was getting 6250 at first. I then went for the low end and leaned as far as i could go without sacrificing transition. I still had a slightly rough mid range but was very happy. I continued to run the engine around 2800rpm. I went back to WOT and saw the RPM's had picked up to 6300. At the end of the about 35 minutes of running i was getting 6370. So i haven't hit 6400 but i am well on my way. The most noticeable change was the idle. WOW. After about 10 minutes of running i noticed that engine was happily idling between 1300 and 1400. By the end of the first tank, i was getting 1100RPM [X(][X(]. I basically have a new engine. It is turning around 700RPM's more on the first tank of gas, on the same prop (23-8), same pitts muffler, and same 100 degree temperatures (actually turning more RPM at 1/2 throttle as it used to turn at WOT). The idle is close to 500RPM slower than before and very reliable (used to be very shaky below 1800rpm). Have two weeks before school starts and ALOT of flying to make up for.

Thanks so much for all the help everyone
Cameron

JOHNS3D

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Cambo thats good news!!!, i know how frustrate is to have a engine in bad shape(happen to my with a 4 strockes), just be carefull and use good oil(jody recommends Stihl).

Regards,

Tired Old Man

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Might want to finish tuning that engine. Running one rich to break it in is much too similar to what happened before. It has to run through normal heat and cooling cycles while running to break in. Tune it for performance and the rest will take care of itself if you follow Jody's flying instructions.

Cambo

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Maybe i didn't make that clear in the other post. I peaked the high end with the engine running and leaned the low end as far as it will go without sacrificing transition. It is only one tank on the ground and tomorrow i am going flying.

Mikecam

Don't want to start anything with this link. I have not seen it here on RCU before but if it has passed around before then I haven't seen it and possible a few others have not seen it either. I have broken in my 2 stroke and 4 stroke snowmobiles and racebikes and dirtbikes with this method and have yet to have a problem. My motors burn no oil.

http://www.mototuneusa.com/break_in_secrets.htm

Tired Old Man

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The rpm numbers were indicating tht it was still not tuned as well as it could be or the prop is too large and/or loading the engine too much.

I completely disagreee with the moto tune article about heat cycling. The motorcycle engine article does not apply in that area to our little gassers. It presumes the metalurgyu of our little engines is on a par with the motorcycle manufacturers. They are not, and the casting strength has not come together by the time we receive them. There are only a couple of model engine manufacturers that even try to achieve high levels of casting quality and none of them are Chinese.

JoeAirPort

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Yeah Cambo what prop is that? I prefer letting my 50's run up past 7000. They sound very happy running in the low to mid 7000's. I think they run cooler too.

Cambo

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Update
I put 1 gallon through the engine today. WOW, what a difference. Transition is AMAZING, idle is great and consitent, and the power is just that much better. I did exactly what jody described for break in flying.

Please keep in mind everyone that this is using a more restrictive pitts muffler (not the stock muffler), is a 23-8 prop, and it is over 100 degrees. I cross reference my numbers against a DA50 turning the same prop with a similar pitts muffler and 14 gallons run through her. The DA was turning it 6350.

Cameron

JoeAirPort

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With a more restrictive pitts and that prop, your peak RPM number is right on.

Bob Pastorello

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Cam - not meaning to barge into your thread/issues, but having some experience with the Pitts and most 50cc engines....I would really caution against the 23 x 8 at this stage of "newness" on that engine....just my .01 worth, but it needs to "breathe" and heat cycle without LOAD cycle adding to the heating... a 23" is a lot of load on such a new engine. I think it would be healthier, cooler, and happier with a lighter load while it's "young"

Jezmo

Bob, I agree. I ran a 22X8 XOAR on my DL for the first few gallons and then switched to a 23X8 XOAR beech after it was thoroughly broken in.

gildaguz

Does any body have problems with the bearings on the DL 55, i own one that i run all ready 8 gallons of fuel mixed 100 :1 with AMSOIL SABER and 87 octanes gas and i stat feeling some bearing noise

craigteffe

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How do you feel bearing Noise??
At that ratio, and what I have heard about that oil i would say your FEELING rod bearing noise.

Cambo

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Got a mejzlik 22-8 lent to me. It is turning it 7350

Cameron

Bob Pastorello

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THERE ya go!!!!!!!!!!! NOW THAT is how it's supposed to be.....good for you, Cam!!!!

JoeAirPort

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Now that's one happy engine.

Cambo

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I got out to the field today and flew with the mejzlik 22-8 and i am much happier with it. It is hard to believe but the engine idles better with it. It idles just a hair faster, but it is more consistent and doesn't move the light (15.5 pounds fueled) airplane. On top of that, it is much, MUCH, easier to land the airplane. The 23-8 had such a powerful breaking force that it actually was hard to land: too low throttle and the plane suddenly drops like a rock, too fast and you simply cant land. I usually had to do this thing where i would dive the plane down, level out about 2ft above the ground and drop the engine to idle. With the 22-8, it just floats in. Even better is the plane has a harder time torque rolling in hover. With the 23-8 it would torque roll even with full right aileron and 3d rates, making it very hard to hover. Lets not forget the speed though. Currently, the plane is moving faster than ever and the vertical performance is absolutely ridiculous for such hot summer days

One thing i am having problems with is keeping the mounting bracket that TBM wants you to use with there silent beauty pitts mufflers from coming loose. I can't keep the whole I drilled from stripping out and am lost on how to avoid it. I have tried a drill tap and a self tapping screw

Thanks again
Cameron