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DL 50 low compressions, low power, bad idle

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DL 50 low compressions, low power, bad idle

Old 07-25-2009, 11:08 AM
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Cambo
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Default DL 50 low compressions, low power, bad idle

Ever since my DL50 was new it had low compression. It has always been hard to start, and it just doesn't seem to be getting any better. At this point, getting the low end to run smooth and transition well makes it impossible to start. Its idle has never been good and now that i recently acquired a cheep little spe 26cc that idles like a champ, i feel like there is something wrong. Compression is much lighter than all other 50's at the field. I broke it in with echo at 32:1 and have run it ever since at 50:1. Power numbers just aren't there. The most i can squeeze out of a 23-8 is 5700rpm. The most i ever got out of a 22-8 is 6600 Yes it is hot out and has a pitts muffler but i feel like something is wrong here. It has 20 gallons and is coming up on 2 years old. Any thoughts? Purchased from DLUSA.net
Cameron

Old 07-25-2009, 12:19 PM
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HATH
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Default RE: DL 50 low compressions, low power, bad idle

It may be a shot in the dark... But the first dl 50 and 100's all have low compression. after break in mine run best on a 44:1 oil mix. With the low compression the engine really likes the oil and is sensitive to the mix ratio.
Old 07-25-2009, 12:34 PM
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Default RE: DL 50 low compressions, low power, bad idle

I'd pull the jug off and check to see if the ring is stuck. If it's not stuck I'd call DLUSA and see what they will do for you. Did you ever check the timing?
Old 07-25-2009, 09:48 PM
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CHRISTANEAGLE
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Default RE: DL 50 low compressions, low power, bad idle

Cambo try calling DLUSA and see if they will offer any help. If you are like me you want rest until it's right. You can pull the muffler and take a look and see if anything jumps out at you. My low compression issue resulted in a total rebuild and it was just a little older than yours but, about half as much time on the engine.
Old 07-25-2009, 10:16 PM
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Cambo
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Default RE: DL 50 low compressions, low power, bad idle

I just had the entire engine apart and didn't notice anything obvious. These numbers have been relatively consistent with the three different mufflers on it through the entire time it was running. I haven't checked the timing but there doesn't seem much room to change it. I will pull the jug off and see what i can do. Unfortunately, i am not going to be around the plane until Thursday.

Edit: Few more questions
Is there any trick to taking the head off other than removing the 4 screws and pulling it off.
Also, what is a stuck ring?

Old 07-25-2009, 11:44 PM
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Default RE: DL 50 low compressions, low power, bad idle


ORIGINAL: Cambo

Is there any trick to taking the head off other than removing the 4 screws and pulling it off.
Also, what is a stuck ring?

No, four bolts and it's off.

The ring should be free in the ring groove. If it's stuck in the groove it will look like you can put it right back in the jug, if it's free it will be sticking out of the groove and you'll have to kind of press it in to the groove onto the alignment pin to get the jug back on.
Old 07-26-2009, 12:42 AM
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Default RE: DL 50 low compressions, low power, bad idle

If it's stuck the ring will likely only be stuck on the exhaust side of the piston. So half will be flush with the side of the piston while the other side will be sticking out the side of the piston. The rpm you describe sounds more like a timing issue. Worth checking and easy to do. Check www.ch-ignitions.com for a timing protractor and instructions.
Old 07-26-2009, 09:37 AM
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Cambo
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Default RE: DL 50 low compressions, low power, bad idle

Can fiddling with the timing really change it that much. I mean there isn't much room on the DL to change the timing at all.
Old 07-26-2009, 09:53 AM
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Default RE: DL 50 low compressions, low power, bad idle


ORIGINAL: Cambo

Can fiddling with the timing really change it that much. I mean there isn't much room on the DL to change the timing at all.
A world of difference. 30* difference in timing is about 3/8". Do you need help timing it? I have a no math way if you're interested.
Old 07-26-2009, 10:44 AM
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Default RE: DL 50 low compressions, low power, bad idle

Checking the time can tell you if the hub slipped on the crank after a wicked prop strike or a crash. It would have to be way off. And you're right there's not much room for the sensor to move.
Old 07-29-2009, 04:37 PM
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Default RE: DL 50 low compressions, low power, bad idle

So i just got back. Haven't touched the engine yet. Math doesn't scare me but i don't want to be purchasing a bunch of tools for this. I had a prop strike at idle WAY back when.
Something i would like to add, this engine needs an abnormally lean low end to fly well. Only one turn out, could this be related to timing,

Cameron
Old 07-29-2009, 05:30 PM
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Default RE: DL 50 low compressions, low power, bad idle

A full turn out on the low end is not lean. For many engines that would be quite rich on the bottom. Hard to slip a hub on a DL. You'd have to break something for that to happen. However, you could have bent something.

Having incorrect timing is unfortunately a common issue with all the engine makers. I suppose it depends on what kind of day the person is having, or the night they had before, that is setting the timing. Checking and setting timing is a relatively simple process. The big tool is available free in downloading at [link]http://ch-ignitions.com[/link]. You'll have to provide your own wire and clamp, along with a little work in making some type of backing for the protractror. You might end up making the sensor bracket slots a little longer than they are.
Old 07-29-2009, 11:05 PM
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Default RE: DL 50 low compressions, low power, bad idle

My DL50 came from the factory with the timing at 39 degs. It ran OK at full throttle but idled and transitioned horrible. It wouldn't idle very slow at all without popping and just quiting (sometimes it did it at 1/4 throttle or more). Maybe 2200 on a warm day was about the best idle it would do. I moved the timing back to 28 degs (I had to slot the hall effect holder some more) and it's a completely different engine. Idles great all the way down to 1300 (it will idle below 1000 but it isn't consistent that low), transitions great, and starts way easier than before. Compression got better with each gallon until about 6 or 7 gallons and now is just as good as my nephew's DA. First start of the day takes four flips to prime then choke off and one flip start every time. After the first flight she starts first flip every time just turning the swith on and flipping it. Before I set the timing back I thought I had bought a piece of junk but she's turning a 23X8 XOAR beechwood 6800 on a 98 deg day here in Houston.

Get with Bob at DL and see if he can make it good for you. They are great engines when they are right. Also, the low needle on mine is just over 1 turn out. Maybe like 1and1/16 to 1and1/8 out. The timing change made my low end easier to tune for some strange reason.
Old 07-30-2009, 11:47 AM
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Default RE: DL 50 low compressions, low power, bad idle

So I checked the timing and it came in right at 28 degrees. I did it 3 different times and every time got the same result. So i decided to take the head off. I am not really sure what to think of the inside. It is carbon caked. There are botches, particularly around the spark plug and on the piston that are very thick. Thick enough that just rubbing it with my finger removes most of it

I am thinking this could be related to it being run rich on the low end for most of its life (i just recently figured out how to get it to run smooth on the low end). I am really not sure what to do from here. Maybe clean the engine out and put a new ring in and start over.

Cameron


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Old 07-30-2009, 11:54 AM
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Default RE: DL 50 low compressions, low power, bad idle

Also would like to add that the ring is not stuck
Cameron
Old 07-30-2009, 12:07 PM
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Default RE: DL 50 low compressions, low power, bad idle

That's a good place to start, might think about a new piston and cylinderas well. If you have the means take measurements of the piston, cylinder and ring, I can help you interpret yourfindings if you wish.Deffinately need to change oil, tuning or both.
Old 07-30-2009, 12:27 PM
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Cambo
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Default RE: DL 50 low compressions, low power, bad idle

Unfortunately, i don't think i have a good way of measuring it. I really don't think i have the funds for a new cylinder and piston currently. Most of my RC money has been drained into RC helicopters this summer. Nobody do rc helis, they cost too much and are soooooo addicting .
Old 07-30-2009, 12:44 PM
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Default RE: DL 50 low compressions, low power, bad idle

That looks very much like what Lawnboy does to an engine. I agree with Jody. A good clean up, a new ring for certain, possibly a new top. Just for comparisons, here's a picture of a 500 hour piston run at 50-1 in good tune.
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Old 07-30-2009, 12:44 PM
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Default RE: DL 50 low compressions, low power, bad idle

Boy that's nasty looking.

If it where mine I would:

Take some K1, or gas if you don't have K1, and wash the piston top and sides, do the same to the jug, get as much carbon out of it as I could.

I would then scrape the piston top with a #11 blade drawn backwards over the carbon, getting as much carbon off as I could, then clean the exhaust port as well as I could.

With the K1 or gas I would clean the sides of the piston using a scouring pad, then do the same for the jug.

I would then take 1500 grit wet/dry sand paper and give the inside of the jug a light de-glazing. Turn the jug with one hand while de-glazing using the paper with the other, any "sanding marks" should look crosshatched. This last I wouldn't do too much of 10seconds should do it. Rinse everything with the K1.

Reassemble.

Get PENNZOIL AIRCOOL oil.





Old 07-30-2009, 01:08 PM
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Default RE: DL 50 low compressions, low power, bad idle

soarrich, that sounds like a good plan. I am also going to replace the ring.

Cameron
Old 07-30-2009, 01:10 PM
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Default RE: DL 50 low compressions, low power, bad idle

Also, do you think I should go with the stock ring or a bowman ring

Cameron

Old 07-30-2009, 02:41 PM
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Default RE: DL 50 low compressions, low power, bad idle

I'd run down to the auto parts store and obtain same chemical carb cleaner dip. Drop the hard parts into it for an over night soak. Most of what's there will be dissolved by the next day. Then I'd use a very stiff nylon or brass brush, or Scotchbrite pad to remove any residual deposits. Rinse with water, blow dry with a compressor, then coat everything with some mix oil. I would not use any abrasives inside the cylinder. If there is a loose ring to cylinder fit now, it would be worse after using an abrasive. Plus you have the issue of abrasive grit getting into places you would not want it to be.

I would use a stock ring. There will be no benefit to using a Bowman ring in this instance. I have some new DL 100 (50cc/side) rings that I can't do anything with since I switched to a 111. Jody might get a little ticked (he'll get over it) but if you can wait till next week I could mail one to you. I have to get back to where the rings are...
Old 07-30-2009, 02:55 PM
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Default RE: DL 50 low compressions, low power, bad idle

Hi Tired Old Man
That would be awesome, when do you think you will be getting back next week.

Old 07-30-2009, 03:05 PM
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Default RE: DL 50 low compressions, low power, bad idle

Cambo first good luck!!! hope you get you engine running again soon. Can you tell me which oil did you use all this time?.

Best Regards,
Old 07-30-2009, 03:58 PM
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Default RE: DL 50 low compressions, low power, bad idle


ORIGINAL: Tired Old Man

I'd run down to the auto parts store and obtain same chemical carb cleaner dip. Drop the hard parts into it for an over night soak. Most of what's there will be dissolved by the next day. Then I'd use a very stiff nylon or brass brush, or Scotchbrite pad to remove any residual deposits. Rinse with water, blow dry with a compressor, then coat everything with some mix oil. I would not use any abrasives inside the cylinder. If there is a loose ring to cylinder fit now, it would be worse after using an abrasive. Plus you have the issue of abrasive grit getting into places you would not want it to be.

I would use a stock ring. There will be no benefit to using a Bowman ring in this instance. I have some new DL 100 (50cc/side) rings that I can't do anything with since I switched to a 111. Jody might get a little ticked (he'll get over it) but if you can wait till next week I could mail one to you. I have to get back to where the rings are...
This is exactly what should be done if you reuse the old parts, my only concernwould bewith your description of low compression from new and never improving. Without proper inspection by experienced eyes you may have exactly what you had when it was new, low compression due to a problem with the cylinder for instance that should have never reached the consumer in the first place.

Regardless, you can't hurt anything by doing this and your new ring would be able to be reused in a new jug if it wasn't run for more than a gallon or so. BTW, if you do have an undesirable anomaly in your cylinder and then go at it by hand with sandpaper it will only make it worse than it was before. Sandpaper,...... bad.

Now I have to eat beans and hotdogs for rest of the week, if I could only sell a couple more rings......

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