DLE 35 RA issues
 

Hi all
My son and I both have the 35 RA engines ,mine runs ok so far, His on the other hand has been an issue from the get go, it likes to gurgle between 1/4/-1/2 throttle which as a rule I can either tune out or in this case run a line from the Dia cover to the inside of the fuse to a pill bottle and the problems solved. Not in this case, so here is what all I have done so far, Ran the line, opened up the gap on the plug to .026 removed the spring from the plug cap as it was stopping the cap from seating correctly. Checked the opto kill, checked the on /off switch I have gave the carb a good tuning trying several different methods, non have seemed to work.
Also the engine will just die W/O any warning what so ever, its totaled one plane and did some fair damage to another one because of this.

Let me back up here a little when I said mine runs ok, yes it does gurgle some but so far has not died on me.
Anyway were going to bench run his engine for a few tanks and see if it may be just a tad tight, as a rule I don't bench run my gassers for more than a few ozs of gas on the ground while setting up the carbs and stick them in the air.
Watching of course what I do with them for the first gallon or so of gas.
Any help would be appreciated I can't stand an engine that's out of tune or sounds like it.

First things first, you should be running the NGK CM12 plug.
After that if its not running better come back and report on what's going on.

I have run 4 of these 35's on various planes with no issues so I might be able to help. I've done the diaphragm mod on two engines for a P-38 too. No pill bottle just thru to cooler air on the other side of the firewall.

Chris, I'm curious, I thought the NGK CM6 plug was the standard for DLE, or most other, gassers. I have a DLE 35RA I got from a fellow club member and it has a NGK CM6, but he was having some mid-range burble issues. (I have not run it yet,) You recommended a NGK CM12 plug, I've not heard this before, but I'm interested, why is this a better plug for the DLE 35RA than the CM6?

Bob Mc

Hi Nick Long time no talk,
Anyway I thought that was standard procedure in any DLE product to toss the plug and go with a NGK I'm with birddogs though, I have never heard of or seen a NKG-12 plug, I use the CM -6 in all my smaller gassers .
There is quite a thread on the 35 RA with the same issues that were having so if you got 4 of them to run W/O a hitch I would beat the door down knocking on wood "LOL".
FYI its not the cooler air that stops the engine from gurgling its the constant pressure that's maintained by placing the line on the cover. Some cowls develop quite a high pressure area inside the cowling and actually push the diaphragm down flooding the engine which causes the gurgle.

My bad CM 6 is right, CM12 is two times better! Lol

The burble issues you hear in flight is caused by the load on the prop. If you hear that when the prop unloads on the down leg of a loop it's because the reeds are fluttering. The intake velocity is not high enough so the reeds close.
Ive tested many props and found on the DLE 55RA that the Xoar 22x10 wood or carbon removes the burble. The performance is the best I've seen of all the combos I tried, Top Flite, Zinger, Master Airscrew, Xoar.

if your seeing a burble or hesitation when adding power then you need to tune the carb better. After some run time from new you have to adjust the low end too, not just the top end. Also each day the weather is different so from weekend to weekend you need to see how it runs and make any adjustments necessary.

Fuel: I run 92 octane non ethanol gas at 36:1 with Klotz Technoplate.
I have tried Bell, Honda, Stihl, Golden Spectro, and Cool Power. I went back to Klotz because they run great and don't leave much residue.

The purpose of the mod on the diaphragm cover is to give the diaphragm its own air supply. The cowl pressure can be from heat or high air pressure or both resulting in a stalled pump. So soldering a fitting to the cover and running a tube out to another air source is a solution.
Also if your engine is cowled and its kind of tight then you can add a baffle between the carb and the muffler to block the radiant heat from the muffler. I made two for the P-38 and the diaphragm mod just to cover those bases. Plus I added large aluminum velocity stacks to increase carb cooling. Inside the cowls I baffled the engines too. Fully scale tight cowls and the engines run at 168F at idle. This all worst case scenario stuff but it works.

Ive run one 35 in a Zero and one In a TF Stinson and both run great without baffling or any mods.

What prop are you running on the 35?
Which oil and gas?

they dont quit when they are too rich.. you are probably too rich on the low and overly lean on the high needle.. they interact more than most people think..

I don't get why people with a single cylinder 2 stroke engine, running a carb design essentially unchanged for over 50 years (or longer), get so worked up over burbling in the mid range. That's what they do when unloaded (as in cruise mode). If you pull the nose up to add a load when you hear that, the gurgling goes away immediately. It IS about the load on the engine!

I think most will find that eventually you just get used to the gurgling and leave the engine running on the rich side. It's not hurting a thing, and you'll be rewarded for putting up with that with an easy handling engine that will last a long time. If you try dialing gurgle out with leaner mixtures you might as well get used to the idea of dead stick landing practice, because that's WAY more likely to happen when an engine is set lean.

These are not fuel injected multi cylinder engines. Don't make the mistake of thinking you're going to get it to run like something like that.

Considering that i build alot of my engines from scratch i think i know how to tune a carb. You have changed props to change the load on the engine, which may or may not get rid of a burble but it does nothing for the pressure rise inside many cowlings especially round ones.
The yaks and such are the worst but with the simple tube off the dia cover to the inside of the fuse
solves the issue in most cases. I have done many an engine and used the same prop it was blurbling on and it ran perfect after the tube mod. Just so happens the 35 isnt one of them. Plus its takes quite a lot to stop a gasser in the air and this one just dies W/O any warning.
It almost reminds me of the DLE 30 i designed the new backplate and reed cage for.
Thank you all so far.

Cyberwolf, First thanks for all the info I've learned from you in years past so adding my comments here are a bit like trying to teach the teacher if you know what I mean!

From time to time, we all come across an engine that just leaves us stumped. Sounds like you've met yours with the 35. I know you've ruled out all the possible mechanical problems and that you have a sound engine from that standpoint so that really only leaves ignition and the carburetor as a possible cause. Ignitions have been a source of many problems with these (and many other) engines but most of the problems have been confined to the sensors that will misfire in any number of ways causing a host of problems. I'd replace that first and as always, I'd highly recommend the ones sold by RC Extreme Power. Other sensors work fine too but the ones sold by Milton at RCXP are know to be problem free .... at least so far. If that makes no difference, I'd substitute a new ignition box to see if that makes any difference. If still no luck, I'd start looking at the carb for issues. You probably have some known good carbs there so I'd probably start out by substituting a different carb just to see if the engine runs any differently. The carb doesn't have to be the exact one for the engine, just a similarly sized WT or clone. If that resolves the problem, considering their relatively low cost, I think I'd just buy a new carb for the engine. If a carb problem is confirmed, I suspect there may be some fod floating around in the fuel metering passages and trying to clean those areas out can be very frustrating. If the fod moves to the wrong location, it can cut off the fuel flow. Oh yes, I assumed you've already done all the normal carb internal checks such as screen, proper location and conditions checks of gaskets, diaphragms, metering needle lever height, etc.

I'll be curious to hear what you find. While our engines can all have their own personalities, most of mine run quite well as provided and I do expect good, reasonably smooth performance throughout the throttle range. A bit of gurgling is normal at certain power settings and in certain attitudes but it shouldn't be excessive. In a few cases, I've had to make modifications or substitute carbs to get that level of performance, but that is the exception to the rule. A few engines are nasty by design but the DLE 35 isn't usually one of them.

Just a pet peeve Cyberwolf, maybe combined with not enough coffee. Apologies for posting something like that, with full knowledge it wasn't going to help your issue one bit. Should have just kept my mouth shut. Best of luck figuring out what you have going on. -Al

Al no need to be sorry about anything.
the reason i dont like the burble is i know for a fact it dose not need to be there and still have an engine that runs great never dies andsounds solid through out.
Chris i read about the heat sheilds and thats going to be my next step, thank you for reminding me about it.
Truckracer your words are to kind, i have followed your posts and have gained so much usefull information its not funny.
your correct this is one of those engines that has my back up against the wall.
what gets me is mine runs good so far not any sign of a dead stick and the burble is tolorable after i added the vent line. In fact i think with a little more time on the engine i can tune it so its not there.
i dont have any onboard telemetry to see just how hot the two engines are getting but neither seem to be hot on landing, in fact we ran my sons engine W/O the cowling the last time when it died.
im still leaning its tight on the cylinder, or something is a little out of line.
i could tear it down and check it out but that is alot of extra work and time i shouldnt have to spend.
Anyway guys thank you all for your input on this.

Just curious but which plane or planes are both engines having a problem when installed?
Do these engines have issues on a test stand?
Im thinking the fuel tank or the ignition could be the problem but two of the same engine giving you issues is statistically not realistic from a production standpoint. So in my opinion there's something outside of the engines contributing to their failure to keep running normally.

Maybe go back to basics and look over the installations again. Could be something simple, you never know!

Ok, thanks first off to my dad "cyberwolf" for looking into this further for me, second, the engine has been in two different great planes Factors, first one bit the dust twenty foot off the deck because I was going back and forth doing pop tops "yes I know better with a new engine but wth!" And it landed flat on all the wheels, rebuildable, but thought we would bypass for now and just had another kit shipped asap. On the second plane it would die in a straight line of flight 1/2ish throttle, no cowl on the plane, once landed the engine was cool enough to grab for a few seconds, nothing out of the ordinary so temp seems good. This is also where the burble CW was talking about, so the prop load isn't the issue he was speaking of, they both do it no matter what and yes he can fine tune an engine to neat perfection that people have trave led across the states to have him tune and setup their engines, but any how the point is It is almost like I shut the ignition off, one flip it starts right back up and runs good, so after the cost of two of the Factors, 2nd one didn't deal with its wrestling match with a rock pile very well, but anyways, here are my thoughts, bad ignition? Fuel tank problem "I used the same tank from the first plane since it was it's first flight when it let gravity win", or the plug cap, which in my opinion does not fit correctly, so I'm left here pondering plumbing problems in the tank or my ignition is bad. We have a brand new carb that towers have to me for free, I'm going to have cyberwolf redo my reeds if he thinks it is needed, because I have seen issues with older DLE engine reeds, I'm also ordering a new bowman ring just because I can :-P , thanks everyone is there anything else outside of a heat shield I should consider? No more factors, I'm going with MX2 this time, the factors were fun, but a few issues from the last one's glide habit had made me weary. Thanks all!
​​​

Sorry i have not made it back here to report whats going on with the 35's.
ok mine died twice on me due to an over heating condition.
I saved the plane easy enough both times, so heres what i did, reset the needles was it.
The engine sounded good on the ground but as soon as it was airborn the rich blubbering no power issues were present.
However the engine did stay running, so i landed and tweeked the high speen just a tad and went back up.
It was still gurgleing and running to rich but had a little more power. But after just a few mins promply died.
So off comes the cowl for a flight it dies right on target.
I do know that sometimes a well baffeled cowl with louvers and such is better than no cowl.
So im going to try that next if that dosent work im through messing with it.
theres to many smaller engines out there to be fighting this one or both i should say.
I was asked my set up
20x6 Wood Falcon prop
32:1 Still Ultra oil
Great planes Factor aircraft.
87 pump gas.

I'm still not sure what's going on with your engine.
Was this engine modified or taken part since new?
Do you have another good ignition around or a friend's that you can test on your engine? This will rule out the ignition.
Next, inspect the tank and lines for leaks or if the clunk is moving like it's supposed to.
Where is the tank in relation to the carb? If it's higher it can be a problem with flooding even though there's a pump in the carb. If it's lower it can starve the carb and if it has long lines too it can be harder for the carb to pump fuel.
Don't change out the ring until you sort out the engine. That's just going to add to the confusion.


Lastly, just my preference, change to 92 octane NonE10 gas. It's designed for the compression ratio this engine has and it has a higher boiling point since there's no alcohol.
Try the Xoar prop sometime. I'm using 18x8 or 18x10 and the 35's like it's shape.
Checking the reed block and decking each side and hand setting the reeds is a great tweak for these engines, won't hurt.

Sometimes these engines come with a not so good carburetor that will display those symptoms, mine so far has been good since day one, three gallons through it by now.

Please keep us posted of your solutions.

Hi everyone
The ignition I have not tried yet, but for two engines to exhibit the exact same thing I really have my doubts.
Ok the fuel tank is level with the carb and its pulling gas a whopping 4-5 inches, These carbs can pull fuel straight up for 3 feet, I have yet to see the tank placement on a gas engine create an issues, but there is always the first time.
The older DLE engines said what the CR was on the box and unless they changed it, it was a grand 7.5-1 which even 85 octane is pushing it.
I'm going to dam the cowling and see if that will pull some of the extra heat out of it, other than that there isn't much more I can do.
When the engine is tuned to run correctly it gets to hot and goes away within a very few mins run time.
And the answer is no neither engine has been apart. yet LOL. J/K I will either fix or replace them with something that will run.
Oh almost forgot the prop size a 35 CC engine should be able to swing a 20x6 prop with its eyes closed, My 30 can swing a 19x6-8 easy. If I have to drop to and 18x8 prop then this isn't the engine for me.
I have another 36 engine that will eat a 20x6 but that's another thread.
The instruction manuals say a 20x6 is right in there for the recommended props,

Been looking around a little bit and this post prompted me to join so I could lend a hand. I own a dle35Ra as well as a friend. Mine has 4 gallons or so through it and my friends has 3/4 throught it and his is yet to be maidened.

I broke in my engine on test stand as well my friends with 30:1 Maxima Castor 927 blended castor/synthetic racing oil from the dirtbike shop. First thing I did was throw away dle spark plug and install an ngk cm6 and ive found from both engines that .020 is the happy spark gap.

The manual stated 2 hrs at 4400rpm break in with 30:1. That tells me compression is low from the start and it needs a good break in to be reliable so why would I want to fly an unreliable engine till its right.

I went with 15 to 20 minute runs tuned burbling rich and spitting lots of black gunk out of exhaust. I would run about 3500 to 4k rpm for 2 or 3 minutes, clear it out with a 2 or 3 second gradual open full throttle pull then back to 3500/4000 then idle down to around 2k for a minute, then back up to 3500/4k range and repeat. After first 15 or 20 minutes the engine has changed for better already. Let cool to ambient temp with a fan blowing on engine to speed up the wait time.

Start up and do it all over again but the second run will need a little leaning and subsequent runs after will need little needle tweaks too as the extra gas/oil becomes less needed as ring is sealing.

Both engines run amazing broken in this way and after break in I switch to 32:1 redline synthetic. Lots of black gunk will come out the first tank of redline so the test stand is a good idea for that. My plane was covered so we did that to my buddies to clean internally the leftover castor goo before taking off test stand.

Mine will spin a vess 20A (20x8ish) at 7700 to 7800 on ground and the Vess 19A (19x8ish) at 8100 on ground with one field about 5200 ft asl and the other field about 3600ft asl with a minor needle change between elevations. The yet to be maidened one will spin the 19A 7800/7900 rpms as its still breaking in. My max performance didnt come till about an hour in the air afer the test stand but its been reliable and a total powerhouse from first flight.

LASTLY and VERY important.
I run fiji bottle 3 line fuel tanks from wrongwayrc.com. fill line, vent line and ceramic filter clunk line strait to carb. No inline filters or tees with fill lines on feed line to introduce air leaks or trapped bubbles.

The ceramic filter clunk or walbro felt clunk is crucial from what ive seen on test stand runs. Mine went flawless on test stand with my fiji tank with ceramic filter clunk, my buddies we had problems with. His fiji tank came from a different supplier and cost double but had strait through old style glow type clunks and at 3x4 tank at certain rpms the fuel would froth and it would suck the frothy bubbled fuel up the line and engine would start going lean from air pockets. My ceramic clunk in the prebuilt tank from wrongway will bleead my tank completely dry before you get air and its not a bubble its a completely dry line when it runs out of gas.
My sukhoi went down from a stabilizer failure so my engine (ran on stand after crash and good to go) is now in a factor 30cc as well that is yet to be maidened and the new broken in engine is going in factor as well. If we start having problems with them in the factors then its a cooling issue in the factor cowl and thatll be addressed and I'll report ba​​ck.

​​I suspect half your problems are low ring seal from being new engines and the other half is fuel froth if you used stock tank in the factor as I noticed the strait through clunks that came with mine.

I did have one day that it ran like crap, needles wouldnt change anything, ended up being spark plug boot. Took off boot took circlip off, over bent circlip for tighter boot to spark plug grab reinstalled perfect. Took circlip off after, used a small automotive worm drive hose clamp installed loose around boot shove boot on till seated, then tighten hose clamp to literall lock the boot on. Works great.
I hope something in the above book i mean post help and if anything is vague feel free to ask.

Mike

Edit. How much did you cut open the cowl on the factor?

Hi Mike
i have never been to fond of bench breaking in a gas engine, because of the extra heat they develope over a glow. Gas versis alky ya know
Im going to try a smaler prop and put and air dam on the cowling.
the tanks both are stock with wire ties around every conection,the clunk clears the back of the tank good and has good all around movement.
i really have not had the time to mess with it since i returned from the last flyin i went to.
maybe ill get to it some time this next week
yes all DLE engines have poor compression out of the box the hard rings they use take a long time to fully seat in, i have seen 4-5gal of gas ran thru them before and still not be 100% seated
.i have numerious gas engines and yet had one act like this one is, but i will get it one way or another.
Thanks for the help guys its not going on deaf ears honest.

Hi All
I did the mods I said I was going to do, the smaller prop and the air dam on the bottom of the cowl lip plus reset the carb and had plans to fly it today, but the good old Idaho wind changed my mind.
I did however run the engine for around 15 mins varying the throttle through out the full range and I could not make it get hotter than normal.
I know static running is not the same as flying, but it should give some sort of an idea of what's going to happen.
Anyway until I can stick it back up I won't know if what I did helped or not.

Hi Guys
I'm sorry for not getting back here sooner, but its been busy here with piston making and flyins and trying to get a little flying in myself.
Here is what I found out the 19x6 did help as to weather the air dam did is yet to be seen.
I finally broke down and pulled the jug off and did some measuring and come up with a whopping .006 clearance between the piston and the bore. That told me a heck of a lot about what the engine was doing and why.
So I made myself a new piston with just .002 clearance and moved things just a tad to up the compression a little.
The engine now tunes correctly lost the lower end gargle and screams top end, this is what I expected from the box but didn't get. So mine ran so well and my sons was doing the same exact thing so I made him a piston while I was at it.
managed to up his comp even more than mine. Now I still need to tack mine ,but his is swinging a 20x6 Falcon prop at 7860 to 7910, not to shabby in my book and all of the lower gargles are gone and it tunes right.
Were now using redline oil and none alky gas .But we have not ran it as of yet, our previous setup was still ultra 85 % pump gas 20x6 Falcon prop and a good tune maybe just a tad rich but not very much.
I'm not sure what the deal was I have used several DLE cylinders and pistons when making engines and I have never ran across any before with that issue. I even got several comments on how well the engine preformed and sounded.
So we maybe got a run of pistons that was just a little to loose. Oh I did replace the ring also with a Bowman or Bjorn.
So guys that's what I come up with and of course I know that not just everyone can make themselves a new piston. But I am very happy with the engines now I couldn't ask for a nicer little engine, oh I almost forgot the heating issues in both engines went away.
Richard
AKA Cyberwolf.