scoobiemario

My Feedback: (8)

Hello, I'm fairly new to gas engines in airplanes, so maybe someone can help me out here.
I got MLD35 with Walbro carb (WT202) in GeeBee.
It flew fine for 7 flights. Easy to start. With exception of two deadsticks. Engine died mid throttle. I Adjusted throttle curve and it was much better.
Than I had some problems starting it. It would start, revv up a little and die. Took carb off, cleaned it, and it worked for 3 flights.
Now I can not start it at all.
Choke on, little throttle, ign on, flip 5-6 times,
pops, choke off. And it won't start. So Choke on again, flip flip flip. it will pop or even revv up like it want's to run for a second. It dies. I keep flipping it, and it floods. remove plug, clear gas, plug back, flip, flip. And it want's to start, but it dies quickly.

So I checked plug/replaced it. Spark is nice. Tried different ign battery. When I rotate prop slowly I can even hear spark inside of cylinder.
Hi/Low needles are in same place they were before. I use same gas as on DA50, which runs great.

I took carb off, checked it, checked reed valve. Replaced gaskets between reed valve and engine/carb. There was never much crap in carb. I have fuel filter on the plane and on gas can.
Still same, can't start it.

I ordered carb rebuild kit. I'll try that. If not, I'm thinking to get carb from DLE35 RA. It has same foot print, and it's for same displacement engine. So it should work.

Anyone has any suggestions??
Thanks
Mario

kmeyers

This is what I see first.

You are assuming the first owner had it right because you had 7 good flights?
I say start with data.

Close needles counting the revolutions to closed, write them down.

Go through a normal tuning process. I call this "taking ownership".

What prop are you using?
You adjusted the curve, what about the end points?

ahicks

My Feedback: (2)

If you can hear the spark, in my experience, you have a defective silicone insulator inside the spark plug boot.

Was one of your landings a little less than graceful, that might have allowed the plug boot to drag on the runway surface? Been having trouble with it since? If so, that plug boot is your issue. Replace it and you'll be good to go.

scoobiemario

My Feedback: (8)

Originally needles were at 1.5 low and 2.25 high. I ended up with 1.5 low and 1.75 high, and engine was running better in my and others opinion.

There was no rough landings when I flew it, and engine is completely hidden in cowl, so plug is protected.
ahicks, you don't think I'd hear spark from inside the engine? That's in garage, when I spin it slowly by hand.
Also, when plug was outside of the engine, it had nice strong spark.


Even though I think plug boot is fine, I do not mind to replace it to be safe.

scoobiemario

My Feedback: (8)

Oh, prop is 18x10 Xoar, and end points are adjusted as well, throttle max is actually at about 75%

ahicks

My Feedback: (2)

Plug sparking when installed in boot, may not happen when under compression. That's one of the reasons the bad plug boots are so hard to troubleshoot. The engine's compression can change the resistance just enough to cause it to leak through a defective insulator rather than jump the the plug gap.

If the plug boot didn't hit anything it's likely OK - until you say you can hear the spark. At that point, I have to think something is going on there.

Do you have access to another ignition module?

CK1

My Feedback: (60)

I think Ahicks has very good points and to add to his input I would say that most boots get damaged when removing the cap from the plug . The plane doesn't have to experienced a crash to have damaged to plug boot inside the cap . Too much prying and twisting gives the same result.
Try another ignition ,borrow one from a buddy and see how it goes. Replacement caps are cheap and easy to replace once you verify the issue.

Truckracer

My Feedback: (19)

+3 on the plug cap. Good advice from others on this thread. If you can hear a spark when the plug is in the cylinder, something is wrong.

I'd add to the above, some of the MLD ignitions were less than reliable from day one. When these engines were being sold, the forums were full of complaints about the ignitions. If your engine is not already so equipped, I'd just replace the ignition with an RCexl, RCXP or CH. RC Extreme Power is a good source for a reliable ignition, plug caps, etc.

scoobiemario

My Feedback: (8)

Thank you all for feedback.
It is strange, that engine's compression can cause spark plug misbehaving. I'd like to know more about why it happens.

I do not have another ignition handy.
But I did hear about MLD ignitions failing too. I'm thinking to save time, and frustration, I might just get RCXP ignition. And if then I still can't get it right, I'll look into carb little more.
I'll update this thread when I try again.
Thanks again!

CK1

My Feedback: (60)

Electricity will always follow the path of least resistance. An increase in cylinder pressure will increase the resistance of the spark to jump the gap of the sparkplug. Adding fuel to the air mixture in the cylinder will increase the resistance even more . A crack or hole in the silicone boot will provide a path to ground with less resistance than that of the spark plug in the pressurized cylinder

bcchi

Hicks is right,you are not hearing the spark inside the cyl.Your hearing it in the plug cap.You need a cap and boot kit.
BCCHI

scoobiemario

My Feedback: (8)

Yeah, RCXP ignition is on the way already. I don't trust original ignition with all the failure reports anyways.
I should be able to test it this weekend.

BadAzzMaxx

Mount the new sensor that comes with the ignition, The original sensor on the MLD will not work with the new ignition.

milton

scoobiemario

My Feedback: (8)

Yes. Original sensor has weird connector. Not the servo connector type

scoobiemario

My Feedback: (8)

OK. So ignition arrived yesterday. I installed it and timed it at 28 degree before TDC.
AAANNNDDD>>>>>>>
IT WORKS!
I owe you all a beer! I really appreciate all the input. Nothing can beat combined years of experience!

It started easily and ran good for the most part. (Details later).
I also just got NGK CM6 to replace DLE CM6 that I have. I've heard bad things about DLE plugs.

Now details:
So I have flown it 4 times. Got to land deadstick on first flight though. I was pretty throttle happy, going fast, having fun.
I was going at 30% of throttle straight and level, pulled up a little and advanced throttle to 70-80%. Engine died.
Landed, no damage, and flown 3 more times after that with no problems.
Although, I was little more gentle on the throttle after that.

Did some touch and goes.

From what it sounds like, and what other guys say it was little rich on low end.
On throttle up, and than down RPM's come down to certain point slightly higher than idle, before settling down at idle. After one or two landings, idle came down pretty low and engine died twice.

If someone has some advice, I'll take it gladly.
On the side note, I did get Walbro rebuild kit, and thinking to replace diaphragms.

PS: prop is Xoar 18x10 and revvs up to 7600 RPM.

Thank you all again!!

ahicks

My Feedback: (2)

Glad to hear you have it running, and it sounds like you're close on your tune.

So, if you were "ground" tuning, and it quit or stumbled badly when accelerated hard, what would you do? The same would apply with what it sounds like it's doing in the air. Richen the low speed. Note that richer mixture might lower your idle speed a hair, so no surprise if you need to bump that up slightly as part of the richening move.

The ground tuning is just a start on your final tune. It will very nearly always require some tweaking once airborne.

Last, from a tuning standpoint, rich engines don't quit. It's the lean ones that do that (heat/overheat being the exception).

scoobiemario

My Feedback: (8)

It seems to me like I'm getting signs form two opposite ends of the spectrum. You say it might be little lean. I took the plug out today and replaced it with NGK. One I took out was wet and little oily after only 4 flights. Also there is abit of burble on low throttle fly by's.

I replaced diaphragms and gaskets in carb, and blew the passages. I also polished reed valve contact surfaces (400,600, 1000 sandpaper on glass surface). They were not that great from factory.

i started it today, and ran it little bit. Runs fine, starts easy. can't really tell the difference on the ground in the back yard

So, you said rich engine will not quit? How about at idle speeds? Would it quit when rich?
Thank you

ahicks

My Feedback: (2)

If it's quitting at idle speed on the ground, the idle is likely too low. In the air, too low, but that could be lean as well.

There's an easy way to see who's right. Try both answers.

scoobiemario

My Feedback: (8)

I will try this weekend if weather is good. thank you