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HelicopterEngines Plugs Mufflers Fuel › Engine will not start
06-22-2014 02:35 PM  3 years agoPost 1
rudyy

rrElite Veteran

E. Amherst, NY

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I have a YS91 SR 3DS engine that will not start after having a lean run that burns a plug.

I have checked and performed the following:

1) lots of pressure from the pressure valve as when I release the pressure, I can hear the hissing sound
2) lots of compression when I turn the crankshaft
3) replacing two new glow plugs with no luck
4) fuel can get into the engine as there are lots of fuel coming out of the engine if I crank it with the plug taken away

I have partially dismantled the engine and clean the carb and all needle sockets.

I have noticed that the cylinder liner was scorched a bit, but I would have thought this would only weaken the compression.

After everything I have done, the engine just will not start.

Any help would appreciate.

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06-22-2014 03:01 PM  3 years agoPost 2
REGULATER

rrApprentice

Bakersfeild, CA

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I would say you will need a new piston ring and sleeve. if you had a lean run I can almost guarantee it, I have had this problem more than once. Sorry for the bad news. Call YS and Richard will take care of you

Mark

Mark Lattimore
Miniature Aircraft USA
YS Engines
Cool Power Fuel
MKS Servos

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06-22-2014 03:10 PM  3 years agoPost 3
rudyy

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E. Amherst, NY

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This is what I am thinking too. But what I do not understand is that it still has lots of compression when I manually turn the crankshaft. I would have thought it should still be able to start but with not enough power. Yet, it just has no sign of starting up at all.

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06-22-2014 03:41 PM  3 years agoPost 4
Rob43

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Midland, MI USA

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Check that your ignition source is indeed glowing the new plug you installed. I have a Pushglo, and it was giving me the tone like it was working properly. I cranked and cranked on the engine with no start. I removed the plug, checked it with my glowstick, and it was perfect. I put it back in, and put the glow stick on it, and it fired the first crank.

You mentioned seeing "scorching" of the liner. Have you examined the piston crown? The seating of the ring? The ring should be black with no scoring. Scoring damage seems to happen most often aligned with the exhaust port. If there had been any detonation in the past, it could have caused damage. It could still be hard to roll over like it has good compression, but still not ignite, even with good glow.

Rob

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06-22-2014 03:46 PM  3 years agoPost 5
rudyy

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E. Amherst, NY

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I do not use on board glow. The ignition source is good as it can start another nitro easily.

So, I guess the conclusion is I will need a new ring and a new liner.

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06-22-2014 04:40 PM  3 years agoPost 6
Glenn Goodlett

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California

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I've done exactly the same thing. Once they cross some unknown threshold, they just won't run. Sorry, but I think Mark is correct.

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06-22-2014 08:17 PM  3 years agoPost 7
GREYEAGLE

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Flat Land's

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Sound's silly : But if it has all the good sign's you are positive about & mentioned :

Fish a dental mirror up in their and with a Mag lite examine the carb throat opening in relation to your throttle stick position.

Take a peek / Silly --- YES :::: but ya never know

greyeagle

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06-22-2014 09:25 PM  3 years agoPost 8
airdodger

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Johnston USA

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Check the rear bearing, if it has too much drag the engine won't start at idle.. You only need fuel compression and ignition source, it's not magic. A quick seize can place too much drag also.. Place some fuel down the carb and see if it starts. Just because the plug is new does not mean it is good.

Chris

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06-22-2014 11:03 PM  3 years agoPost 9
dkshema

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Cedar Rapids, IA

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What caused the lean run?

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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06-22-2014 11:17 PM  3 years agoPost 10
rudyy

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E. Amherst, NY

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What caused the lean run?
Pipe O-rings wearing out.

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06-23-2014 12:28 AM  3 years agoPost 11
jason46

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MI

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Just a thought
Was the liner removed when you partially dismantled it, curious if it was misaligned on assembly.

We made up some rules can we have your moneys now.

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06-23-2014 01:22 AM  3 years agoPost 12
rudyy

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E. Amherst, NY

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No, I did not take the liner out. I only dismantle the carb and the throttle body.

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06-23-2014 07:46 AM  3 years agoPost 13
Brendan78

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NSW Australia

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Hi Rudyy, what fuel/plugs are you using? I had an issue (mentioned above) where the plug was glowing, but not enough from the ignition source and the engine wouldn't fire, and as the fuel came in, the plug got too wet due to the weak glow(mine wasn't a lean run, but engine just wouldn't fire). Was especially prevalent with a cold plug (like the enya 5). I know you have mentioned it starts other nitros, but are you using an OS8 and 30% nitro? Just thought I'd check. Have you taken the head off and looked at the top of the piston and the head as well? It may very we'll be that the liner/ring is finished, but worth exploring the above first. Is the plug wet when you take it out? Are you getting hydro lock at all?

Raptor 90 G4 / YS120SRX / VBar Silverline / Futaba / Rotor Rage / Edge

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06-23-2014 12:45 PM  3 years agoPost 14
rudyy

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E. Amherst, NY

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Hi Brenda, I am using 30% nitro wildcat with OS#8 plug.

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06-30-2014 02:05 PM  3 years agoPost 15
rudyy

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E. Amherst, NY

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Here is the update. I replace the cylinder liner, piston and ring and the engine is back to normal.

Thanks for everyone's help.

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06-30-2014 09:03 PM  3 years agoPost 16
airdodger

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Johnston USA

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Should have done the rear bearing at the same time. The bearing probably suffered from lack of lubrication also. Keep a close eye on it, if it makes noise at idle that is a clue. Thanks for update nice to know.

Chris

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06-30-2014 10:09 PM  3 years agoPost 17
Rob43

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Midland, MI USA

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Nice to know that sometimes, just dropping the cash solves the problem.

Rob

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06-30-2014 11:56 PM  3 years agoPost 18
REGULATER

rrApprentice

Bakersfeild, CA

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Way to go Rudy I'm very happy to here everything is working good. Now go burn some Nitro.

Mark Lattimore
Miniature Aircraft USA
YS Engines
Cool Power Fuel
MKS Servos

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