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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › OS Hyper 50 problem
01-19-2010 01:00 AM  8 years agoPost 1
jac5304

rrNovice

Mount Juliet, Tn - USA

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hello,
I have a os 50 and the rpm surges up and down when it is leaned out to where it should be. About 1 1/4 turn. It sounds like it is sucking air somewhere so I installed now o-rings and it still surges. If I rich-en it a lot it does not surge. About 2 turns. has anyone had this same problem? Could this be caused by a bad rear bearing? How to you tell if the bearing is bad? Any help will be appreciated. I'm about ready to trash it and buy a new YS 50. This motor came on a used heli I bought here on RR.

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01-19-2010 01:28 AM  8 years agoPost 2
Against Gravity

rrVeteran

Pottstown PA

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Bearings
Check your bearings, If they are bad it can run like that.
You have to disasemble the engine. When you get the piston out rotate the crank and see if it is smooth.

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01-19-2010 01:38 AM  8 years agoPost 3
jac5304

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Mount Juliet, Tn - USA

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Thanks for the reply. Are there any disassembly instructions on RR I can use?

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01-19-2010 01:51 AM  8 years agoPost 4
Chook

rrApprentice

Esperance Western Australia

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01-19-2010 01:58 AM  8 years agoPost 5
jac5304

rrNovice

Mount Juliet, Tn - USA

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Thanks chook, looks like some good info. I'll try it.

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01-19-2010 02:25 AM  8 years agoPost 6
Chook

rrApprentice

Esperance Western Australia

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Not a problem. You reminded me about my hyper. I just checked my log book and it has had 72 tanks, so I'm off to overhaul it once again.

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01-19-2010 06:26 PM  8 years agoPost 7
BarracudaHockey

rrMaster

Jacksonville FL

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What fuel are you using? 1 1/4 turns is only a guide line. There's a lot of places you could be sucking air, especially check the clunk line and change the plug before you go tearing into the motor.

Andy
AMA 77227
http://www.jaxrc.com

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01-20-2010 02:12 AM  8 years agoPost 8
Dirthead

rrApprentice

Thornton Co.

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Lots of places, head, backplate, carb for starters.

Keep ur head out the dirt only in the grass

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01-20-2010 02:18 AM  8 years agoPost 9
jac5304

rrNovice

Mount Juliet, Tn - USA

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Barracuda, I use 30% and I changed all the fuel lines. I even bypassed the header tank and it still surged. I will just surge at a steady trottle, such as hovering. When I get on the gas it seemed okay.
Well, I tore it down today and the cylinder sleeve and piston ring are galled or scored. It's just two small places about 1/8" wide but I think it's enough to make it not run right. Not sure if this would make it surge up and down though. The bearings don't seem to be notchy at all but the rear one is noisy. I was checking on the cost of replacement parts and it looks like a new engine is only going to cost about $70 more. Is it worth rebuilding? I was thinking about getting a ys 50. There's a lot of people on RR that say it's a better engine. Thanks for all the info.

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01-20-2010 03:47 AM  8 years agoPost 10
Twrecks600

rrKey Veteran

Round Rock, Texas

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Just get the 55!! I put one in about 12 gallons ago and it has mega power compared to the 50!!

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01-20-2010 06:08 AM  8 years agoPost 11
Sam2b

rrElite Veteran

Tacoma, WA

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I had the same issue, RPM surging both up and down. Consider replacing your throttle servo, or at least inspecting the governor wires. It may be hard to beleive but I trouble shot everthing and the throttle servo was the culpret. Throttle servos wear out too especially if not stepped down to 5v.

Assuming you didn't troubleshoot everything, did you replace all fuel tubing including the clunkline? Did you tighten the carb screw while pushing down on the carb onto the engine block? Did you gradually tighten the head screws in a star sequence? Does the engine surge during a full tank of fuel?

I'm sorry to say a bad rear bearing will not cause rpm surging symptoms.

_Sam B_

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01-20-2010 11:28 AM  8 years agoPost 12
jac5304

rrNovice

Mount Juliet, Tn - USA

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Thanks for the info Sam,
I did not think of the throttle servo being bad. I was just checking some hitec servos I had laying around the other day to see if they were good and one of them was jumping around. I will check this out. I did replace all the fuel tubing and the clunk lines. I put a new o-ring on the carb and made sure I pushed it down. Can the scoring in the cylinder and piston ring cause this surging? The engine is torn down now. I'm trying to decide if I should rebuild it or buy a new one. I fly a JR Voyager and I will be getting Trex 600 this weekend. Going use electronics from the voyager.
Thanks for the input.

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01-20-2010 07:37 PM  8 years agoPost 13
Sam2b

rrElite Veteran

Tacoma, WA

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You're welcome, jac5304.
The scoring will not cause engine surging either. If you can catch your fingernail in the score line on the piston, ring, or sleeve then it is time to rebuild for sure. Just remember to use After Run oil while rebuilding so parts are lubed.

Good luck on the new Trex600. It's a good air frame. And good luck with replacing the throttle servo. I look forward to your results!

_Sam B_

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