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HomeAircraftHelicopterMain Discussion › Help what causes engine pulsing
04-07-2015 06:38 PM  3 years agoPost 41
datidun

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N Ireland

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Richard look at my photos again,that has been checked with rule and protractor,end points are 100.100,carb is exactly half open at exactly half stick on my radio,some say the end points should be exactly the same top and bottom others have 10% to 15% difference,thanx for posting the video,mine does that in idle up but not as bad.

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04-09-2015 08:57 PM  3 years agoPost 42
ICUR1-2

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Ottawa, Ontario

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Did you get a chance to try out the 9257 ?

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04-10-2015 03:16 PM  3 years agoPost 43
goof2

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Bristol,CT

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Are you using stock arm on motor? I would shorten servo arms even if your over 100 on end points

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04-10-2015 07:08 PM  3 years agoPost 44
Tyler

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Chicagoland area

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Sometimes a failing one way bearing can cause engine surging on certain mechanics and power system designs.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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04-17-2015 09:48 AM  3 years agoPost 45
datidun

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N Ireland

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New 9257 installed and its still doing it,its must be down to the Governor settings,all new plumbing ,new servo,another sensor,another muffler,new filter,mechanical set up is perfect,these are the settings in the throttle curve
Normal mode 0.40.40 =1800hs
idle up 1 60.60.60 =2000hs
idle up 2 100.100.100 =2100hs
My throttle curve has 7 points, 3 are used low middle and high,the rest are inhibited,any body running a different throttle curve,this is done by the Skookum Wizard word for word.

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04-21-2015 08:38 PM  3 years agoPost 46
datidun

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N Ireland

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Whats the best way to check if the one bearing is is going bad,I was out again tonight tank after tank,this time I had the engine and muffler from my Trex which runs really smooth,it still pulses in the Synergy,thats two new sensors and a new throttle servo,I started the gain from 15% and ended up with 80% and it did not make a single bit of difference,must be a bearing or something effecting the motor,but it only does it in idle up 2050,the kit is only a year old, I just checked I turned the head anti clockwise and held the main gear,nothing is slipping.

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04-22-2015 01:03 AM  3 years agoPost 47
Jason Cummings

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St. Louis

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Could it possibly be a crossover on the needles where the low needle is too rich so the gov adds throttle which puts the motor on the high needle which is i little lean so it lowers throttle and on and on? Also going up or down on the head speed may make a difference too. Let us know how it goes.

Synergy Field Rep

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04-22-2015 08:45 AM  3 years agoPost 48
RotorHead486

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England

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Hi Datidun,

Do you have a picture of your sensor setup? This is something i have had myself with the spektrum backplate sensor and they can be quite picky with the distance they are set from the back plate and will sometimes sense the crank and sometimes they won't giving inconsistent running or pulsing similiar to what you are experiencing.

One Reason For Crashing'Rogue Servo Bent on World Domination'!!
FLP Flight Team

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04-22-2015 09:30 AM  3 years agoPost 49
datidun

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N Ireland

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Ok thanx Rotor head,I set the back plate the same as my Trex 600 which has a washer in between the plastic and back plate itself,that did not work,but checking through the PC the sensor is working,then I removed the washer and the sensor is right up against the back plate quite tight,that does not work either,but the Skookum tells me its working,Idle needle is on the rich side,pinch test is good,starts to rev after 2 second and lasts for 5 sec

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04-23-2015 12:03 PM  3 years agoPost 50
Busher

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Manchester, England

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Remove the bearing, clean it thoroughly then inspect for any wear in the cage or the rollers, if it's good the re lube with thin oil. I've had this on my rappy and it didn't disappear till I cleaned and lubed the owb, it all looked ok but it returned a couple of tanks later. Turns out there is more to the owb and how it works with a driven tail than meets the eye.
The trouble is once the owb starts slipping it dosent stop till the revs decline. I replaced the owb and it was gone, I also converted the heli to constant driven tail, the extra load seemed to help the owb engage and stay engaged.
It's worth a shot to clean it, and I bet your surprised how much crap comes out of it, if only one of the rollers fails to step into the correct space in the bearing cage it will slip.
I think Tyler posted about these bearings maybe 10 years back, who ever it was it was most informative and explained how they work, I'm surprised they even stand up to the abuse we give them .

Good luck
Busher

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04-23-2015 04:19 PM  3 years agoPost 51
datidun

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N Ireland

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I turned the head anti clockwise and held the main gear,there was no slipping,I have another Skookum 540 on there with new tape,just want to see if it makes a difference or if its vibration related,if this does not work then I will have to start stripping things down,if its not the engine,fbl unit,plumbing,sensor,then it must be a bearing or something

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04-23-2015 05:57 PM  3 years agoPost 52
Tyler

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Chicagoland area

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I would bet on the following cause in this order of likelyhood:

1. Bad one way bearing
2. Damaged FBL controller
3. Bad engine rear bearing or needles way off on tune
4. Excessive vibrations due to incomplete rebuild after crash, something is buzzing
5. Worn servo or sensor wire that is shorting out against a frame or metal
6. A bad servo lead connector or bad pin on a servo lead (pin tab broken allowing pin to move inside the plastic housing)

Enjoy things that money can buy IF you don't lose the things money can't buy.

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04-23-2015 07:59 PM  3 years agoPost 53
datidun

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N Ireland

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Nope I cant think any of those,will know tomorrow as I have put on a different Skookum,top and rear bearing are all good,the 2x sensors, muffler and a tuned pipe and both engines were in two other helis two weeks ago all were good,little bit of vibration when starting which is normal as the idle is on the rich side,cant hear or notice anything in the hover.

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04-24-2015 02:54 AM  3 years agoPost 54
Tyler

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Chicagoland area

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What are the top and rear bearings you mention?

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04-24-2015 08:09 AM  3 years agoPost 55
datidun

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N Ireland

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Engine bearings,rear one and top of the crankcase,the small one were the threaded shaft goes through,both have been replaced.

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04-24-2015 12:44 PM  3 years agoPost 56
Tyler

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Chicagoland area

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Thanks for clarifying.

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04-24-2015 10:01 PM  3 years agoPost 57
Tyler

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Chicagoland area

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What is the report? Anxious for news.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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04-25-2015 06:39 PM  3 years agoPost 58
datidun

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N Ireland

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Well I put on another Skookum 540,it came off my old Raptor which works 100%,I dropped the idle up head speed to 2000 from 2050,took off in normal mode 1800 and hovered there for a minute,could tell it was rich in the mid range as there was really plenty of smoke and I could hear it as well,then I changed went into idle up,just hovered for a minute as well at this stage its running fine,then a full high climb out came down into the hover,,then MR pulse is back all the way causing the tail to kick,flick back into normal mode 1800 and its fine,gov gain set at 50%,at that stage I was not even going to bother lowering the gain,it would not make a difference,took out the engine OS 55 hz,took off the head and the gearing and had a good look at the one way bearing carefully,its like new inside,no dirt all the rollers look fine,cleaned it anyway,oiled it up and put it back,this time with a well run Hyper 50,final checks all gears are smooth,clutch bell and starter coupler are all smooth no drag.

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04-25-2015 09:02 PM  3 years agoPost 59
Tyler

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Chicagoland area

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Changing too many things at once. This episode has become a complete basket case.

Looking at a one way bearing may not be good enough.

Hovering and chopping collective is not suitable to tune an engine and set proper needle relationships.

Tuning engine with governor on is not common practice for a reason.

In my opinion, and I believe many long term veterans here would agree with me, you have entered a goose chase and are making too many mistakes.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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04-25-2015 09:06 PM  3 years agoPost 60
Tyler

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Chicagoland area

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Would you mind telling us how you tune an engine, step by step, in great detail?

I bet the engine tuning is off. I'll expound further after carefully reading your engine tuning narrative.

I've written extensively on this in the past and helped many pilots.

Enjoy things that money can buy IF you don't lose the things money can't buy.

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HomeAircraftHelicopterMain Discussion › Help what causes engine pulsing
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