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HelicopterEngines Plugs Mufflers Fuel › Ys 91 st4 not putting out enough power
08-08-2007 12:39 AM  10 years agoPost 1
mattrcpilot

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Door, MIchigan

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I'm running a Ys 91 st4 with a hatori sb16 and a ratio of 8.45:1 on my raptor 90. I can't seem to get enough power out of the motor. Everything is brand new and the motor only has about 4 gallons through it. I ran it rich as hell for break-in but when I started leaning it out, it doesn't seem to pull that much harder. I lean it out until I hear it crackling, then I land and touch the crank case, and OUCH!! that's hot!! So then I turn the high speed out a little bit, fly again and this time when I touch it it's only slightly warm, but once again, not a whole lot of power. I know my setup is good, I'm only running +/- 10.5 degrees pitch and my headspeed (when I can keep it there) is around 1850 rpm. I really notice the lack of power when I try to do consecutive flips or ticktocks. I tried the 8.27:1 ratio and as expected that was even worse. Can anyone help me? What are the best needle settings for this engine? Is it possible that I got a bad one? and finally, How much power should I expect from this motor. When I watch competition videos they seem to have endless power. And they are (supposivly) runnig the same engine and pipe combo as me. Do I need to dump another heap of money in my motor to get it to perform like theirs? Any help would be greatly appreciated.

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08-08-2007 12:50 AM  10 years agoPost 2
airdodger

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Johnston USA

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Do a search about engine break-in and see if you find anything useful. My opinion is that you do the engine no good running rich, the ring does not seal correctly because the engine never gets to operating temperature. Ring seating happens very quickly and you only get one chance to do it correct. That said how much pitch are you really using? Don't forget the fliers in the vids usually have very good collective management.

Chris

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08-08-2007 01:46 AM  10 years agoPost 3
mattrcpilot

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Door, MIchigan

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I tend to use full pitch quite a bit especially when I do a climbout or prepare for a flip. But When I do a ticktock, It doesnt' seem to matter how much or how little pitch I use, my headspeed just goes away, almost to the point that it's difficult to recover from. Like I said, I'd really like to know what people are running in terms of needle settings. I'm usually very good at tuning engines (I'm a mechanic by trade), but I also know that if you feed it enough fuel in the low to middle settings, It will bleed over into the high setting. The other thing that I should mention is that when I do a flip and stop at mid-stick, it takes a while for the rpms to come back. Is this cause the head is really being loaded down or is it an engine problem?

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08-08-2007 01:53 AM  10 years agoPost 4
DS 8717

rrProfessor

Here wishing i was​somewhere else

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The idle needle will effect up to 25% barrel opening,after that it does nothing and is closed off in the barrel,it has no effect on hover.The long midrange needle works from 25% barrel opening to full throttle,so it has an effect on the wide open mixture. The short high speed needle is only effective from 75% barrel opening to full open,it has no effect on hover or midrange.The long needle is the only one that effects hover.DOUG

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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08-08-2007 02:18 AM  10 years agoPost 5
jsenicka

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Eagle River, WI

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going from cold/no power to hot/cackling in a few clicks sounds like detonation to me. I added an additional .008 shim in my ST4 for 30% fuel, and it makes gobs of power.

Jim Senicka
Team Manager, GrandRC Flight Team

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08-08-2007 02:35 AM  10 years agoPost 6
airdodger

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Johnston USA

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You did not say what percentage of nitro you are using?

Chris

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08-08-2007 11:46 AM  10 years agoPost 7
DS 8717

rrProfessor

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Part of the problem is the helicopter,they aren't the lightest 90 around,and they are kind of slow on the cyclic,also it could very well be the blades you are using.Vblades tend to be boggy and reqire good management. I use to fly them untill i tried some Radix blades,big difference.I even went from 690 Vblades to 710 Radix and it didnt bog like the v"s.

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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08-08-2007 11:57 AM  10 years agoPost 8
colsy

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Cambridge, UK

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going from cold/no power to hot/cackling in a few clicks sounds like detonation to me. I added an additional .008 shim in my ST4 for 30% fuel, and it makes gobs of power.
That's interesting, Tell me 'Jim', where do you get these shims and are there shims already installed in the Motor from new.

My YS has the same 2 'click' difference from good power (but Hot), to Warm and 'Gutless'

I'm running the ST4/SB16 on CY30 @ 8.27 with 690 v's IN MY 90SE, and its almost 'gutless' compared to my AVANT with SZH-PS/SB18.

I wonder if the shim's may help mine.

Colin.

Only Quote From Experience.

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08-08-2007 12:03 PM  10 years agoPost 9
Jafa

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Sydney, Australia

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It should work fine out of the box

Just make sure you have correctly identified the needles
The longer one is the mid range

2 click from cold to too hot would make me strip the carb down
(suspect blockage and crud is in the carb)

The YS does run pretty cool

What is your throttle curve?

Check that your one way is not slipping

Check that your clutch is not slipping

(Hold the rotor head while SLOWLY and CAREFULLY increasing the collective in normal mode, if you can get to half stick and it's still easy to hold then something is slipping - BUT BE CAREFULL doing this)


Protos | Logo 400 & 500 | Sceadu Evo | Freya Evo | Trex600N | Avant FX

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08-08-2007 01:26 PM  10 years agoPost 10
jsenicka

rrProfessor

Eagle River, WI

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Colsy,
was running same config and fuel.
Added a second head gasket [YSE4780 Head Gasket 91H]
from Heliproz.

It gave me a much wider needle range, and better power on top end before any cackling. The engine comes with one stock head gasket, about .008. I simply added another.

Jim Senicka
Team Manager, GrandRC Flight Team

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08-08-2007 01:40 PM  10 years agoPost 11
DS 8717

rrProfessor

Here wishing i was​somewhere else

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Colsy,try some different blades. My vibe was like that with Vbalades untill i changed them,it is like a totaly differnt heli.For those in the US ricks has shims in .002 and .004 for the Ys 80 and 91 ST.DOUG

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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08-08-2007 01:56 PM  10 years agoPost 12
colsy

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Cambridge, UK

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Thanks for the help.

Yes to blades, i have swapped the 690 Radix from the Avant, to the 90SE. As the AVANT will handle the V's better anyhow.

So next flying session will tell me if the blades help. If not ill pull the carb.

Heli climbs fine in a straight ascent both upright and inverted, with +/- 11 pitch, and holds stationary flips without loading up.

But trying to sustain Elevator or Aileron Tic-Toc's just loads up with minimal collective.

Does anyone know if the OS shims are compatible ??

Thanks Again.

Col.

Only Quote From Experience.

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08-08-2007 02:05 PM  10 years agoPost 13
DS 8717

rrProfessor

Here wishing i was​somewhere else

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I had some 690 Vblades on my vibe and it was slugish even with 11 degress pitch,now with 710 Radix SB blades i am using 13 degrees and it pulls better.I have 1 stock .008 shim and 1 .004 shim in my 91ST with 30% magnum fuel.By the way the raptor head has a pretty wide spacing on the blde grips so the blade disc is larger than most heli's and is wider than the avant head i believe.DOUG

YOU ONLY LIVE ONCE..IF YOU LIVE IT RIGHT THATS ALL YOU NEED

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08-09-2007 12:46 AM  10 years agoPost 14
mattrcpilot

rrNovice

Door, MIchigan

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I'm running thunder tiger 710's with no slipping anywhere, (I checked) I've tried several fuels all in 30%. Wildcat CY, coolpower,byron, coopers special blend. None have any more power over the other that I can tell. I will try the extra shim. I"m taking the carb off tonight and going through it thoroghly. Transitions from idle to mid to high are smooth though, so I don't think anything is too wrong with the carb.

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