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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Good 90 size engine.
02-27-2016 07:58 AM  32 months agoPost 1
PaulBowen

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Victoria, Australia.

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Just wondering what peoples opinions are on the smoothest and easyest tuning 90 size engines available.

The helicopter is a Hirobo D3v2. Gear ratio 8.77/1 sport flying, 1700rpm+-.

I have an OS105HZ-R and am not completely happy with the experience.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-27-2016 11:11 AM  32 months agoPost 2
nickwap

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Berwick-upon-Tweed, Northumberland, England

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Personally I have had great experience with the YS91's and Hatori Pipes,
need to have a leak free fuel system but great engines.

nick

"Give me another one, this one's broke!"

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02-27-2016 11:27 AM  32 months agoPost 3
PaulBowen

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Victoria, Australia.

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I quite like the look of the new YS-96SRX Tareq. Not sure how easy the tuning will be. I've never owned a YS before but they seem very popular. I prefer to run 15-20% nitro as well because fuel is very expensive in Australia.

The other option available to me is an OS Speed 91HZ-R 3C. Not sure what they are like compared to the 105HZ-R

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-27-2016 02:29 PM  32 months agoPost 4
Dawiev

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Middle East

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What makes you unhappy with the OS 105? What do you want the new engine to provide?

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02-27-2016 08:28 PM  32 months agoPost 5
PaulBowen

rrKey Veteran

Victoria, Australia.

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The 105 idles like a jack hammer and isn't particularly better in flight. My engine has different mixture settings on every flight. It seems to have very strange tuning characteristics. It is also the thirstiest engine I've ever seen.

My 105 has 10 hours on the clock now and has never required removal from the helicopter. It worries me as this seems quite a long time for the 105 from much that I have read.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-28-2016 03:29 AM  32 months agoPost 6
Dawiev

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Middle East

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Hi, I would suggest you check the internals - at least remove the pipe and check through the exhaust port what the insides and the side of the piston looks like.

The "jack hammer" noise is indicative of rear bearing gone ? It also seems these engines are prone to breaking the piston ring locator pin.

At the very least, it must idle properly. If it doesn't, there is something wrong and having it in hand should tell you quick enough. You'll feel and hear the rear bearing, if it is shot, easily with the backplate off and spinning it by hand.

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02-28-2016 03:43 AM  32 months agoPost 7
PaulBowen

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Victoria, Australia.

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It idles perfectly for extended periods of time. Inside it looks like it hasn't run. The problem is the fact that it is not a nicely balanced engine particularly at lower revs, especially idle. And yes I have installed the flywheel and clutch as true as possible.

My OS 32SX-H runs much much smoother, and it's worth less than half price of a 105. That's annoying.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-28-2016 07:30 AM  32 months agoPost 8
human213

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malibu

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YS
I have a new Tareq .91 for sale if interested.

Not everything that can be counted counts, and not everything that counts can be counted.

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02-28-2016 03:08 PM  32 months agoPost 9
don s

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Chesapeake, VA

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Is your crank bent?

E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.

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02-28-2016 04:22 PM  32 months agoPost 10
Rodney Kirstine

rrApprentice

Caldwell, ID - USA

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Paul, my 105 runs very smoothly. The only time mine has idled roughly was when the pin in the piston ring groove sheared and the ring rotated. OS recently made a change and replaced the roll pin with a solid pin. You might also have the high speed needle valve seat with the over-sized orifice. An easy way to check is to remove the high speed needle valve and, if you can in insert a 1.5mm Allen wrench into the orifice, it's too large. Mine was impossible to tune prior to getting the replacement needle valve seat.

So, to answer the OP, I really like my 105 now that the two issues I had with it have been addressed.

I do have a YS 91 SRX, but I haven't run it enough to really give a good opinion.

Rodney
Team Synergy Field Rep, Rail Blades

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02-28-2016 06:30 PM  32 months agoPost 11
PaulBowen

rrKey Veteran

Victoria, Australia.

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Would anyone know the part number for the improved needle valve seat?

I think I should give it a go.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-29-2016 01:51 PM  32 months agoPost 12
utahbob

rrVeteran

St. George Utah

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my fav
OS 91 Hzr..stone reliable!

I do a great decending funnel!

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02-29-2016 08:10 PM  32 months agoPost 13
Rodney Kirstine

rrApprentice

Caldwell, ID - USA

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Would anyone know the part number for the improved needle valve seat?
I think I should give it a go.
Did you check yours and find it to be too large? The part number didn't change, same with the new piston. I ordered the piston from RCJapan and the new one I received has the solid pin. I got my needle valve seat from the U.S. distributor of O.S. motors, though.

Rodney
Team Synergy Field Rep, Rail Blades

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02-29-2016 10:17 PM  32 months agoPost 14
PaulBowen

rrKey Veteran

Victoria, Australia.

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I have checked my needle valve assembly and the hole is over sized. I may purchase a new piston also as a preventative measure.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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02-29-2016 10:26 PM  32 months agoPost 15
Rodney Kirstine

rrApprentice

Caldwell, ID - USA

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The needle valve seat replacement makes a huge difference! I was about ready to throw my 105 in the trash and now it's very easy to tune.

Rodney
Team Synergy Field Rep, Rail Blades

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03-01-2016 12:34 AM  32 months agoPost 16
PaulBowen

rrKey Veteran

Victoria, Australia.

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Thanks Rodney, I think that's what I need to do.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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03-01-2016 04:31 AM  32 months agoPost 17
PaulBowen

rrKey Veteran

Victoria, Australia.

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Removed muffler. This is after 10 hours of running. There is a slight rub/scuff mark about 4-5mm wide on the front left hand liner surface. I'm not sure where the ring pin is located.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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03-01-2016 03:01 PM  32 months agoPost 18
Rodney Kirstine

rrApprentice

Caldwell, ID - USA

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The ring pin is at about 11 o'clock, looking at it from the top with the exhaust port being 3 o'clock.

Rodney
Team Synergy Field Rep, Rail Blades

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03-01-2016 06:23 PM  32 months agoPost 19
PaulBowen

rrKey Veteran

Victoria, Australia.

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There is slight marking in that location. Not really sure if it is normal wear or not. It is quite hard to see.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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03-03-2016 02:42 AM  31 months agoPost 20
Felino

rrApprentice

Mexico city

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Check out the gear ratio.
8.77 is not useful for the 105HZ.
Try something like 8.0 8.18 or 8.27
I think the original D3v2 ratio is 8.27
Go for it.

Happy autos!!

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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Good 90 size engine.
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