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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › General Questions of OSGT15 Mark 2
04-02-2020 04:34 AM  56 days ago
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rrApprentice

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General Questions of OSGT15 Mark 2
Could someone give me some general tips. I might want to consider this in my new RAVE ENV 90 build. Do I need to change fuel tank/ plumbing , gear ratios or are these just direct replacement of say an OS 91 ? Also do they run on unleaded fuel of 25:1 like a weeder? Thanks
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04-02-2020 05:17 PM  56 days ago
ticedoff8

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Morgan Hill, CA. USA

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There are a few versions of the GT15. If you are headed in this direction, get the GT15HZ-II (not the older versions).

In general, the GT15HZ-II (or the older GT15HZ) puts out about the same power as a well tuned, modern OS 55HZ-R or YS 60SR.
If there were a OS 61 still on the market, it would be closer to those.

The GT15HZ works well in 550 / 600 heli with modifications - not so well in a 700 size. Gasser conversions for 700 size would typically use a 30cc motor (the GT15HZ is 15cc). If you plug a GT15HZ-II into a 700, the engine will be running at 100% throughout the flight and still acting like an under-powered 700.

Gas Powered Heli has mods and upgrades that are proven to help with the reliability, cooling and adds a little power.

The GT15HZ-II has some changes that have fixed a few problems from all the previous versions of the GT15.
A newer head for better cooling, changed back to the Walbro carb and changed to a crankshaft with a more standard threaded "snout" for mounting a more standard flywheel / fan / clutch.
The changes help with reliability, but they don't really add power.

OS recommends the 50:1 (3%) oil to gas but for long life you need to get closer to 10% oil (12 oz oil to 1 gal gas = 10:1).
And, the thinner the oil the better.
Red Line 2T or the Morgan fuel that is used in their Cool Power is recommended.

For the Rave 90 (or any nitro powered heli being converted to gasoline) - you will need to change all the fuel lines to fuel line tubing that is meant for gasoline. That includes the bung, the clunk and the tube inside the tank.
The stuff supplied with the kit will melt when you run gasoline through it.

I'd start here: https://www.helifreak.com/showthread.php?t=853987
And, Carey from GPH has this OS GT15HZ-II guide that may be helpful:https://drive.google.com/open?id=19...qkO3Sq16dydTRC5
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04-02-2020 06:23 PM  56 days ago
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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Very good explanation.

You must consider some warning on electronic due to...

... VIBRATIONS...

Take care of:

1.FBL controller reinstalation.
2.Throttle servo.
3.Threadlock everywhere.
4.New liner or new clutch bell on clutch system.
5.Walbro's needles adjustment are quite sentitives on this OS15HZ.
6.Electromagnetic interference.

/
Saludos cordiales,
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04-03-2020 07:26 PM  55 days ago
ticedoff8

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Oh... one more thing:
Also do they run on unleaded fuel of 25:1 like a weeder?
You cannot run any of the 2-stroke motors on straight gasoline. They will all need a fuel / oil pre-mix.
And some will use the Colemen lantern (aka: white gas) fuel as a base instead of unleaded pump gasoline.
It still needs to have oil mixed in, but some say it smells better that pump gasoline.
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Believe 1/2 of what you see and none of what you hear.
Fake News will be the downfall of our Republic!
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04-04-2020 12:36 AM  55 days ago
Dyehard

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Cedar Bluff, Va.

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I've switched over to Crown white gas with 28% oil. It does smell much better, close to what lighter fluid used to smell like and not very strong at all. Crown is available at Walmart and is $4 cheaper per gallon than Coleman. My JR 260Z/230Z is running at least as smooth, if not more smoothly, on the white gas than it did on a 28:1 gasoline/oil mix.Allen Dye
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04-18-2020 02:39 AM  40 days ago
Rojoalfa

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We all appreciate you may post some pics...

A glow to gasser conversion is a complete different situation.

Even, your starter motor/battery pack need to be consider for an upgrade.

Running Temperature... An issue you must consider.
Check for enhanced fan... Metal.

/
Saludos cordiales,
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04-26-2020 12:29 AM  33 days ago
RM3

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Killeen, Texas - USA

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The OS 15gt...

Is to be considered an eccentrics engine... and for expert tuners.

This engine is not recommended for anyone that is not meticulous about tuning and maintenance nor one that prefers to fly any harder than light sport. In addition the engine can easily get overheated so any temperature monitoring system is highly recommended.

My personal opinion is that this is one engine your garden variety helicopter flyer should avoid
showing a preference will only get you into trouble, 90% of everything is crap...
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04-26-2020 01:15 AM  33 days ago
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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It is hard to say but that is correct.

Walbro carb is too big so needle adjustment is happen to be very difficult. One "click" is nothing but two is a lot!

Most of the time, motor is running like burning no matter what you do... 100-130 C...

If you are lucky, you can have 60 flights with this motor... With several overheating in between... No more than that.

/
Saludos cordiales,
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