Venturi Insert for SuperTiger G21 35

Stuka Stunt Main Forum · 16 of 16 known posts recovered

klelmore · Nov 18, 2004 10:12 AM

LAST EDITED ON Nov-18-04 AT 03:46 PM (CST)

I have a SuperTiger G21 35 that has the large venturi, which requires pressure for the motor to run. I used it in my brief foray into combat and recall that it *screamed.* I'd like to tone it down a wee bit. Where might I find a replacement venturi so that the motor would run on suction?

Kim Elmore

AMA 56239
"All of weather is divided into three parts: Yes, No and Maybe. The greatest of these is Maybe."

hothandle · Nov 18, 2004 11:40 AM

#1 source

Check with Jim Phillips, he may have a suction venturi.

Hothandle

T.Durrill · Nov 18, 2004 03:01 PM

#2 source

Just a suggestion.............you might try replacing the high compression head with a head from a ST .35 plain bearing stunt (baffled piston model). I have one on one of my G-21 .35's and although I have yet to run it, it noticably lowers the compression and I expect it will make for a milder run. The G-21 .35 is certainly a powerhouse in stock form and is a handful on any sport or stunt type airplane.

T.Durrill

klelmore · Nov 18, 2004 03:45 PM

#3 source

An excellent idea. I'll try that. Yeah, I recall that this thing was pretty impressive. Ball-bearings still feel smooth as silk and it's got *serious* compression. It's probably got port timing that precludes it ever being a sport engine, but a low-compression head might be worth trying. It sure is pretty to look at and wasn't run very much. I think it made, maybe, four or five flights and never hit the ground. That's mainly because they were practice flights with one, very short combat wherein I was killed in, oh, about 45 seconds or so.

The venruri throat in this thing is huge. I wonder if it can ever be tamed, as the NVA is embedded in the side, not the middle of the venturi throat. A smaller venturi (thicker walls) would sorta bury the spray bar...

AMA 56239
"All of weather is divided into three parts: Yes, No and Maybe. The greatest of these is Maybe."

Jim P · Nov 18, 2004 05:47 PM

#4 source

LAST EDITED ON Nov-18-04 AT 05:54 PM (CST)

Kim:
Regardless of the head, the G21-35 will only run on bladder or case pressure with the large or "speed" venturi.
I do in fact have a suction venturi for the G21-35 unless I included it with the last G21 35 I sold-I'll look. As it is a sprinkler type, it is very difficult to reproduce.
The G21 35 is not a suitable stunt engine in any configuration. Fun to play with but nothing will make it perform properly.
The G21 should draw a nice price in the classifieds here on on Ebay. The proceeds could then be used to purchase a true stunt engine, the best for the money being the Brodak 40, OS LA 46, or possible the LA 40. Call me 282 4776 or e mail.
Jim

GLBahrman · Nov 18, 2004 06:36 PM

#5 source

>Kim:
>Regardless of the head, the G21-35 will only run on bladder
>or case pressure with the large or "speed" venturi.
>I do in fact have a suction venturi for the G21-35 unless I
>included it with the last G21 35 I sold-I'll look. As it is
>a sprinkler type, it is very difficult to reproduce.
>The G21 35 is not a suitable stunt engine in any
>configuration. Fun to play with but nothing will make it
>perform properly.
>The G21 should draw a nice price in the classifieds here on
>on Ebay. The proceeds could then be used to purchase a true
>stunt engine, the best for the money being the Brodak 40, OS
>LA 46, or possible the LA 40. Call me 282 4776 or e mail.
>Jim

I have a G21-35 that I have had since I was a kid 50 years ago. Anywhohow it used to be on a Flight Streak. A couple of years ago I called George Aldridge and asked if the motor was good for anything else because I would like to use it for stunt. Mine is the ball bearing motor. George said just add shims until it starts to break the way you like. So I did and it does. Been running a 2-4 break about 3 years now. Also I think I put a ST 46 venturi on it just because the original was damaged in a crash....Grins

Greg L. Bahrman

klelmore · Nov 19, 2004 08:47 AM

#11 source

Hmm... Add shims to where or what? I assume this is changing the port timing?

AMA 56239
"All of weather is divided into three parts: Yes, No and Maybe. The greatest of these is Maybe."

GLBahrman · Nov 19, 2004 11:53 AM

#12 source

>Hmm... Add shims to where or what? I assume this is
>changing the port timing?

Head shims are added to reduce compression. This helps to reduce run away and aids in finding the 2-4 break. Engines with to much compression will not 2-4 break with consistancy and some not at all. There are other factors also, venturi size, port timing, muffler size and fuel, plug etc. But adding head gaskets (shims) worked for me.

Greg L. Bahrman

Brett Buck · Nov 18, 2004 07:54 PM

#6 source

>The G21 35 is not a suitable stunt engine in any
>configuration. Fun to play with but nothing will make it
>perform properly.

Huh? I flew with one for a couple of years, box-stock, in a stunt plane. It worked fine.

Bear in mind, just like most ST models, a "g21/35" was not a spcific design, but a family of designs. I've never seen two alike. Mine had a flat-top piston and the "eyebrow" ports. Other types might work better or worse, but as a general statement "it won't work" is definitely not true.

Brett

Jim P · Nov 18, 2004 08:46 PM

#7 source

>I have a G21-35 that I have had since I was a kid 50 years ago. Anywhohow it used to be on a Flight Streak. A couple of years ago I called George Aldridge and asked if the motor was good for anything else because I would like to use it for stunt. Mine is the ball bearing motor. George said just add shims until it starts to break the way you like. So I did and it does. Been running a 2-4 break about 3 years now. Also I think I put a ST 46 venturi on it just because the original was damaged in a crash....Grins

Interesting. I perhaps spoke out of turn but my only experiences have been pretty much dead two cycle flat out runs on flite streak, mongoose, or Spyder type airplanes used at one time in slow combat and slow rat, etc. so I never tried to make them run in a breaking mode and couldn't imagine that they would.
I still assert that better choices are available for close to the money a nice G 21/35 would bring-I sold a pristine on on the bay a while back for $85.
PS At one time before figuring out that there are better at least more modern and easily replaceable 75MPH combat engines out there, a factory ST suction venturi cost me $15 and was hard to find.

Garf · Nov 18, 2004 11:32 PM

#8 source

There were a lot of versions of the G21 35 made over the years. I had an early one that was the sweetest running engine on the suction venturi that was supplied with it. I understand that is not true of the later versions.

SAVE ALL THE PIECES-Phil Brown

Brett Buck · Nov 19, 2004 06:21 PM

#14 source

>I still assert that better choices are available for close
>to the money a nice G 21/35 would bring-I sold a pristine on
>on the bay a while back for $85.

On that, you can be sure! I never said it was a good idea, just that it wasn't impossible. You certainly can get better engines by selling the ST and buying something else. If you are lucky, you mught get $120 or so for the ST, and for that you can buy TWO Magnum 36's - a far better stunt motor.

Brett

Howard Rush · Nov 19, 2004 01:19 AM

#9 source

I feel better now about your using a G.21 .35 for stunt. You had one of the substandard ones.

Brett Buck · Nov 19, 2004 06:23 PM

#15 source

>I feel better now about your using a G.21 .35 for stunt.
>You had one of the substandard ones.

I thought is was superior to those crappy runaway combat motors, but I guess it's in the eye of the beholder.

Brett

Nikyvee · Nov 19, 2004 02:59 AM

#10 source

LAST EDITED ON Nov-19-04 AT 03:03 AM (CST)

Amazing coincidence.... I just bought a used G21-35 from an ex-freeflighter's estate. I didn't know what I was buying. It is my first ST. I thought maybe I was getting a good deal at $35, but now it doesn't look so good. Jim P, if it is available, I would like to buy that suction-appropriate venturi from you; my engine also has the Wiiiiidddeee "combat" venturi. While I am at it, maybe you would also have a screw/plug for the crankcase pressure nipple, a backplate gasket, and a suggestion for a muffler. Mine has had the muffler ears ground off.... Thanks for any help. All of these comments have been helpful, I just wish I had seen them before... oh well.
You can contact me at: [email protected]
Nick Vanmatre, "learning I should get some info before I leap..."

njsupertigre · Nov 19, 2004 05:06 PM

#13 source

njsupertigre
Have a few suction venturi's for the S.T.35 (same as 46)
Just add two to three head shims and that will tame the engine down.
Venturi's $12.00 each + 2.00 shipping.
Bill Mazzoni
[email protected]