Flyboy Dave

My Feedback: (21)

Hobbsy....look at these links. There is something strange. Nowhere on the S.T. carb or
needle does it show the spring on the main needle. If you look at the bare new needle
it shows the o-ring, and it states the o-ring is fitted inside at the bottom of the needle
like mine. In fact, no where does it list that type of spring for sale, and it doesn't show
or list for sale that fat inside spring you show.

Look this stuff over and see what you think. The 40, 46, and 51 carbs are the same carb.

http://www3.towerhobbies.com/cgi-bin...I=SUPG1803&P=Z

http://www3.towerhobbies.com/cgi-bin...?&I=LXFY19&P=Z

http://www3.towerhobbies.com/cgi-bin...I=SUPG1803&P=Z

http://www3.towerhobbies.com/cgi-bin...XFY19&P=Z#tech

http://www3.towerhobbies.com/cgi-bin...P=Z#partsusage

Flyboy Dave

My Feedback: (21)

.....look at the tech notes.....there is no spring here, just the o-ring.

http://www3.towerhobbies.com/cgi-bin...XFY19&P=Z#tech

I figure the o-ring at the bottom of the needle butts up against the taper on the nozzle
and acts as a stop so the needle can't be screwed in too far and damage the "cat's eye"
in the middle of the nozzle. I can't figure any other reason for it being at the bottom of
the main needle. I have seen a needle that was screwed in too far at the field, and the
end of the needle broke off and was stuck inside the nozzle, rendering the carb inop.

Nowhere on a S.T. carb that I see does it show or list a spring on the main needle, and
I have never seen a spring on a HS needle on a model carb. Surely someone will find one
and say I'm wrong, but that's par for the course.

Don't ask me, I just work here.

Jezmo

I am not going to argue with the "Experts". That picture I posted was of a carb taken off one of my engines and had never been disassembled before that pic was taken. In fact the carb had never been off the engine before I tried to help someone out. All of my ST carbs have this spring and yes it is normally hidden far up inside the knurled thumb nut and yes the O-Ring is placed over the the needle after the spring is on. If they are slid on as far as they will go they are pretty much hidden. The spring pushes the O-Ring into the chamfer creating pressure on both sides of the O-Ring in order to seal it on both surfaces. You can run yours any way you like but I can assure you of one thing, I am the one who posts time after time in thread after thread that there is NO PROBLEM with the SuperTigre MAG carb. Maybe there is a reason I don't have problems tuning SuperTigre's like some other folks do. Nuff said and I am out of here.

Hobbsy

My Feedback: (102)

Dave, every single SuperTigre carb I have is like that except my G21-.46. I have two .51s, two .90s, a .61 ABC, a .45 ABC, a new 2300, an ancient 3000 and the 4500 pictured above. Every carb has the spring and O-ring.

DarZeelon

Quote:

ORIGINAL: Hobbsy

Actually Dar the O-ring a pretty tight fit over the fat part of the needle, you feel a definite drag as the taper approaches 75% of the way into the O-ring.

Dave,


...But I can guess its fit is not too tight, so the spring is able to push the O-ring out and keep it compressed against the 'well' in the end of the nozzle tube, as the needle is withdrawn when opened.

This is how the seal is supposed to be achieved.

Jezmo

I have noticed in many posts Hobbsy has indicated he has no problems with SuperTigre carbs. (Yeh, I know most are converted to diesel ) It seems from his last post that most of his ST's have the spring. I have also noticed that there are some carbs I have worked on that have had this spring left out (not sure if the owner lost it or the factory left it out by mistake[:@]) and they leak fuel from the main needle area and are generally more difficult to tune. Not impossible but more difficult, especially with the transition. I have helped a number of folks at our field tune their ST carbs showing them some of the fine points to getting one right and I have noticed a couple without the sping and when the spring was put in the engine ran and transitioned better.

I am not trying to pull anything over on anyone and that is the truth on that being an unmolested ST carb I took the pic of. I think Hobbsy's observations back that up. Guys, open your minds; maybe the missing spring is part of the reason for some ST's being HARD to tune and others being creampuffs. Just a guess.

One other thought, why not get Bax to look into this and see why some seem to have the spring and others do not. It might be a quality control issue (Possibly the springs are being accidently left out on some engines at the factory[:@]) and bringing this to his attention might improve the quality of the ST line.

Jezmo

Great explaination Dar. You understand what is happening and how that is designed to work.

Hobbsy

My Feedback: (102)

Thanks Dar & Jez, here are the needles off of the 8 SuperTigre carbs I could find, there are two or three more on non SuperTigre engines. At least one of these was bought as a replacement and I have some that I bought from people who replaced them with other brands of carbs. It looks like all the carbs should have them. Hopefully Bax will see this and comment.

Woops, need picture. My Missus is at work so I need something to do anyway. The O-ring on the needle closest to us was stuck down in the NV, my guess it was stuck from when someone soldered the extension on to it. That one was on a well used .90 that I bought in the MarketPlace.

Jezmo

Yes sir, that is how mine look. I sincerely think the lack of a spring may help explain why some people experience mid range problems with their MAG carbs. When the the throttle is brought back to idle the air leak around the O-Ring will be causing the most amount of problems because of the idle needle blocking the fuel channel and therefore the lower amount fuel draw can't overcome the leak as well. The idle needle will then need to be opened more in order to compensate for the leak. When the throttle is increased the fuel mixture will now be too rich and cause the mid range and transition problems associated with the ST carb. I have been running SuperTigre's for over 30 yrs. and as far as I can tell have never owned an engine that was missing the spring. I am now starting to understand why some people have these problems and others do not.

the pope

Ok its the pope here again ( you know the guy with the original prob.) Now the concensis is that there is a spring behind the o ring, is that right ? Now how does one remove the o ring to see if there is one there ? I filled the needle up with lube hopping that it was just dry and stuck down there, now this hasnt made it budge. I have shaken it and it still wont move , what do I try next remembering I dont want to bugger up the o ring. Thanks cheers the pope

the pope

Yee Haaa I finally manage to free it all up and the spring is in there , now I just need to fire it up and see if it still leaks ( I think the pope needs to do a bit of praying to the rc gods here.)I dont know when that will be ( the starting up bit not the the praying) and will get back to let you and let you know how it goes, Thanks for everyones time and effort cheers the pope.

downunder

I only have 2 ST's with carbs, one's a NIB early round head S45 from the 80's and the other is a later second hand S45 so I got curious. I got a bit of K&S 1/8" tubing, slid it over the needle and pushed down to see what I could feel. All I can say is well bugger me, there's an O ring and a spring down there .

the pope

Perhaps ST should update ther exploded diagram of their carb to show all of whats in their stuff. I could have sworn there was no spring behind the o ring but I was wrong ( theres a first ) It would have been handy to know what should be in there and not just guess or rely on the internet with its own dangers of getting led down the wrong path . cheers the pope

Flyboy Dave

My Feedback: (21)

I think I got this figgered'....

....I bought this engine new for a friend along with a Tower trainer. He has kept the plane
in his possession. I just rebuilt this carb a few days ago, because we crashed the plane.
The spring in the carb barrel is not the one listed in the parts break-down....that one is
supposed to be 6mm thick, mine is 3mm. I think my spring is supposed to be the one on
the HS needle....but it works Ok as a barrel spring.

Now, my HS needle has an o-ring down at the bottom of the needle....I can see it down there
with my bore light. So, my best guess is this carb was assembled incorrectly from the factory.

The spring and o-ring for the HS needle are out of position, and the proper spring in the barrel
is missing. Strangely, the engine ran perfectly....like a top.

The 6mm barrel spring is supposed to fit over the spraybar. Mine butts up against the
side of the spraybar. If you look closely at pic #1 (enlarge it) you can see where the little spring
was riding against the side of the spraybar. And strangley, the barrel spring pressure and
action are proper.

Flyboy Dave

My Feedback: (21)

...my "barrel spring" fits perfectly on the HS needle, just like Hobbsy's picures, but the
o-ring is down at the end, inside the HS needle assy. [:@]

Hobbsy

My Feedback: (102)

Daver, you'll have fun getting the O-ring out, I had to drop a couple of those needles on the work bench like a dart to get the O-ring and spring to come out.

Flyboy Dave

My Feedback: (21)

I doubt that I can get it out....I don't have the weight of the spring to work against
the o-ring. I might be able to leave it in there and just put a spring and new o-ring
on top of it....I might have to cut a couple coils off the spring if the "stack" is too much.

I'll have to run the rebuilt carb and see....it was fine the way it was. See the parts here
when I finally got the carb apart....the 6mm barrel screw is AWOL. [:@]

Sorry about the confusion on my part, Fellas....I got fooled on that one. [sm=red_smile.gif]

FBD.

Hobbsy

My Feedback: (102)

You might get it out with a T pin but no matter how you get it out it ain't gonna worth much. I grab up all the St carbs I can get, they are simple, straight forward and work very well.

Flyboy Dave

My Feedback: (21)

....good idea on the T-pin. I might be able to get a hardware store spring and make it
work for a barrel spring. I guess the spring and o-ring come pre-installed in a new
main needle....but they make no mention of the spring in the parts pages.

I always thought S.T. carbs worked great, and were real easy to adjust as well. I've
only owned one .45 ABC, one old ringed .60, three 3000's (but only ran one) and this
little ringed .40. The little .40 is one of the best running engines you could hope for.

I got it all rebuilt and cleaned out....I had to wait a week for the exhaust manifold. I
gotta get the new Tower trainer built too. That .40 (for fifty bucks) is my most highly
recommended engine for a trainer. All the parts are available too. It would take some
doing to wear the little ringed engine out. They would be excellant for a twin too.

We stuffed the trainer straight in. I got three sets of gears to put in the three cabin
148 servos....they were new, we stripped them all. I can't remember what happened to
the wing servo....it probably survived.

Fun, fun, fun.

Flyboy Dave

My Feedback: (21)

....proving once again, there's more than one way to skin a cat...

....I couldn't fish the o-ring out, so I drove out the needle. It worked out OK because
the o-ring is in perfect shape. A new spring for the barrel cut out of a ball point pen and
I'm in business. I put the needle back in, gave it a little squeeze with some side cutters,
and gave it a drop of assembly (penetrating) Lock-Tite, and it's good to go.

Is this fun, or what ?

FBD.

pilotpete2

Hi All,
After finishing reading the entire thread with interest. I checked my G90 that was been flown all season and is just getting broken in.
I could not remember seeing the spring and "O" ring when I had the needle out prior to now, but low and behold, I just checked and sure enough when I removed the needle the "O" ring and spring were halfway down the needle. It's nice to know it's assembled correctly[8D]
Cheers to All,
Pete

Bax

My Feedback: (11)

With VERY FEW exceptions, all SuperTigre high-speed needle valves will have the spring and o-ring. They are not listed as separate parts, but come only with a complete needle. It's possible to lose an o-ring and/or spring when the needle's removed from the engine if they happen to be a bit loose. That's most likely how different engines will have those parts missing when a second owner gets one.

Flyboy Dave

My Feedback: (21)

Bax....what do you think about mine, with the main needle spring in the barrel, and
the o-ring at the bottom of the HS needle.....mis-assembled ?

blw

My Feedback: (3)

Good pics, Hobbsy. That pretty much settles it. Eight needle valves? I think that is a first around here.

Hobbsy

My Feedback: (102)

Thanks Barry, as I mentioned above I scarf up all the orphaned ST carbs I can find. For some strange reason riding in a mail truck always fixes whatever issue the original owner thought it had.