hsukaria

Have you tried rotating the jet assembly? That is something unique to ST engine.

Sorry, I don't have experience with Perry carbs.

flyingspig

My Feedback: (7)

Dave,

My ST 4500 G works a lot better with Perry Pump(vibration type) / F plug combination.  Make sure to use low oil (10%) and no Nitro (0-5%) fuel.  It's original carb doesn't have much throttle range either.  It will be a good idea to replace with OS carb too.  If you want to spend more time flying, go with gas.  

Chris,    

hsukaria

flyingspig, the OP is working on the .90, not the 4500. So, for that smaller engine, regular glow fuel is needed. Based on advice I got here, 5% nitro will help in the transitions, it helped my ST51. If after switching to 5% nitro fuel and re-tuning didn't help, then I would consider rotating the carb throttle assembly (not sure of the exact name) very slightly to lean or richen the transitions. I have also been told that muffler design will affect transitions, so, that will have to be accounted for in the tuning.

DaveFri

My Feedback: (7)

I am using 5% nitro,McCoy 59 plug,APC 13x8, have rotated the spraybar slightly to try to fix the midrange with little help.Top end is good and it has a pretty good idle but the transition is not so good.When you get a good solid idle the midrange is sloppy.Have heard that a OS7D is the carb to get(hard to find these days) or the Perry carb.This is my second ST-90K and both are sloppy in the midrange.

Dave

hsukaria

Sorry Dave, that's all I know. Those tricks worked on my ST G51. Maybe some of the experts here can help. I'm curious to find out what ends up solving your problem.

DaveFri

My Feedback: (7)

Well,i've read pros and cons on the ST-90K carb.I have a Perry ordered.We will see how that works.We have a few guys in my club and they have a few ST-61K and those run great.!

1QwkSport2.5r

The 51, 61, and 90 uses the same carburetor. Only real difference is if the spraybar is round or milled flat.

The proper procedure to set the ST carb is simple. Peak the main needle, do not richen from peak. Drop to idle. Adjust idle mixture to sustain good idle, under 3,000rpm. If transition is rich, rotate the spraybar clockwise 1/8th turn. Recheck transition several times. If still rich and snotty, keep rotating the spraybar in small amounts until it transitions good. Until it has some time on it, it will be rich in the midrange. When it gets good and broke in, the spraybar will have to go back to straight in. Once idle speed is good, and transition is good, go back to WOT and richen the top end so a quick pinch of the fuel line gives a slight rise in WOT rpm. Go fly.

Bax

My Feedback: (11)

We wind up posting this a few times every year:

http://www.rcuniverse.com/forum/m_1579985/tm.htm

This is the process we use. Also, prop the engine so that full-throttle running gets you near 12,000 RPM for best power and throttle handling. Many people use too much propeller, and so have a too-low RPM at full throttle. While the engine will run well down at 10,000 RPM or so, you'll have a lousy transition. Also, don't try to idle too slowly. Anything under 2,500 RPM is considered good.

Try an APC 13 x 8 propeller and see how it runs. You'll get lots of power and better throttle handling.

blkangus

My Feedback: (1)

Hi All,
Perhaps someone can shed some light on a problem I'm having with a G75? It starts and runs fine on the bench, but when mounted (inverted) in the plane, I can't get it to start. Someone told me I may need to flip the plane over to get it running...maybe this engine just does not start unless right side up? Other ST engines I have seem to like a lot of fuel to get going, and inverted the fuel runs out the carb before getting to the engine. The only other diffrence between the bench set up and the plane is that the plane has a fuel filler valve, maybe this causes some trouble with air leaks?
I'm happy to keep tinkering but maybe this is just the wrong engine for the plane? Any advice would be much appreciated.
Best,
Glenn

1QwkSport2.5r

Best advice I can give - get rid of the filler valve to reduce that variable. Next, inverted engines rarely start for me without an electric starter. I get fuel to the carb, and while turning the engine over with the starter I plug the exhaust momentarily. Usually once or twice is enough.

OR flip the plane upside down to get it started. The engine doesn't know or care if its right side up or upside down. Air/fuel, glow, and compression is all that's needed for the engine to run.

Being inverted, be sure you're using a HOT glow plug.

Bax

My Feedback: (11)

An inverted engine can be a trial. Typically, they tend to flood out very easily. If fuel runs out of the carb before you can crank the engine enough, then you may need at least put the plane on a wingtip to start it. Starting in a cradle while inverted would be best. I once had an engine that would be very difficult to start inverted. Even an electric starter took a while...forget about hand-flipping! Invert the airplane and it would start right off every time.

You need to be careful about priming the engine so that it's not flooded. Of course, if it's too "dry" it won't start either, and then it will be too easy to overprime. The best thing to do is get the engine well broken-in on a test stand, and get the carb well set up. Then you know it will run properly. Put it in the plane and work out the starting technique.

Remember, in the model, with the airplane upright, the centerline of the fuel tank should be level with the carburetor or no more than about 3/8" lower. Don't get it higher or flooding will happen too easily.

blkangus

My Feedback: (1)

Looks like it was just a leaky fuel filler valve after all. I by passed it and she started right up and ran fine.
This is my first inverted engine install, so I guess I had kept thinking "worst case" and dreading any more work on a plane I have spent way to much time on already...time to fly it!
So for the record... 1 bad "great pains" fuel filler = much headache
Any recomendations on a trouble free fuel filler? the cowling on this plane is a real PITA to remove /replace or I would just forget it.
thanks,
Glenn

hsukaria

I would use a third fuel line with a plug at the end or a fuel button. Make it accessible from the bottom of the cowl if using a plug, or with the fuel button you can mount it on the cowl or fuselage. Maybe even try to fit the new fuel button in place of the filler valve.

It's good that the problem ended up being the fuel filler valve (I know another guy who had the same exact problem). If it weren't the fuel filler valve, then another solution would be to use a fuel regulator like Cline or Iron Mountain. These have been discussed quite a bit in different forums. I don't have experience with these, but I understand that they also cure any flooding problems with inverted engines.

turbo.gst

My Feedback: (8)

I think that the fuel tank placement is more critical for Super Tigre's than some other brands. I set mine up with the needle valve c/l the same level as the fuel tank c/l. Many times that takes throwing the engine / fuel tank positions on the plans to the wind. With the proper setup, I have great running ST's. I did get a couple of the ST 2300's that had the 'dogleg' groove on the carb barrel that did have some midrange issues. I bought the replacement barrel and they are fine. I am a big Super Tigre fan having them from the X-11 to the 4500.

hsukaria

The tank placement, as you say, is critical. But for most of us that have ARF models, there usually isn't much room to maneuver the tank height, so you better hope that the ARF manufacturer did their homework and designed it properly. I've had at least one ARF that did not have the tank height correct and no room to adjust tank placement.

turbo.gst

My Feedback: (8)

You are so right about the poor tank positions on ARF's. Even on some kits the tank placement seems like an after thought. Its sad, because you know the engine will be blamed when it can only do as well as it is setup / adjusted. You put a ST engine with a proper tank position to engine setup and you have an awesome day at the field everytime.

hsukaria

I have two ST engines (GS40 and G51) with proper tank placement. I got them dialed in perfect and using MACs one-piece mufflers for lightness. I had a sluggish (rich) transition in the past, and the guys here told me about using 5% nitro fuel and that solved it.

fujiman

My Feedback: (133)

Hi guys. Have question about turning the or adjusting the spray bar assy. to lean or richen midrange on S.T.'s. Which way do you turn spray bar assy. to lean midrange and which way to richen midrange???? Thanks

1QwkSport2.5r

It doesn't really matter which way you rotate the spraybar, although I always turned it so the fuel nipple was aimed toward the mount lug.

hsukaria

So what you are saying is that you can only lean the mid-range, not richen it by rotating the spraybar? It makes sense to me, but I just want to make sure.

1QwkSport2.5r

The proper position of the spraybar is always straight in. My S90K was the one picky one of the bunch needing a really tweaked spraybar for over 2 gallons of fuel. After that it had to go back to straight in. Any adjustment from straight in will lean the midrange. More adjustment, leaner mixture. If your midrange is too lean with the spraybar straight in, there is a fault elsewhere in the fuel system IMO.

hsukaria

My ST G51 has the spraybar straight in. I got around the rich mid-range by following the recommendation made here and switching fuel to 5% nitro fuel and re-tuning the engine. The mid-range now is just right.

1QwkSport2.5r

I put bowman rings in my g51 and S29 and neither of them needed the spraybar adjusted. They do have the round spraybar so that may make the difference. My S90K has a flat milled spraybar (which makes more rpm than the round ones).

jeffie8696

Just an update for the club. I installed my Super Tigre V60 on my Great Planes Escapade and its a really good fit. With the light weight of the V60 and the excellent power I am really happy.

hsukaria

You have to be patient with us un-enlightened pedestrians, but what is the V60?

My Escapade has lived most of its life with the ST G51 (Chinese) with the MACs one-piece muffler, but it has also run the OS 55AX, Irvine 40 with tuned muffler, and Norvel AX-40. I think it will remain with the ST51 from now on.