TCraft Lover

My Feedback: (1)

Have you read the tuning procedure in the glow engine forum. Maybe in the Super Tigre forum. It's pretty good and might help.

1QwkSport2.5r

I have read it many times. I've adjusted the carb by the book. The main needle is in a fixed orifice, so with the idle way rich as to not interact with the high end needle, set high end to peak then adjust for good idle. If the transition is rich, adjust the spraybar in small increments until transition is clean. Readjust both needles if needed. I think that's the basic gist of it.

I think I will swing up to Hub in Richfield and pickup a quart of SIG and try it again on the boat. If nothing new happens, I'll put it back on the test stand.

I've been through the fuel system 3 times. New lines X3, tried 3 different tanks, 3 clunks, about 8 different glow plugs and 3 different fuel blends. Either something with the carb is amiss or the hull is vibrating too much. I don't know. I'm kinda lost with it.

hsukaria

1QwkSport2.5R,
I have a couple of Super Tigres, a G51 and the other a GS40. Love them both.

I noticed that you said that you richened the HS needle 2 clicks from top rpm with no noticeable drop in RPM's. I am no engine expert, but I have always understood that the HS needle has to be richened from peak RPM's until the engine speed drops around 200 rpm's or more.

Once the top end is richened to 200-500 rpm below peak, get the throttle to idle and spike up the throttle. If the engine quits, the idle needle is too lean. It the transition stumbles and hesitates, then it is too rich.

Super Tigre manual also suggests pinching the fuel line temporarily at idle and waiting for the engine response. If the engine slows down or quits, then LS needle is too lean. If engine speeds up a lot after the fuel line pinch, idle is too rich.

You probably tried all these tricks, but I know all these were all I needed to get them adjusted. I did have to rotate the needle spraybar lately on the G51 since the transition was too rich. But that is the first and only time since I bought it 5 years ago.

Occassionally, at the beginning of flying season, I have to pump fuel through the carb at closed throttle and WOT to flush out the gunk from the carb. It helped a few times.

1QwkSport2.5r

Thanks for the reply. I have tried almost everything on this bugger. The break-in on the stand was painless and it didnt act up hardly at all. The reason I did not richen down off peak RPM is to have the high speed mixture set to "perfect" as to not create a needle-compensation scenario. ie: too rich high speed and too lean low speed or vice versa. I wanted the main needle peaked and then get the idle mixture set for idle and good transition, then richen the high speed mixture to drop the rpm a little. Since this is in an airboat and not an airplane, The prop will never fully unload. This boat doesnt go much faster than 35mph so I'm not going to be running anywhere close to pitch speed. So...

I can get the WOT mixture set fine, and I can get it to idle all day long. When set for both of these conditions, the transition is horrible. Moving the spraybar has little effect on transition which I find odd. I went through the carb and blew it out (it was clean, not a speck of debris, nor any castor goo plugging anything up.) I changed fuel tanks, clunks, etc. Either I'm an idiot or there is something amiss here. I am no stranger to finicky engines, though they dont exhibit their fickleness until on the craft they are to power. That tells me vibration may play a role in it. I do get some small bubbles. If I rest my hand on the fuel tank and hold the fuel line to the carb while at WOT, there are hardly any bubbles. I will mess around with it some more later today maybe. Got a few more things to try. I wish I had another carb laying around that would fit this engine just to try once. I know its possible even with the crappiest of carbs to get some decent production from the engine, but this is the hardest time I've ever had getting an engine to run reliably. I am going to try some different fuel tank padding material and see if that makes a difference or not, as well as dropping the fuel tank centerline some to see if that does anything. Fuel does not flow from the tank through the carb and into the engine with the tank full and the throttle fully open so syphoning is not happening.

edit:
It seems to me that I'm not the only one with an S90/S90K carb that is a bugger to tune.. here's a thread about it: [link=http://www.rcuniverse.com/forum/m_8867384/anchors_8867384/mpage_1/key_/anchor/tm.htm#8867384]S90/K w/ Perry carb[/link] I will go this route if I need to, though I will keep working on the ST carb. My patience is thin though, as I've been through a similar problem with my K&B .65 - Mismachined carb parts makes the midrange so obscenely rich no amount of adjustment would clear it. Both of my .65's are getting Perry carbs when I can afford to drop $100 for 2 carbs. Since I have airboats with no method of retrieving the dead boat except a fishing pole, I'd rather have the engine running superb before going back to the pond because its NO fun casting out 20 times to retrieve the boat. Incidentally, I had better running from my K&B's. I could feather the throttle through the midrange to get it to not quit on me.

Blah.

hsukaria

Your problem sounds too odd for me to know the answer. I am not an expert. But have you tried the carb O-ring? Maybe there is an air-leak. Also, any loose screws/leaks elsewhere like the crankcase backplate? I am not saying that is your problem, but who knows?

I had to put a piece of fuel tubing on one of my engines' HS needle to stop an airleak there.

1QwkSport2.5r

no air leaks. RTV on the top/bottom of carb base o-ring. My original thought and what I still think the problem may be is the detents on the needles are rather coarse. 1 click may very well need to be more like 2 clicks instead of one. As Pé said in the other ST thread in "Glow Engines" is oftentimes the optimum setting is passed by going too much at one time. I fine tune 1 click at a time since the retention clips on the needles will not hold the needle between detents. I almost need to file the detents down a little so it will hold between "clicks" I think the idle mixture is very very sensitive. I have a few other things to try as well, but that will be for another day. I have a strong hunch it has something to do with the carburetor and perhaps within its fuel metering circuitry. Something is amiss, I think.

hsukaria

Well, good luck and keep us posted.

1QwkSport2.5r

As I get more time to run the engine at home, I'll try more things. I need to eliminate the bubbles for peace of mind, and maybe make some adjustments on the carb and spraybar. When I get to the bottom of the quitting, I think I'll get to the bottom of why its such a pain to get a good idle, transition, and WOT rpm.

iskandar taib

My Feedback: (5)

Silicone does contain silicon.

Can't say much about whether Armorall kills plugs, but I can tell you what happened to me when I used too much. You're supposed to use a couple drops per gallon, I used a squirt in a pint! The fuel tubing would NOT stay on the needle valve nipple. This was at the Frozen Finger contest one year (Slow Combat, first weekend of the year, Chicago! Freezing cold..). It took cleaning with a brillo pad to get tubing to stay on that needle valve nipple ever again.

Iskandar

iskandar taib

My Feedback: (5)

Kinda late to the party here.

Some sources of materials I've heard about in the past.

Methanol. Paint stores. Sherwin-Williams paint stores in particular. I confirmed it by paying them a visit. Didn't actually buy any because I had lots of fuel.

Castor oil. Old Rhinebeck Aerodrome buys it in HUGE quantities. Why? They run vintage WWI aircraft that use rotary engines. These have a total-loss lubrication system using castor oil. And they'll sell you a gallon or so, fairly cheap from what I've heard.

Nitromethane. Get to know a drag racer. At the end of the season, they often have a gallon or two left over, which they might sell to you. Nitro's also available at drag races, but it doesn't cost any less than elsewhere. I imagine they'd have methanol as well - some classes use straight methanol, some use a methanol/nitro mix and some use pure nitro.

Mind you, all this information's at least 10 years old (I don't live in the US any more).

Search on alibaba.com and you'll find lots of companies selling nitromethane. All in China. Comes in big (200 liter) blue plastic drums. Be careful, there was talk some time ago about contaminated nitro making its way into some commercial RC fuel and destroying a number of engines. Had residual acids in it.

Another story - Red Max fuel had a promotion saying that they'd send you a quart of fuel - any fuel you wanted - if you put an ad for them on your website. I did. I asked for 70% nitro boat fuel. They sent it. I used it for mixing 1/2-A fuel.

Iskandar

1QwkSport2.5r

I think I found my perfect fuel mixes, and no dyes required. I have 2 different gallon jugs that are different colors even. 1 for Aero and 1 for Cars. The methanol is pretty blue to start with so getting a color other than blue is tough so I wont try dying it anymore.

Cars: 20% nitro, 12% castor, remainder methanol with 1 1/2 squirts of armorall. End cost = $20 a gallon vs. $36 at the hobby shop

Aero: 5% nitro, 20% castor, remainder methanol with 1 1/2 squirts armorall. End cost = $12 a gallon vs. $30 at the hobby shop in quarts. (they wont order gallons from SIG which is what they carry with castor in it)

I wrecked a gallon of 5% nitro fuel because I tried using silicone shock oil for my rc cars and I dont think it was pure silicone. Anytime I tried running it, my engines wouldnt run without glow attached and that was perfectly tuned. Once I switched to using armorall (I needed to use a smidge more AA since they reformulated it and was still getting a lot of bubbles) I found much better reliability with my engines.

I did try running FAI fuel in my SuperTigre using 3% acetone but I got 800-1000rpm more using 5% nitro instead so I'm going that route. I still have about 2 gallons of methanol, 1/2 gallon nitro, and about 1/4 gallon castor left. Time to restock on castor oil soon!

iskandar taib

My Feedback: (5)

Forget dyes - I recall someone was selling fuel perfumes. Anyone remember who it was? It was on some web site.

Iskandar

hsukaria

I heard about the perfumes for the stinky gasoline engines. The gas engines really stench up the whole club field when they fly.[:'(]

1QwkSport2.5r

My rc car hobby shop has fuel perfumes for glow fuel but I've never tried them. Rumor has it they don't work very well. Besides, I personally like the smell of castor exhaust.

On the fuel dyes, I tried food coloring which did work and didnt affect tuning but the amount of red or yellow needed to overcome the blue color of the methanol made it impractical in my opinion. I think I may try a small squirt of men's cologne in a tank of fuel to see if that does anything just for experimentational purposes.

iskandar taib

My Feedback: (5)

Doing a web search for "fuel perfume", I got this:

http://www.cheap-perfume.com.au/mens...el-for-life-2/

"cheap-perfume.com.au"... ROFL...

Iskandar

1QwkSport2.5r

Oh my.. that made me smirk! LoL... At first I thought it was cologne that smelled like diesel fuel.. (I know a few guys that might wear it if it indeed smelled like diesel fuel) I was wrong! haha.. Good one, iskandar!

On a day I dont work until the cows come home, I might throw a spritz of "Cool Water for Him" in the fuel tank and give 'er a go..