CLBetten

My Feedback: (16)

Another method I've used to determine whether the idle mix is too rich or too lean is to compare the transition off idle both with and without the glow driver attached. If it's lean the glow driver will have little effect. If it's rich the glow driver will greatly increase the quality of the idle and the transition from idle.

Charley

My Feedback: (2)

Virtually identical. Lots of parts would interchange. I was flying STs in 40-60 size birds when Indy RC was selling both ST and Como engines & parts. Comos cost less, ran as well. World Engines was the US ST distributor. WE put a stop to Indy's selling the Comos, threatening to sue. I bought a lot of ST parts at bargain prices when Indy quit selling them. Long time ago.......

CR

CR

FlyerInOKC

My Feedback: (6)

I got an ongoing love affair going on with ST engines. Lately I have been collecting discontinued Top Flite manifolds for their in-cowl mufflers. I love the ST .75 and plan to use this engine in several Top Flite Gold Edition warbirds. I have a .75 in a to be completed TF 182.

AllModesR/C

I tried installing a number six glow plug and that did nothing. Tried richening up the low speed which also was a fail. The engine still "hangs" when the throttle is closed to idle and won't idle more than a few seconds without quitting. Also has a hesitation when transitioning from idle or 1/4 throttle to WOT. It only runs decent at half or WOT. Any ideas? Or better yet is there somebody around Chicago who can lend me a hand in tuning it? BTW it is mounted sideways in the plane.

Hobbsy

My Feedback: (102)

Is your LS needle set about right there?

AllModesR/C

No, it appears to be pointed down. What do I turn to adjust it?

1QwkSport2.5r

The picture FDF posted is showing the carb from the bottom (the neck that fits into the engine) and is referring to how far the needle extends into the "cats eye" orifice. It sounds to me as though your needle settings are still out of whack or the carburetor is dirty.

jeffie8696

Could be a fuel issue or any number of other things like a vacuum leak

FlyerInOKC

My Feedback: (6)

If you haven't already done it I would disassemble the carb and boil the metal parts then after drying completely reassemble with new "O" rings/seals. If the tank is accessible first pressurize it and submerge in water to check for leaks. Then you might replace the fuel lines, add tubing clamps or cable ties to prevent air bubbles, and install an inline fuel filter.

AllModesR/C

What model carb is this and where can I get new "O" rings for it?

FlyerInOKC

My Feedback: (6)

Without knowing what markings are on the engine I can't tell you which carb it is but I would check the LHS to see if they have any stock ST parts. There are usually only two "O" rings, one where the body of the carb meets the engine and one for the idle needle. I buy most of my "O" rings at a local industrial gasket shop with a large selection you may be able to find replacements at an auto parts store. Take the old rings with you and try not to damage them in the removal. The S.T. website does have some exploded view you might compare with your carb.

AllModesR/C

The previous owner put some kind of sealant between the carb and engine connection area. So I'm pretty sure there are no air leaks there. Appears that I bought his problem. With my limited knowledge and ability I am at a loss as to what to do with this plane. I know that if I disassemble the carb it will solve nothing as I've already been down that road with another nitro engine I had the misfortune of owning. Is there somebody I can just send the engine to and pay him to get it running right?

1QwkSport2.5r

I would work on it for you for free if you paid postage both ways. It's winter where I live and expecting more snow soon, so I may not get to run it for awhile...

AllModesR/C

Sounds good sir. PM me your address and send it this week. Have nothing to lose. No rush either.

1QwkSport2.5r

A PM is on the way.

1QwkSport2.5r

Going a different route with this post.

Working on an S40 for a fellow member here that had troubles adjusting it and getting it to run right. I've determined it to have the wrong idle mixture needle and the main needle is badly bent. The idle mixture needle is not visible at all in the discharge orifice in the spraybar even threaded all the way in. Because I do not know how many times the main needle has been bent (it is the bent-wire type needle valve - old style ST Mag carb), I do not feel comfortable trying to bend it straight again. It may work okay as-is, but the idle needle clearly needs to be replaced with the proper needle. It is clearly obvious why the engine did not run correctly. I'm not posting this to pick the owner apart - I'm posting this in an effort to source the proper needle so the engine will run properly for the owner.

If someone has an idle mixture needle that fits the old style carb (the idle needle is not recessed into the throttle arm as is done with the modern carburetors) and can part with it... Please let me know. The only ST carb I have of this older style is on an S29 and would be too small anyway; otherwise I'd take the needle off mine and put it on this fellows engine to get him operational.

jeffie8696

There is a guy on ebay that sells them fairly cheap, I got onw the other day and it looks good

1QwkSport2.5r

I've seen the main needles (bent wire type), but haven't seen any idle mixture needles. I'll have to do some more looking around. Does your buddy Bruce sell parts?

Hobbsy

My Feedback: (102)

This Super Tigre G-21 .46 had the long bent HS needle, as you can see I put a knob on it. Those needles usually had a collar on the end of the spray bar to seal and keep the needle from shaking and turning.

1QwkSport2.5r

Some pics of the carburetor I speak of. First picture is a modern Mag V ST carb from a Italian GS45 ABC. Rest of the pictures are of the suspect S40 carb. You can see the needle in the first picture, but not in the second picture.

The spigot that goes into the engine is 14mm. I'm probably going to try sourcing a whole carb for this fellow. Both needle holders are bent and one detent clip for the low speed needle is broken.

1QwkSport2.5r

Yes, this S40 carb has the collet nut to retain the needle and my little S29 has the same type of needle/collet retainer. I found a few Carburetors on eBay, but some don't list the spigot size and the one that did was 12mm. This jewel is 14mm.

Edit: the low speed needle in the S40 carb is 19.5mm from base of brass thumbscrew to the tip of the needle. Pulling the low speed needle from my S90 shows a 26mm needle and is the proper length in the S40 carb.

jeffie8696

If you give bruce a shot he may be able to find something in his huge pile of engines

1QwkSport2.5r

I'll try shooting him an email and see if he has anything he can spare. Thanks.

1QwkSport2.5r

I sent an email to Bruce through his website but didn't hear back. If he has a carb, I'll pick one up as a spare... In the mean time I found a parts engine that I'll buy and part out. Should be a win-win for everyone involved.

jeffie8696

He may be out of town on a trip