rc34074

My Feedback: (5)

i am new with gas engines. i have a g38 which appears to be an older model with the steel prop hub. it has a new carb which i bought last spring at toledo from hangar 9. it also has the twist mount for the carb.

i have been having a problem with the engine not coming up to speed in the air. it runs about 7300 on the ground with a zinger pro 18-10 prop. but when it is in the air it is not coming up to that rpm, at least it doesn't sound like it does to me, and the plane is not performing. the carb is hanging outside the cowl with the plate that has the little air vent hole facing toward the front at about 45 to the air flow. it has an rcj8 plug, which is carboning up. i just got a new plug from hangar 9 and it is an rcj7.

what do you guys think is happening here? will the rcj7 plug help? is the air flow affecting the carb?

thanks

ed

STUKA BARRY

THE NEW PLUG YOU HAVE IS FOR THE ZENOAH G-62. THE THREADS ARE MUCH SHORTER. GO TO YOUR NEAREST NAPA AUTO PARTS STORE AND GET AN RCJ8 PLUG. GAP IT TO .022 AND INSTALL IT. YOU ARE RUNNING THE RIGHT PROP. IT MAY BE LEANING OUT IN THE AIR INTEAD OF RICH. TURN THE HIGH NEEDLE OUT AN 1/8 OF A TURN AND FLY IT.

Antique

My Feedback: (4)

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rc34074

My Feedback: (5)

thanks for the replies guys.

i compared the rcj8 plug to the rcj7y which is the new plug i got from horizon. the box the rcj7y plug came in is marked "zen6242 g62/38/45/445 spark plug, c8596." the threaded length of the rcj7y is the same as the rcj8, but the length from the end of the threads to the end of the formed electrode on the rc7jy is about twice as long as the rcj8, so i would think that the rc7jy would be a hotter plug, which should help the over-rich condition. it is rich because the rcj8 okug i was using is getting carboned up- that is, there is a lot of carbon building up on the plug.

the new carb i bought at toledo is the wt338 carb.

rcign-is your advice about closing the hole in the brass plug only for the wta6 carb? or does it apply to the wt338 also? i have been using 93 octane gas with amsoil lubricant at 50:1. the high end needle has to be almost closed, as you say above, to get the engine to run 7300 on the ground.

also- the small hole in the plate over the diaphragm is facing forward into the air flow. would it be a good idea to turn the plate around 180 so the hole faces to the tail of the plane? is it possible that the air flow when flying is pushing air into this hole and affecting the diaphragm? would this make the mixture richer?

thanks

ed

Fighterpilot

My Feedback: (2)

Most of the engines that we run, that have the carb hanging out in the air, go rich once we take off. It has to do with the air flowing over the carb opening at a higher rate and causing a vacuum that does not allow the carb to suck as mush air as when it was running in a static position on the ground. You might try a velocity stack with the opening pointing forward in order to force more air into the carb or just try leaning the motor out until it does not 4 cycle or sputter after you take off.
As far as the plug fowling out, it's because you are running the engine too rich. As you said, it goes rich after you take off. Just lean it out until it stops gurgling once in the air. Use the plug that the engine manufacturer recommends on your 38, which I believe is the RCJ8. I always gap at about .030 and have never had a problem.
What gas/oil mixture are you using? I wouldn't go any higher than 32 - 1. Too much oil could also be a cause of plug fowling.
Good luck

Flypaper 2

Both plugs have 3/8 long threads. Thats what the J stands for. The Y stands for extended nose. On Champion plugs, the higher the # the hotter the plug, although I would go with the RCJ7Y as it puts the spark further into the combustion chamber.

rc34074

My Feedback: (5)

thanks for the replies- will try the rcj7y. would have tried it today but felt too crummy to go to the field .

Fighterpilot

My Feedback: (2)

Although your engine may run better with a new plug, the problem you described above regarding the engine going rich in the air is not the result of a bad or improper plug. The excess fowling may also get somewhat better by changing the plug; however, your problem is that you are running your engine too rich per your own description that it sputters once the plane is airborne and flying at speed. You need to lean out the carb until that stops while the plane is flying. See my post above.
You can change the plug all you want, but if the carb high speed needle is set to rich, you are going to continue to have problems no matter which spark plug you use. Which plug does the engine come with from Zenoah? I do believe the 38 uses the RCJ8 plug, not the 7.
Good luck! Please post the results of your test. It will be interesting to see what difference the plug does make.

Flypaper 2

Fighterpilot is right about the mixture being possibly to rich. fly it without the cowl till you get it dialed in. Use the pinch test. Run it full throttle and pinch the fuel line. It should gain a few 100 rpm before slowing down. You should gain a few 100 rpm in the air as it unloads. Also try putting the hole in the plate facing the back. When the mixture is right the plug centre electrode should be burning a tan brown colour. Just be carefull and make sure it is tied down. Let us know how you make out.

Panzlflyer

My Feedback: (15)

Im having the same problems with a G62 after I changed to the Easy Link setup. The carb on my Stinger is exposed and the only way to mount the thing is with the hole on the outside facing forward.
Fist it was to Rich..We leaned it and now Im into the Deadsticking routine. Finally didnt make it back to the runway after the 5th deadstick.
Only happens on a downline. Runs fine on the ground and ran fine before the easy link.
Holes/gaskets etc/fuel lines all check out okay
Im curious

AtomHeartMother

Some people have had success with soldering a piece of brass tubing over the diaphragm hole. Then they'd run a piece of fuel line from that tubing, into the fuselage. The idea being to better equalize pressure for the diaphragm to meter fuel to the engine.
As mentioned before, playing with a velocity stack is always worth a try as well.
One other thing might be to take a good look at what prop you're using. If it's really rich and you can't seem to tune it out, maybe it's not enough prop for the engine. Alot of motors will 4 stroke and run rich without enough load on them. Could try a slightly larger diameter and/or pitch to load up the motor a little more.
Tuning the engine to a super lean condition for a desired performance in the air will only shorten the engines life.

Fighterpilot

My Feedback: (2)

I have run 3 Zenoah 62's, 3 - 23's, and have never had anything but satisfaction from those engines. On the G-62 I run a Zinger 20 X 8/14. On the 23's I run 15 x 8's. On G-38's my friends are running 18 x 10's.
Again, if the engine is too rich when only in the air, with the carb hanging outside of the cowl, you should be able to lean it out just enough to get a consistant and lean enough run to stop the gurgling sound (like it is four stroking) Don't lean it out half a turn, the needles are very sensitive, I'm talking about 1/8 turn at a time until the engine runs smooth in the aircraft. I am assuming that all other things have been checked in you fuel plumbing system to insure there are no leaks or restrictions of the pick up or vent lines. If the engine runs good on the ground, in the airplane, there is no reason why it will not run good in the air, while in the same airplane. When the air passes over the carb ventura while flying, it causes the engine to go rich. Air is being sucked out of the carb opening causing the engine to go rich. Try leaning the engine out 1/8 turn at a time, until you get a good consistent run while flying without the engine going rich. We have had a Quadra 52, US 41, and a 4.2 Sachs all do the same thing when the carb is mounted outside of the cowl and the engine is adjusted for a static run on the ground, and then put in the air and flown. They have all gone slightly rich needing anywhere from 1/8 to 1/2 turn in on the high end needle valve.
We've beaten this to death, so let us know how your engine runs the next time you go out and if you followed these instructions.
Once again, good luck
Bill Krummel

Panzlflyer

My Feedback: (15)

Update.
I finally put a Flap/spoiler over the hole in the diaphragm using 2 of the cover plate screws and retried the whole thing.
DIFFERENT beast!!!! ran just fine up down and sideways.
Also got smoother idle and transition.

dxrx

My Feedback: (134)

Andy
Do you have the pictures of your set up
I have the same problem with my G38 and would appreciate the help
Alan

Nogyro

My Feedback: (10)

[QUOTE]Originally posted by AndyT
[B]Im having the same problems with a G62 after I changed to the Easy Link setup.

Guys I tried the Easy Link setup on my G-62/ Giant Stinger combo after 50 hours of perfect running from my old set up. I always had perfect transition and NO richness on my old set up which was a B&B bellcrank & velocity stack. I never got the engine to run right with the easy link setup. After you rotate the carb, that puts the whole in the center of the diaphram cover facing foward. I tried the brass tube bent around to the inside of the carb venturi, I tried putting a piece of tubing on the brass tube and running it inside the fuselage. I rotated my velocity stack,no good. Nothing worked. Finally I took the da_ _ thing off, put a new B&B bellcrank set up back on, reset the carb to original settings, and flew with confidence again. I now have 87 logged hours on the engine/plane with never a dead stick. Toss the the Easy Link carb isolator in the trash where it belongs before it costs you $1000 in a crash! I'm glad I did. My $.02 worth.

Panzlflyer

My Feedback: (15)

Did you replace the insulator gasket.
The fist time round I didnt. As I removed it all to try to figure out what was up I decided to replace the old gasket as well as add the spoiler. Im not sure if that also contributed to the problem.
I will post a pic soon.

Panzlflyer

My Feedback: (15)

Alan hope this helps
Used aluminum flashing

Panzlflyer

My Feedback: (15)

Note to the above...
A dab of shoo goo stops any vibration although ataching a flat piece to a round surface holds it steady and although the pics cant show it the hole is completely unobstructed

Fighterpilot

My Feedback: (2)

I see you have the opening on the velocity stack towards the rear of the engine. I've always seen them installed with the opening facing the front of the aircraft, thereby forcing air in the carb. With it facing rearward, like shown in the picture, it tends to make the engine run richer while not forcing as much air into the carb ventura.
Could be wrong, but I've always seen it facing the other way.

Panzlflyer

My Feedback: (15)

In reality the stack is vertically alinged.
It ran fine that way before the Easy link so I refitted it the same way.
After canvassing numerous opinions I was told that it was undesirable to "ram air" the carb more to smooth the air flow and prevent blow back.
Open to suggestions although Im loath to mess with it again

dxrx

My Feedback: (134)

Andy
Thanks for the picture of the set up
I will try it
Regards
Alan

Panzlflyer

My Feedback: (15)

Alan
flew my trouble again yesteday...1/2 gallon of gas and no problems. Alittle burbly at midrange but I can now throttle back and dive with no cutouts so Im quite happy with the fix.
Still not sure if it was the isolator gasket or the hole although judging by the condition of the old gasket Id say it was the orientation of the hole.
The idle rpm has definately improved.

dxrx

My Feedback: (134)

Worked on it tonite
I will try it this week end and will let you know
Thanks for the tip
Alan

davo74

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Alot of goo on the plug could mean too much oil in the gas mix too...

dxrx

My Feedback: (134)

Finally the weather cooperate enough to have a couple of flights
It does improve the bubling some but did not get it cure completely I gess my set up still cause some turbulences at the area ........
Thanks