buzzard bait

I have an Enya 53 four stroke with the older "air bleed" carb (someone said it's more sophisticated than an ordinary air bleed). I've been running it on the test stand with an APC 12x5 prop. It peaks at about 10,800 - 10,900 on 10% nitro, synth/castor blend. My problem is that as I throttle it down, rpms become unsteady around 4000 rpm and it quits when I try to get down to 3000. The best I've gotten is erratic running from 3300 to 2900...if I try to go a hair below that it quits.

Here's more:
1) put in new Enya #3 glow plug...no change
2) fuel is fine...runs other engines well, it's not old
3) fuel tubing over needle valve
4) blasted compressed air through carb...everything seems clear
5) tried many settings of air bleed...best setting was with the bleed hole almost closed! At that point, pinch test on low speed would give a momentary rpm bump before quitting. When I opened up the hole, the engine would die on low speed even quicker.

So, if the bleed hole is almost closed and it still runs, could these symptoms be caused by an air leak somewhere? If so, how would I find it?

Thanks,
Jim

Hobbsy

My Feedback: (102)

Jim, if all else is well in the carb the airbleed screw should be very near the center of the hole. Is this carb one that you can pull the carb barrel out to the right to choke it, if so, is it all the way back to the left. I have the .46MKII version of your engine. If I tried to run a 12x6 on the .46 it would have a very fat midrange, when I ran an 11x6 or a 12x5 and let it rev to the high 9s it could be run leaner and not more fat midrange. Do you have a 12x6 by any chance. A 12x6 is perfect for my .53TN.

gkamysz

My Feedback: (19)

The intake manifold has two seals. A piece of large diameter silicone tubing in the head and an O-ring in the carb base. Make sure the manifold is pushed into the head as far as it will go. I would also suggest checking your valve clearance.

Taurus Flyer

buzzard,
I am interested in the exhaust system you use,
see pictures of the 60 4C maybe comparable.
Is it like picture 1 or 2?
If it is like picture 1, do you use the exhaust pressure connection? If you do, try without.

Cees

buzzard bait

Forgot to mention that I adjusted the valves.

I haven't taken the carb off yet. The seals look good, everything feels snug, but maybe those seals start to leak when they get old?

I know a 12x6 is the more common prop, but I don't think a little more load is going to solve the problem. I had the same problems running a Rev-Up 12x5, which gave it more load than the APC. I was hoping the mass of the APC would smooth out the idle, but it made no difference. There doesn't seem to be a choke feature on this carb.

Yes, having to almost close the air bleed seems to me a sign that something is wrong with the carb or its connection to the engine

Jim

gkamysz

My Feedback: (19)

Oh yes good point. No muffler pressure required.

To choke, pull the barrel out. I happen to have a carb on the desk.

Hobbsy

My Feedback: (102)

It won't pull out easily if its been a while or never.

noveldoc

My Feedback: (2)

Ran an old OS 52 4 stroke on a 12 by 8 prop. Pretty pitiful and erratic. Switched to a 12 by 6 and it runs great.

Could be your problem.

Tom

gkamysz

My Feedback: (19)

He's getting almost 11k in the Enya .53. That's right about where it should be.

Pippin

I use APC 11x6 and 11x7 together with 1%-5% nitro only, peaks at 11.000rpm with the 11x6, idles down to 2.500rpm. But mine is the newer version with black valve cover. You might get the newer carburettor to improve handling.

buzzard bait

I'm sure the newer carb is better, but there is no way this thing should fail to idle consistently under 3000 on a 12x5 prop with the old style carb. Something is wrong, even though the engine overall is in good shape and makes good power. I just can't figure out the next move. Seems to me I've read about putting something on the joints that will reveal a leak when the engine is running. Anyone know about this?

Jim

Taurus Flyer

Jim,

If you don't use exhaust pressure my next suggestion is, valve timing oké?

Cees

buzzard bait

Greg and Dave, I see I missed a couple of posts. The picture of the carb is very helpful. That is exactly what mine looks like. I was able to pull it out, but not as much as Greg shows on his. What keeps this from moving around while the engine is running? There doesn't seem to be any spring action.

Jim

buzzard bait

I am using muffler pressure.

I did adjust the valves, but if you mean the cams, then that would affect top end power, wouldn't it?

Jim

gkamysz

My Feedback: (19)

In the photo the socket head screw to the right of the throat is a ball spring detent mechanism. The idle stop screw on the back side also limits the outward movement of the barrel.

I'd pull the carb and check the seals on either end of the manifold.

Taurus Flyer

Jim,

Don't use muffler pressure.
The carb sucks 25 % of time fuel the other 75 % of time the muffler pressure will load the space before the closed inlet valve with fuel blowing down the glow plug after the valve opens.
The timing of the cams can be wrong when someone did work on it. If you want to check this give me a sign, but first try running without muffler pressure is important.

Picture, low idle inverted without an on-board glower, no muffler pressure.

Cees,

gkamysz

My Feedback: (19)

I think valve timing is OK for the power output you're getting. Try it without muffler pressure as suggested. I used an OS muffler on installation of my first 46-4C and absentmindedly connected the muffler nipple to the tank. I could not get it tuned correctly. Realizing the stock Enya muffler had no pressure fitting on the muffler, I disconnected it and it ran great.

buzzard bait

OK, I'm going to pull the carb and check the seals. After that I'll try again and if it doesn't work, I'll try without muffler pressure.

My old Saito 40 only has an exhaust pipe, but it has a nipple that appears to be for a tank line. If I hook that up, the engine runs very strong for a few seconds and then quits. No needle setting will keep it running. But if I take off the pressure line it runs fine, for awhile. But after half a tank or so, it leans out and quits. Without muffler pressure, the difference between a full tank and a quarter tank is way too much for it.

I'd rather have the muffler pressure because of that. The Enya comes with a muffler with a nipple.

I'll post results. Thanks for all the input.

Jim

gkamysz

My Feedback: (19)

I dug out a 53-4C I have and it does have a pressure fitting on the muffler. I can't say it's factory issue as it appears to be epoxied in. I have the manual available here if you don't have a copy, www.dieselrc.com/download.html .

Taurus Flyer

Jim,

To show you how a muffler tap looks like without a hose.
Good luck with your engine.

Cees

buzzard bait

Greg, thanks for the link to the manual. There was an interesting note about setting it up: "Usually it is not necessary to pressurize the muffler." So that's their own advice.

I took off the carb. The seals seem OK, but how would I know for sure? It would be nice to be able to replace them. The carb has some interesting little holes in it that I don't understand. I used my air hose to blow them out in case something was clogging them.

Cees, I didn't doubt that you had nothing attached to it. It is interesting that it is different from mine, which has the nipple screwed into the muffler body.

Jim

Taurus Flyer

Jim,

I was wondered you did not give me an answer on post 4
I did have to ask you twice if you did use muffler pressure.
Now you are going to take the engine apart first?
Don't you believe me it not the best way to combine a bleed air carb with muffler pressure?

Cees

buzzard bait

When the manufacturer supplies a nipple on the muffler, as in this case, I always use it, and I've always assumed other people do too. That's on at least a dozen different engines that have air bleed carbs, not counting many others in my club. It always worked. As I explained above, my Saito without muffler pressure will not run out a tank without leaning out as the tank gets low. So, as I said above, I would prefer to use muffler pressure, and I don't understand why it won't work. Why would a company like Enya put a devise on their engine that will cause it not to work?

I took off the carb to clean and check seals because if the engine does not work using the equipment provided by the manufacturer, something has to be wrong. Especially when the best idle is with the air bleed almost completely closed. That suggests to me a leak somewhere.

Cees, I'm not intending any disrespect, but we all have our own experiences, and when you post here you get a variety of advise to weigh, and then you choose based on what fits your experience, right?

If the engine will only work without muffler pressure, then I'll just live with it. But then the question will be, how well does the mixture do when the tank runs low? Does it lean out? I guess yours must not because you're happy with it.

Thanks for weighing in...I will definitely try it without pressure and let you all know how it goes.

Jim

Taurus Flyer

Jim,

My problem was, I did not get an answer on post 4.
I think biggest problem is, you USA members did forget Ed Kazmirski became national and world champion pattern flying with engines feed by bleed air carburetors.
My opinion is, what munufacturers supplies do ask for one thing, change!!
Let me hear what your results are, and have fun!!!

Cees

Hobbsy

My Feedback: (102)

Greg, my .53 TN has a pressure tap on the muffler also.