Japanman

Hi,
I just stripped down my AME cl engine to which I fitted my airbleeding norvel carb. it is smooth bore with a venturi of 3.4mm

I used a tapered sheet metal reamer to take out the horrible step that is in the stock carb at the barrel, and again from the back of the carb to make sure the top and bottom holes are the same size. this done, the barrel tapers to the smallest point in the centre- right where the fuel outlet is.

Now the air bleed notch will have much less effect amd the carb will be too rich at idle- so to fix this I put in a 1.2mm air bleed hole that angles up diagonally from the back of the carb to just inside under the notch used as an air bleed in the carb body. I drilled this by hand using a pin vice making sure that the hole intersected the throttle stop screw so that it becomes the air bleed mixture adjustment.

Because i greatly dislike the needle hanging of the tiny barrel, I moved it to the other side where I used the N.V body from the CL carb as the main meat for the new valve unit.

Seems to work well, and is not so sensitive to attitude- which I think is in part caused by the weight of the stock needle loading the barrel and exaggerating the barrel to carb body clearance, causing airleaks.

J.M

rrragmanliam

My Feedback: (1)

Nice work JM. Have you actualy run the thing and what were the results? If so what would you do different on the next one? Do you think these modifications would work with the Big Mig porting? A stock Norvel idles ok if all is right but it's nothing to write home about. A functional air bleed is all these motors are missing. I'm going to have to try it. Great pics!

Thanks,

Rrragman

Japanman

I works fine with big mig porting- I was running it on a bigmig engine before switching it to the ame.
you might like to put in a small spraybar for running 6/3 props if you don`t run exhaust pressure. I had to go to 3 turns with the needle without pressure, which I think is a bit much.
with muffler pressure even with the APC 6 by 4 E prop (whoops, let the cat out of the bag) I never had to run above 3 turns-
The idle is very good I`d guess it is something like 3 or 4000 but it is hard to know with no tacho- but very very low anyway. It transitions well too, no hesitation on 15% nitro fuel.

J.M

rrragmanliam

My Feedback: (1)

JM, You are absolutly right here, on one of my .061 motors this is a big problem. Whenever I touch the needle the whole assembly rocks back and forth a little and you can instantly discern an rpm change caused by the air leak. Then to exaserbate the whole situation the carb mounting bolt hole was drilled a little off so that the carb didn't seat properly. I used a bigger o ring at the carb/case interface but still need to address the wobbly needle assembly.

Darren

Japanman

Hi Darren
On my first norvel the throttling got progresivly worse as the engine vibration made the needle valve assembly wobble and wear away at the barrel.
I think it was really a problem because the barrel to carb body fit was too loose to start with, so that it could move around.

As the idle was too lean for my prop/fuel/tank setup to start with when I got my next norvel I decided to have a look to see if there was anything I could do about it- hence this and other solutions. ( I converted the other one to a twin needle type carb)

J.M

rrragmanliam

My Feedback: (1)

Yes, It's the same problem I refered to eariler. It's a shame one has to investigate and repair these MFG isues. Norvell engines are inexpensive and by far the biggest bang for the buck in 1/2A, so I guess I can't complain too mutch. It sure is a hassle when you get one out of the box that needs modification to get it to run right. As far as the throttle barrel to carb case fit goes another simple fix would be for Norvel to machine a grove in the barrel and put in a small o-ring to seal the case to barrel gap. If I could do it myself I would. Today I wound up putting thin slice of 5/32 ID fuel tubing (about 1/32") between the carb case and the throttle lever. I did away with the needle clicker and, used fuel tubing to seal the gap at the needle and provide friction to prevent it from rotating once it was set. Now it runs great but what a hassle!

Darren

Japanman

Nice fix.
I`d also say that norvel are great for bang for your buck. Looking at the carb setup I can see it is a genius bit of simplification, to reduce the number of machining operations. I wonder if the position of the fuel nipple and needlevalve could be reversed in manufacture?- I suspect this would stop the hassels we`ve had.

J.M