RunRyder - The new 643 carb is on board my heli. What are your thoughts, here's mine...

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Gasser Model RC Helicopters > The new 643 carb is on board my heli. What are your thoughts, here's mine...

rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

I swapped out the trusty old 167a carb for the new 643 carb last night. Went out in the blustery mid winter weather (wind, 39 degrees and cloudy) this afternoon anxious to try it out. Here is what I found:

1. Engine does seem to run smoother around mid-range, less kicking and practically the low speed needle seems to make no effect. In other words, the engine is not talking to me like it used to. I can open and close this needle like 1/8th turn and engine runs practically the same, though on leaner setting it seems to race even though on a gv-1, and on richer setting it seems to run closer to the gv-1 preset rotor speed. I'm actually surprised that it doesn't maintain the lower head speed when on the leaner setting. I thought the gv-1 would throttle back. Anyway...

2. Muffler seems to smoke. On the old carb, there was no smoke and if I got it to smoke it was kicking all the time. With this carb it smokes on the 1 turn out, and its a smoker on the 1 1/4 turns out on low. No kick really but maybe a hint of one towards the richer setting. As the engine heats up, the smoke does get less, but on cold takeoff, I thought it was a nitro ship! Didn't do that with the old 167a carb.

3. High speed I set it to 1 1/4. Full power climbouts and I see NO POWER increase. Seems to behave the same like the old carb. I can get it to climb wide open and maintain rpms, and when I pull back on the cyclic to loop it with power, it bogs down. I was expecting to see less or no bog if there was a power increase, I don't see any difference -- at least that was my way of testing the power. Maybe there is more power, but I just don't see it.

4. On a bad note, I rolled it to inverted and the engine gasped for fuel it seemed, almost quit and recovered. Yikes, what was that? I tried several loops and noticed it was doing it off and on. I tried to richen the needles and it seemed to get better, but then it also seemed to get too rich and lose power. Then I tried to lean them a bit (leanest I went was 1 turn low and 1 1/8 high) and it quit when I went inverted. At this time I was expecting it and at 150 feet up it was easy to flip to upright and auto in. Unsolved mystery.

When I got home I thought maybe the silicone rtv sealer I put down blocked the carb pumping hole. Took the carb off and checked, there was some silicone there but the hole was not blocked by any means. Picked it out with the tweesers and put the carb back on. I guess I need another day at the field fiddling to figure out these needle settings and hopefully get it to run like a top inverted or upright.

Any of you guys have use feedback on this? Let me know if I need to be looking for something, otherwise its back to the field and hopefully a little warmer this time around. Bottom line is that it was smoother at hover, was not picky at all where the low speed was (so now how do I determine what is right?) and no additional power observed. As always, I'm using Yamalube R2 at 30 to 1 mixture.

-=>Raja.

1005 Xcell Gas, BHH G26 3D Plus, Jewel Generator
Spectra-g, BHH G26 3D Plus, Jewel Generator

10-24-2003 Over year old.

gyan
Key Veteran
Location: Surrey, BC Canada

I'm very interested in your analysis as I' m considering the WT 643 upgrade myself. Let us know what you've found out. & Thanks

10-25-2003 Over year old.

rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

Carb update

Ok:

Went out today and flew this carb again. Here is what I found:

Same problem with the cutouts while inverted. Actually, usual heli gang in the background commented: "time for new underwear..." I knew it was coming, so no problem there and I just landed and richened the idle up some more.

The more I richened the idle, the better the gv-1 maintained the low speed in normal mode. Otherwise it was running faster than requested. Since it was cutting out in inverted and coming back, I figured lets richen and it will fix both problems. I ended up with the low somewhere around 1 1/4 turns out. The cutout problem seemed to subside, so good thing there.

Then I tried power climbouts and in idle up 2 it was blubbering a little so I richened the high needle to something like 1 3/8 from 1 1/4. Blubbering went away and engine seemed to pull steady at full collective in all flight modes. Someone had a tach and we registered about 1710 rpms at idle up 2 full power climbout. This is BETERR than what I used to get as in idle up 2. I had the top pitch idle up 2 at 90% (all others on 100%) and today I made it 100%. That being the case, the engine seems to pull 1700 rpms on 100% or say 1/2 degree maybe 1 degree more (I have to measure it) and maintain the same rpms. This mean some more power is apparent. A good thing!

Lastly, with more power comes more gas, and I noticed that after the usual 15 minute flight my 10oz dubro tank is about 1/2 way between the bottom and the top of the hump in the tank. (hump means larger area on the bottom of the tank). With the old carb, it used to be at about the top of the hump after 15 minutes. So I would guess I'm burning an extra 15% of fuel, and perhaps in turn getting an extra 10% of power too.

As far as the smoothness, the old carb used to be pretty smooth for me. This one since I richened it so much it tends to kick a little in a hover. Not a big deal, but not picture perfect either. If I lean it then the gv-1 cant keep the engine at 1500 rpms in normal mode, and it tends to cut out in inverted which I don't quite get. If I richen it then gv-1 maintains rpms, and cutouts are practically (see next paragraph) gone though the hover is not perfectly smooth (minor kicking).

As far as the cutouts, after I got the needles perfected I did 3 flights. On the last flight after takeoff and on my first loop it cutout for a second and came back. After that it was fine though it did it... Not sure if it is sucking some air bubble from inside the carb or in the dubro filter that I have, but it seems to do it once and then its ok for the rest of the flight. I guess I can just expect it on the first loop and then go from there, unless someone has any suggestions on what to do.

Today's activities added 5 flights for a total of 1034...yeah baby!

Any questions, let me know. Any comments, feel free!

-=>Raja.

1005 Xcell Gas, BHH G26 3D Plus, Jewel Generator
Spectra-g, BHH G26 3D Plus, Jewel Generator

10-25-2003 Over year old.

Chris Bergen
Key Veteran
Location: location

Engine cutting out

Hey Raja,

If I don't let the engine get good and warm before doing aerobatics, I tend to see the same thing on the first flight.

Normally I'll hover around a bit, to get rid of the first flight jitters, and let the engine warm up, then go up and do some lazy loops and rolls. Once I am sure the engine is warmed up, I'll start getting a little more aggressive. This especially holds true with cooler weather coming in.

Speaking of cooler weather, You'll also notice a power increase, both from the engine and in the efficiency of the blades.

Have fun and don't be such a stranger!!!

Chris Bergen

10-26-2003 Over year old.

ImRich
Veteran
Location: Derry, NH USA

Raja,

As you know I have this carb on my new engine.

I removed that in line filter I was using and my engine burp (one short out out on negative G manuvers) went away.

Look to your plumbing for this cut out issue.

I filter my fuel going into my tank, so I guess there is no need for my paranoia and triple filtering. (I'm using a felt type tank pickup filter/clunk).

There must be a bit of air getting into your line and that is why the engine is burping. Sometimes it's the simple things!

I haven't been flying much lately, between the weather and fixing up the house a bit.

---
Rich

10-27-2003 Over year old.

HOMEPAGE

rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

Filter

Yeah I suspect it can be a bubble in the filter. I toyed with the idea of removing it, but then again even though I filter my fuel into the tank from the can, every time I go to clean out that filter there is stuff in it. And, there is stuff in the carb itself on the internal screen. The way I see it is that the external filter adds surface area and slows down the clogging of the internal screen. If I take it out then some dirt from somewhere will get in there and eventually block the internal screen.

-=>Raja.

1005 Xcell Gas, BHH G26 3D Plus, Jewel Generator
Spectra-g, BHH G26 3D Plus, Jewel Generator

10-27-2003 Over year old.

ImRich
Veteran
Location: Derry, NH USA

Wow.. if you filter into your tank and still get crap.. look for better filters!!

Look in my gallery, you can see a picture of the felt clunk filter I'm using now, it's the one on the left:

. If any dirt gets past this thing, you have bigger issues and you should investigate them right away!!

Do you remember the extra filter I had between my tank and my carb?
You can see it in this picture:

I removed that and all my engine burbs went away.

Click on these pictures for a larger view.

Now I filter as I fill my tank. And the felt clunk filter will take care of anything that I miss.

---
Rich

10-27-2003 Over year old.

HOMEPAGE

torque
Senior Heliman
Location: west virginia

rbort

i use to have the same prob with my xcell as you are having.
if, i would do a loop the engine would almost cut out. so what i
did was on start up, i let the engine warm up and while at an
idle, i would pick the helicopter up and invert it. i could hear a
change in rpms. then set the helicopter back down and go fly. i
never did find what was causing the sag in the engine.

10-28-2003 Over year old.

Dr. Fibinotchi
Key Veteran
Location: Sioux Falls SD

That happened with me

I have noticed also if I just do some figure eights or low end stuff I could feel and sometimes hear the rpm increasing toward the end of two minutes of hovering. I redid my throttle curve which now flies more like a gov, but I cannot still give it full stick without it coughing. Does this mean too rich/ lean or is my servo giving it too much and you cant go 100% mechanical?

Also I did have mine cough coming in inverted too sometimes. I was running a filter and will take it off. Nothing like a few inverted suprises to clean our your shorts...hehe

-Cody

10-28-2003 Over year old.

rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

Clearing out the filter instead of your shorts

What I do now is move the filter up and down and tilt it while I pump the carburator before starting the engine. If there is any air in there it helps to get it out of there.

Also, I just take off, go right to idle up one and fly up and away to 150 feet altitude and do the first loop coming towards me in a good position. Generally speaking if I jiggled the filter while pumping the carb chances are it won't stall for a second while I do that first loop. And, if it does I am expecting it, in a good position in case it quits, and once I'm through it then I am good for the rest of the flight.

Beats changing the shorts out!

-=>Raja.

1005 Xcell Gas, BHH G26 3D Plus, Jewel Generator
Spectra-g, BHH G26 3D Plus, Jewel Generator

10-28-2003 Over year old.

Billme
Key Veteran
Location: MS

Having a throttle servo to fast, willl cause the cough also....If your not above a hundred % on ATV's it might be a problem for aerobatics...
I'm going to have to raise mine up some more on the Predator gasser myself....I'm 100% right now, and will move it up to whatever the next hole demands on the servo arm...

What happens is the engine will think it has no load on it momentarily because of the fast throttle servo with quick movements that swashplate to throttle mixing has sometimes...
When you have the fuel system corrected, and your still having the problem, then try the above..
Best Regards,
Bill

10-28-2003 Over year old.

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Gasser Model RC Helicopters > The new 643 carb is on board my heli. What are your thoughts, here's mine...

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