Nogyro

My Feedback: (10)

I've been battling these DA50's for 6 mths. Between the rod and crank replacements and the new pulse line mod. it's driving me crazy. I know how to adjust carbs, and I've been chasing the needles on these continuously. Get it set just right, then the next day it's either rich in midrange or lean and won't start. [:@] We finally crank my buddies DA50 for the first time today, and it's a different animal than mine. We set his needles like mine, and it was so rich, top end was only 5500. That really got me thinking. My high needle has been at 2 1/2 turns. It sounds pretty well peaked out in the air, but not sagging on long full throttle up lines. I opened my HS needle to 4 turns, and no difference. It's peaked out at 1 1/2 turns out or 4 turns. I CAN NOT get it rich. You should be able to peak one at say 7,000 and drop it to 6500 with the HS needle, I can't. Got two to the DA50's and they are both the same.

I pulled the needles to see it they were in backwards and they were not. Physically can't do it, different thread size. Blew the ports out, screen is clean, even pulled the line off the fuel tank and stuck it in my gallon jug, no difference..........

Can I go in and bend the lever arm in the carb to allow more fuel through?????

I'll be calling DA in the morning to see what they say. I got a hunch I'm not the only one out there with carbs like this, and this may explain the rod bearing problem.......running to lean......

TIA

H. Wayne S

My Feedback: (18)

If you cannot get a rich condition on the high side at WOT, it is usually a sign of fuel starvation. You do not have a large enough fuel line from and in the tank. Make sure you use large fuel lines and drill out the clunk.
Just my .02.

Nogyro

My Feedback: (10)

Running 3/32" tygon tubing. Took the line off the tank with no clunk on it and stuck it right in my fuel jug and it made no difference. My buddy is running the same fuel line as me and his gets plenty rich. A lot of guys even use 1/16" on larger gas engines than a 50 cc's and get by with it.............

Jemo

My Feedback: (5)

You sure don't need larger lines, as I am sure you know. Do you have an in line filter ??. I had a similar problem once and that was the cause, also any kink etc, etc, . You know what I mean.

Nogyro

My Feedback: (10)

Chain saw felt filter in the tank, no kinks. I took the line off the tank, stuck it in my fuel jug with no filter on it.....straight shot to the carb.....no difference.....

Pulled carb off this morning and checked fuel arm level.............it's at specs

Shot WD40 thru ports and everything appears clear.......

No difference in WOT rpm with HS needle at 1 1/2 or 4 turns out.....this has really got me baffled.

Calling DA now.

famousdave

My Feedback: (61)

The filter probably won't make any diff, but most of us filter the gas before it goes in the tank and don't filter the on-board gas as it weakens the pulse from the carb. I doub't that is your problem, but it could be.

DP

David_Moen

I don't like in-tank filters either. If you have a filter on the fill line of your fuel jug you are doing the same thing. There is also a filter screen in the carb that is much easier to service than pulling a fuel tank apart.

DMcQuinn

My Feedback: (13)

Disconnect the fuel line at the carb and hold it a few inches below the tank. let the fuel siphon freely into a jar and measure the flow rate. I believe it should flow at a rate similar to what the engine demands at full throttle - probably around an ounce per minute. If the pumper portion of the carb is working, it should be able to deliver at least as much as this siphon test. So if the siphon test is OK, then I would think your felt clunk and fuel tubing are OK. The pump could be weak. In this case you replace the diaphragm of the pumper side of the carb. I had a similar issue and found that my tubing line from the regulator side of the carb into the fuselage was melted shut. completely closed off where it passed by the muffler. I was running a line from the atmospheric reference side of the regulator into the fuselage in order to minimize surging due to changing cowl pressure. Most carbs do not have this line.

Nogyro

My Feedback: (10)

Thanks for all the suggestions. I talked to Brian at DA this afternoon and explained the situation. He informed me that they can't even get the DA50 to get rich at full throttle. They peak it and fly it there. He was very surprised that my buddies 50 could be dropped almost a 1000 rpm on the rich side at WOT. My question is if you can't go on past peak to 200 rpm or so on the rich side, how do you ever KNOW what peak rpm is?? I've NEVER seen a chain saw, leaf blow, or weed whacker that couldn't be richened up that much. Most of the time you can get it so rich it will almost die on you. They're sending me a new carb 2 day delivery, so I'll get it on Wednesday. Curious to see what it does. Brian said the QC on the carbs is awful. They have a pile of them up there that are just junk.

I tore into the carb again today for a 2nd time and really went through the low and high ports. Got to figure it out anyways. This carb has 3 ports on the low needle, and one large one for the high. Thing is, the low needle has a larger diameter tapered needle than the high. Seems to me you would want it the other way around.

I assume the fuel flow works on vacuum thru the venturi. On that assumption, any leakage around the needles would prevent maximum fuel being pulled thru the ports. I had a chain saw once that kept going lean on me, and it had a bad O-Ring on a needle, so I wraped teflon tape around both needles, and the engine responded to tuning much better. It held idle without fluctuating, and I was actually able to get 50 rpm on the rich side at WOT. One other thing I found out. There is a spot at 4,000 rpm that will be lean if you set the low needle for best idle and transition, and you can't get it out with the high needle, it has to be the low. I had to open the low 1/4 turn to solve that issue, then of coarse it is rich at idle. I've noticed this spot before, because that's the rpm I seem to want to do my harriers at. Not a good time to be lean. If you were able to be 200 rpm on the rich side, it might catch that spot at 4,000 on the high needle instead of the low.

I'd be curious to know from you guys that are running DA50's, how many of you can adjust the high needle 200-300 rpm's on the rich side?

Josey Wales

My Feedback: (61)

I just adjusted mine tonight..I have a Menz 22-8 and I peaked at 7300 rpms turned the high needle out about 1/8 turn and rpms dropped to 7200..Turned my low needle about 1/16 out and drpped to 7000..Im still breakin in on 32:1 DA says the high end really isnt efective at all..I spoke to Brian and he said the low end affects from idle to 85% rpms..I know one thing on the ground it runs like its overly rich..sputters and idles rough..once in the air after a few laps it warms up and is as smooth as can be...I can go from full idle up to full power with just a slight burble in the midrange..so far its running great for me knock on wood..

H. Wayne S

My Feedback: (18)

I'm sorry, but there is something seriously wrong here. You should be able to richen up any and I do mean any engine on the high end at WOT to a point it will at least drop 25% of its peak rpms. I cannot believe a company like DA would say they cannot get one to go rich and still sell the thing.
I don't buy this and now I won't buy that.
Just my .02.

Nogyro

My Feedback: (10)

I've got to tell you, that's the way I see it also. Mine is turning a Bolly 22 x 10 wood prop at 6600 peak on the ground. The richest I can get it is 6550 with the high needle. Sure, I can go in and open the low and drop it another 50 or 100, but then that screws up the idle. As it is you have to have the low 1/4 on the rich side to take care of the lean spot at 4,000. Now throw into the mix, as the temperature changes on the engine in the air, the low and midrange mixture change..... The needles don't move, but the way the engine runs does. I don't expect it to stay perfect 100% of the time, no matter what throttle setting or attitude you're in, but when it makes as drastic a difference as it does, this is unacceptable in my book....my style of flying...IMAC/3D.

I'll be watching real close as my buddies DA50 breaks in. His DID richen up 25% at WOT with the high needle. Brian said he would sure like to have that one back in shop to take a look at.

Antique

My Feedback: (4)

Bottom line..[8D]...The carb on a DA 50 was originally made for something else, probably a chainsaw...The manufacturer of the chainsaw had the carb metering holes calibrated for that particular engine...Apparently the hole in the carb that is controlled by the high speed needle is just large enough for that rpm and no larger, no matter how far the needle is screwed out....That's apparent by having to adjust the carb to 85% of the top rpm by using the low speed needle..It was not designed to be that way....I guarantee I could make the hole large enough to flow more fuel and richen up the mixture...I also think a WT499 from a Glow G23 would do just that, it has large enough fuel passages to flow at least twice the amount of gasoline needed for the G26, so much so that it also works with methanol with no other changes...

Nogyro

My Feedback: (10)

Ralph, you don't know how hard I had to bit my tongue to keep from mentioning your name to Brian when he said they had sent some of the bad carbs out to some "carb specialist" and they couldn't do anything with them. I even thought about drilling out the seat on the high side a .001 inch, but was afraid the needle taper would be too small then.

canavanbob

My Feedback: (20)

This sounds like a design problem, not a carb quality control problem. No amount of quality control is going to make a carb that is not suited to the engine perform any better. I think DA just picked the wrong carb for the application. Just send it in, I'm sure they will give you a new carb within a week.LOL I think I will wait a year or two before I get a DA 50.

Bob

Antique

My Feedback: (4)

I know that a carb can be made to flow enough fuel because
we convert gas carbs to run methanol in our Giant Scale race planes..Mostly Zenoah GT80s, although the same thing works for all carbs..We drill out the inlet needle hole to .083...The 3 small holes in the venturi under the welch plug are drilled out to twice the area, and the high and low needle holes are drilled out larger, just enough so that the taper on the needle still closes off the holes when screwed all the way in..If the needle doesn't have a constant taper it can be ground just enough to make it right...ANY carb can be modified this way, and if it will flow twice as much methanol as gas it will surely get rich enough with gas, probably way too much to even work....The WT499 just happens to be calibrated to work either way....Some carbs might have too small a hole in the brass high speed nozzle, but not likely...
A WJ64 carb from a GT80 modified this way flows enough methanol to let the engine run 11,500 rpm with a 19x18 race prop....
I have not tried it, but a WT76A from a 3.2 Sachs should be enough carb for ANY 50cc engine....It works very well on a G62..[8D]

Nogyro

My Feedback: (10)

Ralph,

The carb on my DA50 is a WT 436. What's that tell you?

And yes, I'll get my new carb from DA tomorrow, but I ASSUME it will be the same model that I already have.

What gets me is, if they knew they were border line on the carb to begin with, why didn't they experiment with a different one before putting these things into production?................

Antique

My Feedback: (4)

WT436, 7.94mm venturi, originally made for a Mac 65 trimmer...Looks kinda small, maybe they wanted good throttle response from the small bore ?
I don't have a book with the Mac 65 trimmer in it, don't know what size it was....

SAL98

My Feedback: (6)

I,m surprised no one has hit on your engine problem as of yet. Especially here on rcu, but anyways your problem sounds like it's with the float diaphragm lever that controls the needle and seat. It is not getting enough fuel at full throttle because the float diaphram needle is'nt opening up enough. The diaphram needle sits in the cavity right under the side plate with the hole in it. The diaphram itself which has a metal pin in the middle, pulses the lever and needle to control fuel flow. If the lever is pushed in to low then the needle will not rise enough to allow full fuel flow at WOT.

I had 3 ZDZ carb problems just like this and each one I had to adjust the diaphragm lever to get enough flow. Once this was done the High end needle went from 3 turns open to get a slightly rich setting to 1 1/2 open for a really rich setting.

There is a guy named Xipp on Flying cirkus that just explained (in a post) about the workings of a walbro carb. I think you will find this very useful
[link]http://www.flyingcirkus.com/forum/tm.aspx?m=51010[/link]

H. Wayne S

My Feedback: (18)

Never fails............................................. ............READ !!!!!!!

Nogyro

My Feedback: (10)

That was the first thing I checked, and according the specs, it's right on. Flush with the plate next to it...........

Any other idea's......[8D]

Antique

My Feedback: (4)

If the holes in the carb are too small in the first place no amount of lever bending will make any difference....

Nogyro

My Feedback: (10)

Well here's the plan. I'm supposed to get my new carb from DA today. If it doesn't give me satisfactory results,( I have my doubts) I'm going to buy a WT76A and slap on it and see what happens. If that carb is good enough for a G62, it's good enough for a DA!

AJF--2

My Feedback: (119)

I have been trying to find the prop size used and cannot. Did I miss it??? This can have an effect if it is on the strong side, but I am sure the folks at DA asked this also. (allow me to appoligize in advance if it is there and I just don't see it)

Nogyro

My Feedback: (10)

Running a Bolly wood 22 x 10, peak rpms are 6600, can only richen up to 6550. I've got a 22 x 8 Bolly(cut down 23 x 8) wood on my other DA50 and it turns up around 7,000. Haven't actually tached it.

I've tried a MenzS 22 x 10 on it, but it would only swing it at 6100, and the Bolly wood 23 x 8 was 6300.

We cranked my buddy's DA50 up for the first time with a MenzS 22 x 10, and we could richen it up to 5100, so the prop isn't the problem......