Nogyro

My Feedback: (10)

In my other thread, I installed a WT76 carb on my DA50 in order to get enough fuel at WOT to be on the rich side. This left me with the stock WT201 carb that was pretty much useless in my book.......So I took a chance and drilled out the high speed fuel passage and it worked just fine. For those of you that are having problems getting the DA50 rich enough at WOT, this will solve your problems. We did it on my buddies engine today and it worked great also.

First a word of caution. Some of the carbs are shipped with locktite on the high and low needles. Both mine were, but my buddies didn't have anything on them. IMO, sooner or later, this locktite gets down in the low speed jets and plugs them up. Nothing you can do to get it out either, trust me. [:@] If you start chasing the low side needle from rich to lean during a flight, chances are you've got some garbage floating around in there blocking 1 of the 3 jets on the low side. So the first step is:

1. Remove both needles and vaccum out threads in carb, then use wire brush in dremel and clean the threads of the needles.

2. Remove cover off carb( the one with the hole in it) and diaphrams. This will expose the needle and seat, and fuel ports to the needles.

3. I drilled out the high speed fuel passage going in thru where the high speed needle threads in, using small bits and a pen vise. I held the carb so the shavings would fall down out of the carb.

4. Start with a .035 bit, this will just clean up the original passage way, then go to .040, .043, then .046.

5. When finished, blow out passage ways both high and low with WD-40, then rinse with 2 stroke gas.(just as a precaution, don't know if WD 40 will harm the
diaphrams or the seals)

6. Reassemble carb, open high needle to 2 turns and low at 1 3/8. This should be real close on the low, and a tad rich on the high. I'm at 450' above sea
level, so your needle setting may vary due to elevation.

I know DA has been saying some engines have had rod failures, and some haven't. Those at high elevation would need less fuel, thus the stock carb may be just fine. For those of us at lower elevations, I'm thinking we're starving the engine on the top end thus running too lean causing rod and bearing failure....... I may be all wet on that assumption, but it sounds reasonable to me........All I know is my DA50 is a different beast with the carb mod, or changing to the WT76.

Scoubidou

My Feedback: (17)

I am tempted to do it for the 100RPM gain and i have to do the carb upgrade anyway to solve idle issue.

I'll let you know how it works for me.
Daniel

Scoubidou

My Feedback: (17)

They are very small bits?

Is it OK if i use only 2 bits?
1/32''=0.31
3/64''=0.46

Nogyro

My Feedback: (10)

I tried jumping 2 sizes and drilling by hand with the pen vise, it seemed like it was taking just a bit too much pressure to suit me. Just a little nervous on the first one if you know what I mean....... If you are careful you might be ok. Just make sure you stay centered in the passage when it first starts. Really it should center it's self. You might also want to double check your bits with a caliper to make sure they are what they say they are. This is the pen vise that I used. http://www2.towerhobbies.com/cgi-bin...&I=LXL466&P=ML

85bipe

My Feedback: (16)

I'm the second carb and you gain more than just 100 rpm. You can lean out the low needle so it won't load up and by being able to richen the high needle you get ride of the dead spot at mid throttle.The carb settings don't change in flight when the engine gets warmed up.Nogyro said it when he said it was a different beast.More tameI would go with the four bits. They are very small and are easy to break[X(][:@][&o]

85bipe

My Feedback: (16)

Guys be careful about the decimal point. The drill bits you need to use should be a numbered drill bit, Not a fraction. The drill bit should a # 57 (.047) not .470 Thats nearly a 1/2 inch!! Please be carful

Nogyro

My Feedback: (10)

Glad you caught that one 85 bipe. I didn't notice his decimal point being off by one.

Scoubidou

My Feedback: (17)

Nogyro
Did you use the drill bits included in the Hobbico pin vise to do the carb mod? I bought the 1/16 pin vise but all drill bit are too small?
Drill bit included:
One #52 pin vise drill bit.(nearly 1/16")
One #56 pin vise drill bit.
One #60 pin vise drill bit.
One #64 pin vise drill bit.
One #70 pin vise drill bit.
One #80 pin vise drill bit.

you recommended following bits 0.035=#65, 0.040=#60, 0.043=#57, 0.046=#56
http://bobmay.astronomy.net/misc/drillchart.htm

If i take the bigger drill bit that comes with the pin (bit#52), the high needle valve hole is still bigger?

The high needle diameter hole is near 1/16'' and the low needle hole diameter is smaller.

Did you order separate drill bit to do the job? How much did you pay for a WT76?
Daniel

Antique

My Feedback: (4)

The final size of the hole determines how many turns the needle will have to be opened...If the hole is way too big you might end up with the high needle open only 1/4 turn...Not a really big problem except the needle might get touchy....If the end of the needle had a nice straight taper like a glow carb it would be easier, but most don't...I sometimes re grind the carb needle taper when converting to glow, makes it easier to adjust....
After modifying the carb you will NOT be using the "factory" settings..Bad news for those who are afraid to touch the "factory" settings...

Scoubidou

My Feedback: (17)

Ralf
I think i am going to try with what i already have instead of waiting and purchasing other drill bits. What do you think about the 1/16'' drill bit? Is there some risks to breake or to crack the carb with the 1/16 bit and dremel tool?

With 1/16 bit, i am going to be near 1/2 turn..[>:]

chichisport

There is a better tool for these , its called tapered reamer , Most racing shops will have in stock . Mines cames from westechnik . Usefull for many things.

Nogyro

My Feedback: (10)

Scoub,

Yes, I used the bits that came with the pin vise. I did not use the largest one though. I test ran the engine after each drilling, and the .046 dia. bit gave me what I wanted, so I stopped there. I gave the diameter of the bits I used, so there wouldn't be any confusion on what size they were...........If in doubt, mic the bits, that's what I did. I've found that after the carb is drilled out with the .046", I'm running my high needle at 1 3/4 turn or so. 2 turns appears to be wide open, so I don't know if you drilled it out with the 1/16" bit(.0625) whether or not the needle would have enough taper to shut the fuel off. Same thing Ralph says...........

mstroh3961

My Feedback: (4)

Nogyro, I'm curious, Have you discussed your results with DA?

Nogyro

My Feedback: (10)

I returned the old carb to them last week and included a detailed account of my results with both the WT76 carb and the drilled out hs fuel passage on the stock WT201. They received it last wed. but they haven't contacted me..................

Scoubidou

My Feedback: (17)

I bought my DA last year and the high speed fuel passage diameter is 3/64'' (measured the best i can with a rule). My carb is WT210B. Maybe the 201T carb has bigger hole than 201??

I am at 200 feet sea level for that reason, i need more fuel than Nogyro at 450 feet. I run Menz 22x8 at 6950 RPM hot with slimline but i can not go on the rich side.

I am going to drill with 1/16 bit. 1/16-3/64''=0.0156'' and only 1/64''. I hope it will work?[]
Daniel

Scoubidou

My Feedback: (17)

Oups mistake. My carb is WT201B with 311 number?

Nogyro

My Feedback: (10)

WT201B.....B stands for primer bulb which we don't need, they remove it. 311 stands for the lot number.......I believe one of mine was 301, and the other was 421 or something like that.

Antique

My Feedback: (4)

The tapered part of the high speed needle on a WT76 is .058 long, then it's almost a right angle to the straight part of the needle, which is .076..If you drill out the hole to 1/16 (.060) you will make the high speed needle ALMOST useless...Even .046 is way larger than the widest part of the taper, about .040 on a WT76...The needle on the stock 201 carb may be a straight taper, so .046 worked...Carbs are not cheap, you could end up buying another...
I don't have a 201 to look at.....[8D]

Nogyro

My Feedback: (10)

The taper on the WT201 hs needle is also .040 at the widest part....Looked like the same needle as the WT76. I measured this also before I did the drilling. jI figured since the original hs fuel passage was .035, and we had the needle backed out all the way, .046 would be about right. You could still shut it down to .006 opening in theory with the needle all the way closed.......

Scoubidou

My Feedback: (17)

I don not know what's wrong with my carb but mine is 3/64''=0.468 and i can not go on the rich side whatever 2 or 5 turns and the TOP RPM stayed the same. I drilled it to 1/16'' this morning and i'll try it tomorrow after work. In the worst case, i am going to order a WT 76.

Keep in touch.
Daniel

Antique

My Feedback: (4)

A big prop on a small engine will have the same effect, no amount of adjusting will make it rich enough to slow down..Just for kicks try a 20-10 prop, the usual size for a 50cc engine..[8D]

Scoubidou

My Feedback: (17)

Here is a pic:
I drilled the bigger hole in the top right of the carb (high needle fuel port). It seems to have an angle of 30 degres with that hole.

Nogyro

My Feedback: (10)

I left that hole alone. I believe it was something like .060 or .070. As long as the hs passage was smaller than that, the inner hole would be the limiting factor on how much fuel would pass through the system.......ASSUMING the main jet is larger than that.....

Josey Wales

My Feedback: (61)

Did you have to change your linkages with the new carb?

Nogyro

My Feedback: (10)

The red anodized arm for the throttle screws right on the WT76 throttle arm. The choke lever has a larger hole in it, 3/16" or so, which is too big for installing a ball link, so I swapped out choke shafts between the WT201 and the WT76. I didn't have to change linkages at all that way.