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HelicopterGasser Model RC HelicoptersOther › Walbro WT-643 Problem - Now Something Else
09-04-2009 05:03 PM  8 years agoPost 1
carpman

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Spain

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Well I am back in the air but now having carb problems that I have never had before...

Could someone maybe give me a check list of things to look over for the following problem. Only thing I am pretty sure of is that there are no air leaks...

Basically from cold the primer bulb will fill, minutes into a flight it is empty and when warm will not fill. Small pin head bubbles can be seen, which I thought must be an air leak. Dirty filters maybe I don't know as I am delving where I have never been before but am keen to understand what's going on...

I have the carb in bits and see 2 large screens each side of the WT-643 and another seems to be held in the carb...

Please if anyone can walk me through what this might be?

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-04-2009 05:32 PM  8 years agoPost 2
Chris Bergen

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cassopolis, MI USA

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How's the engine running?

Chris D. Bergen

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09-04-2009 06:52 PM  8 years agoPost 3
carpman

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Spain

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It was running fine but since this it starts to lean out and speed up...

When removing the 4 screws from the bulb side, they weren't loose, but they were not tight either, maybe enough to cause the pin head bubbles?

While it's apart I may as well try and clean whatever I am supposed to clean before reassembly and running her up again.

Failing that I have another carb I can try, this will tell me if it is the carb or something else I guess?

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-04-2009 07:11 PM  8 years agoPost 4
Chris Bergen

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cassopolis, MI USA

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It was running fine but since this it starts to lean out and speed up...
Is the leaning out a RESULT of the carb emptying, or vice versa?

Possibly the leaning of the engine and subsequent rise in temp CAUSES the bulb to go empty...

???

Chris D. Bergen

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09-04-2009 07:33 PM  8 years agoPost 5
carpman

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Spain

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Hi Chris

I would say that the temperature is not the cause of the bulb emptying, as the first post I cannot even prime it on the ground after a few minutes flying, only when cold.

Definitely the bulb emptying through some other reason (blockage, air leak) causing the motor to run lean and speed up...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-04-2009 07:57 PM  8 years agoPost 6
shawmcky

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Isle of Wight,United Kingdom

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Is your vent line clear?

Is your in tank pipe good?Return line clear?

Team- unbiased opinion.K.I.S.S principle upheld here

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09-04-2009 08:44 PM  8 years agoPost 7
carpman

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Spain

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Yes shawmcky all lines are good, I actually had a tank leak yesterday and thought that may have been it. However I fixed that today but still have the carb problem...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-04-2009 08:51 PM  8 years agoPost 8
shawmcky

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Isle of Wight,United Kingdom

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carpman

Do a search for Walbro tune up or Walbro carb repair on-line,lots of helpfull walkthru,s for our carbs.

Team- unbiased opinion.K.I.S.S principle upheld here

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09-05-2009 07:26 AM  8 years agoPost 9
SeismicCWave

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Hilo, Hawaii

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Carpman,

Before you put it back together go to your local lawn mower shop and get yourself a rebuilt kit for the carburetor. You need to replace some of those gaskets once you take it apart. I also found that there is a piece of thin gasket/valve material on the pump side that needs to be changed. It has two little flaps that act as one way valves. If those valves are not sealing the pump will push some air through the circuit.

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09-05-2009 08:09 AM  8 years agoPost 10
carpman

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Spain

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SeismicCWave that certainly sounds like it could be an issue and why I see the little pin prick bubbles in the bulb.

However as we are not as lucky as you guys I will have to order and wait 2 weeks for a repair kit, so in the meantime I will clean it and put it back together and see what happens. If still no joy I have a carb on a spare motor that I can try, that will at least tell me if it is the carb or something else...

What else if anything can cause those bubbles...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 08:38 AM  8 years agoPost 11
SeismicCWave

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Hilo, Hawaii

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>>What else if anything can cause those bubbles...<<

Really can't tell you. I just buy a new carburetor.;-)

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09-05-2009 08:56 AM  8 years agoPost 12
carpman

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Spain

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What is the reference number for the repair kit for a WT-643?

I can find them but there are loads of different reference numbers that say they are for WT carbs, talk about confusing...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 01:40 PM  8 years agoPost 13
carpman

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Spain

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Seems to be sorted, what did I do?

I cleaned the screens and when I reassembled the bulb I nipped the screws up a bit tighter. As mentioned above I think this may have been the issue.

...real test later today or tomorrow...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 04:42 PM  8 years agoPost 14
carpman

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Spain

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THROTTLE SERVO, WHAT GIVES!

The Spectra is relegated to a back seat for the minute it is driving me nuts at the moment...

Why?

Sorted the carb I hope, so I thought while I was there I would sort out and check the throttle linkage.

Using a S9252 on the throttle and something weird is happening, I noticed that with ATV's at 110% low and 120% high the servo operates fine, however when I cut the motor with the trim it loses control. How can I explain this so you know what I mean.... basically it just spins free and is not locked? If I put the trim up or reduce the ATV to 100% its fine and you can see and hear it lock back in...

Its like the servo is been over driven or something I don't understand this. Has something gone wrong with the servo, is this normal, do I just set the ATV at 100% and not worry about it? Had it all in bits and gears are fine...

Really getting tired of this at the moment, 100 trouble free flights and now one thing after another...

All I want to do is go flying

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 05:04 PM  8 years agoPost 15
rbort

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Franklin, MA - USA

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Throttle servos can fail

My 9252 lasted quite a long time, over 300 flights and I just recently replaced it with another.

If its not holding position in a hover or at idle or somewhere else, replace it with another.

-=>Raja.

MA 1005 Hanson 280, 4129 flts
Spectra 27 3DMax, 3187 flts
Whiplash V1 Hanson 300, 1425 flts
Whiplash V2 Hanson 300, 185 flts

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09-05-2009 05:13 PM  8 years agoPost 16
carpman

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Spain

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Just tried something else with it, from 0-50% throttle it moves about 30 degrees, from 50% to 100% it moves about 5 degrees...

I think its just given up, the only other thing would be a signal problem from the GV1 or TX, but I doubt it...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 05:20 PM  8 years agoPost 17
rbort

rrProfessor

Franklin, MA - USA

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Plug another servo

Into the gv-1 port and see if it works right. If so then unscrew the bad servo out of the heli and replace it.

-=>Raja.

MA 1005 Hanson 280, 4129 flts
Spectra 27 3DMax, 3187 flts
Whiplash V1 Hanson 300, 1425 flts
Whiplash V2 Hanson 300, 185 flts

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09-05-2009 05:54 PM  8 years agoPost 18
carpman

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Spain

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Raja do you reckon as a temporary measure a S9452 servo will be okay, in fact what about long term?

I have one that's all plus I have a S9452 with a broken case, but the S9252 case is the same...

KEVIN
Trex 500ESP | Trex 600NSP | Trex 700 Gasser | MA Spectra G

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09-05-2009 06:04 PM  8 years agoPost 19
rbort

rrProfessor

Franklin, MA - USA

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I never tried that

I know that the 8417 is no good.
The 9252 is excellent.
The cheap futaba servos are better than the 8417 but worse than the 9252.
And the cheaper JR digital servos like the 821 are crap.

-=>Raja.

MA 1005 Hanson 280, 4129 flts
Spectra 27 3DMax, 3187 flts
Whiplash V1 Hanson 300, 1425 flts
Whiplash V2 Hanson 300, 185 flts

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09-05-2009 08:02 PM  8 years agoPost 20
gramey

rrApprentice

United Kingdom

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Kevin, hopefully it's just one of those phases that you go through with this succession of little problems and all will be well in the end.
I had that problem of the bulb emptying on one of my 1/5th cars before and it turned out to be a pin prick hole in the diaphragm. With my throttle I tried to get it as per the linkage described regarding Mal's set up but with a linear throttle curve, 0,25,50,75,100 it was revving too high. I'm obviously doing something wrong, again, but I've ended up with 5,15,29,42.5 & 95 to keep my servo end points at 100 - 100.
I know yours has been flying o.k. as it was but I didn't want to be overdriving the servo at either end. I'm using a JR 8311 on the throttle, sorry Raja, because it came new at the right price, but if it faisl I'll get a better one.

Dumb thumb specialist

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