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carb rebuilding

Old 06-21-2009, 11:07 AM
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kahn41
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Default carb rebuilding

I am in the process of rebuilding a walbro carb, and my question is. the second you start to push down on the float needle lever arm should the float needle immediately begin to come up? I have some slop in this one. I can push on the metering arm and there is a little less than a 1/16 of an inch slop before the float needle begins to rise!!! I have seen this many times on walbro's I thought there should be next to zero tolerance on the metering arm and the float needle!
Old 06-21-2009, 12:28 PM
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Nosedragger
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Default RE: carb rebuilding

there should be some slop
Old 06-21-2009, 12:45 PM
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kahn41
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Default RE: carb rebuilding

I thought there might be. Now I have fuel leaking out the muffler, the new float needle does not want to seat properly.. Another question! 3rd time I hade the carb tore down to get the float needle to seat anyone know the correct procedure to do this???
Old 06-21-2009, 01:23 PM
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skip1320
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Default RE: carb rebuilding

Sound like its not the needle and seat,probably an internal leak not worth fixing,welch plug,high speed jet,what size engine is it?,good luck
Old 06-21-2009, 01:30 PM
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Nosedragger
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Default RE: carb rebuilding

Pop off test will confirm  if the needle is closing correctly.
The needle just drops in the hole, if not there may be varnish build up from old oil /gas.The metering lever with its  spring pressure holds it shut. It does not have to open it as the fuel pressure will push it open as soon as the metering lever releases pressure holding it closed.
Old 06-21-2009, 02:13 PM
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kahn41
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Default RE: carb rebuilding

its a 36cc brillelli, I dissassembled it, took the needle out again reinstalled and now it didnt leak in an hour and a half... I'm guessing all is fine
What is a pop off test?
Old 06-21-2009, 03:11 PM
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Default RE: carb rebuilding

pressure test to check the psi needed to force the needle off its seat against the spring pressure, uses pump and a hose availible from walbro.
walbro service manual C-1022 shows how this is done. The manual is availible for free .pdf download from the walbro web site.
Old 06-22-2009, 12:10 AM
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freeair
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Default RE: carb rebuilding

what you must be very cautious of with this type of pump carby is premature wear of the needle in seat due to vibrations from the engine. there are 2 types of needles available , one is the full metal type and the other is a rubber tip type. lets say your carby is mounted so the needle tip is facing down, this position will cause premature wear of the needle compared to if the carby was mounted with needle tip facing up. so needle down go for the rubber tip needle . also be carefull of the chrome plating that comes off this needle after some time as the small fragments will block the seat. i have a couple of non genuine Walbro carbs that i have replaced with genuine walbro parts such as the complete diaphram kit and needle, they work fine.
Old 06-22-2009, 04:35 PM
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kahn41
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Default RE: carb rebuilding

nosedragger
For the life of me I cant seem to locate the pdf file you are refering  too! Everthing I have found is a manual that you have to purchase. Would you by chance have the link that you could post?
Old 06-23-2009, 10:44 AM
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Default RE: carb rebuilding

Here is the link for the Walbro site.  Pick out your carb, you can also click on the diaphram crab to see the pop off procedure that was mentioned.
http://wem.walbro.com/distributors/servicemanuals/
Old 06-23-2009, 11:09 AM
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Nosedragger
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Default RE: carb rebuilding

http://wem.walbro.com/distributors/s...viceManual.pdf

takes a while for it to load
Old 06-23-2009, 03:21 PM
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kahn41
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Default RE: carb rebuilding

thank you nosedragger............. You are the man!
Old 06-23-2009, 03:49 PM
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Default RE: carb rebuilding

You're welcome.
Old 06-24-2009, 09:39 AM
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Default RE: carb rebuilding

If you hold down on the needle, the arm should be about level with the machined surface of the carb body. I did the same thing you did. I thought the less slop there was the better(in some things that is true! ;-) ). I had the carb flooding until a local small motor man told me how to set it.
Old 07-02-2009, 07:52 AM
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GeraldRosebery
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Default RE: carb rebuilding

If you have a lot of problems with fuel leaks even after rebuilding, just replace the carb. Cost is only about $45 and is the airplane not worth having a reliable engine? Try the Walbro WT201-1 carb used on some 40-50 cc engines. It works very well. Check out:

http://www.m-and-d.com/WL-WT-201-1.html

Gerry Rosebery
Old 07-02-2009, 02:18 PM
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kahn41
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Default RE: carb rebuilding

thanks Gerald, i'll bookmark the site when the time comes to buy!!! Everything is fine now, no leaks runs great

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