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WALBRO Carburetors - Info for Dummies

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WALBRO Carburetors - Info for Dummies

Old 08-03-2011, 10:58 PM
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Andika
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Default WALBRO Carburetors - Info for Dummies

1- http://helifreak.com/showthread.php?t=326599
2- http://helifreak.com/showthread.php?t=325891



Old 08-03-2011, 11:17 PM
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a1pcfixer
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Default RE: WALBRO Carburetors - Info for Dummies


First link is great, but second one is a bad idea!

Leave that throttle return spring in place and as is;
1) If your linkage ever falls off, it allows your throttle to return to idle
2) Jody claims that without it the throttle shaft wears much faster
3) It has very very little resistance to a throttle servo movement. If
yours can't do the job, get a better throttle servo!
Old 08-04-2011, 09:12 AM
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Default RE: WALBRO Carburetors - Info for Dummies

Man, what an excellent treatise on Walbro carbs, and someone put a hell of a lot of work and thought into creating it! Best I have ever seen! I have to save this for when others ask me questions about Walbro carbs. A very handy reference.

Thanks!

AV8TOR
Old 08-04-2011, 01:56 PM
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Jezmo
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Default RE: WALBRO Carburetors - Info for Dummies

I agree, excellent. I also agree on the comment from Jody about leaving the throttle spring on.

Thanks for links.
Old 08-04-2011, 06:03 PM
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w8ye
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Default RE: WALBRO Carburetors - Info for Dummies

He's not done with it yet . . . . Check back later . . . .
Old 08-05-2011, 04:13 AM
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Default RE: WALBRO Carburetors - Info for Dummies

I see three mistakes in his first posting.
1) the stamped notch in the throttle butterfly valve must lie against the throttle shaft, so the butterfly chamfer will fit exactly in the bore.
2) The high speed jet screen is not meant as a filter. It is a capillary screen that acts as a high speed jet check valve. Fuel can get through, but air cannot.
3) No mention is made of the combined function of the idle jets. They supply fuel AND air, depending on valve position. At full throttle, they still supply fuel to the mixture, because the pressure downstream of the venturi is still lower than the fuel pressure.
Old 08-05-2011, 05:59 AM
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rangerfredbob
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Default RE: WALBRO Carburetors - Info for Dummies

the other thing is the mention of emptying the carb of fuel for storage which is the opposite of what you want to do...
Old 08-05-2011, 07:12 AM
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Default RE: WALBRO Carburetors - Info for Dummies


ORIGINAL: rangerfredbob

the other thing is the mention of emptying the carb of fuel for storage which is the opposite of what you want to do...
While I agree with you completely and always leave the carb wet and never had any trouble doing so, there are a lot of owner's manuals for two stroke gasoline engines which state that you must empty the carb of all fuel if the engine is to set unused for more than a day or two.

Old 08-05-2011, 07:58 AM
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Carey Shurley
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Default RE: WALBRO Carburetors - Info for Dummies

in regards to the "throttle spring", keep in mind that this advice is focused on the model helicopter community and know that there are those there as well that agree with your position on leaving it in place.
its one of those things that what you want to happen when the throttle servo fails depends alot on what attitude your helicopter is most likely to be in if it fails.
    [*]Sport flyers tend to be higher in the air and moving in straight lines. Having the throttle close suddenly usually means you quickly find a spot to auto-rotate to and then you replace the servo[*]Hard 3D pilots tend to be close to the ground and moving in all directions. Having the throttle close suddenly can mean wadding it up into a ball and then you replace a lot of parts on the helicopter[/list]
    The important thing about the column is that its just advice based on what I have seen work for me over the years. If it helps in some way great! If you don't agree ignore it or express your opinion in the column as well.
    Gas helicopters have tended to be a little mysterious as they are niche within a niche. If the information posted helps a few people successfully fly them, I'm happy.
Old 08-05-2011, 08:32 AM
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Default RE: WALBRO Carburetors - Info for Dummies

Took my old chainsaw and weedeater out today...Not run since last year...Put fuel in and both cranked right up with no probem...The chainsaw and weedeater both had old fuel in the carb...
Run the fuel dry, or not...No problem either way....NO ethanol in Arizona gas....
The return spring is to return the chainsaw to idle when the trigger is released,and to keep the plate centered on the carb bore...Take it off and the plate and carb body will wear...Not right away, but it WILL wear both sides of the plate and the bore...You want to see some see some ??
Old 08-05-2011, 08:37 AM
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Default RE: WALBRO Carburetors - Info for Dummies

I don't know Ralph.... a lot of the pumps here in Tucson say "FUEL MAY CONTAIN UP TO 10% ALCOHOL".

I have had lots of carb problems in the past before I went to using my "Storage Fuel", and I fix hundreds of yard machine carbs and fuel systems that have degraded because of something in the fuel around here...

AV8TOR
Old 08-05-2011, 08:43 AM
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Default RE: WALBRO Carburetors - Info for Dummies

Tucson has always been a strange place anyway
I guess different parts of all states have different fuel mixes...No ethanol here in Williams, not sure about Flagstaff...Phoenix, Yes...Used to have MTBE years ago....@#$%^& politicians..
Old 08-05-2011, 08:49 AM
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Default RE: WALBRO Carburetors - Info for Dummies

You want to see some see some ??


no I'll accept your posting it as fact

think you're missing my point though.

your concern is that the carb body or shaft will eventually wear.

It will take a long time for that to wear enough to matter and when it does I'll just replace the shaft or the whole carb, they cost $35, I don't care

If however the throttle shuts unexpectedly and crashes the helicopter it will cost hundreds of dollars to repair.

keep in mind its possible for a servo to fail on its first flight.
Old 08-05-2011, 11:11 AM
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Default RE: WALBRO Carburetors - Info for Dummies

True statement
Old 08-05-2011, 11:20 AM
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Default RE: WALBRO Carburetors - Info for Dummies


ORIGINAL: Carey Shurley

You want to see some see some ??


no I'll accept your posting it as fact

think you're missing my point though.

your concern is that the carb body or shaft will eventually wear.

It will take a long time for that to wear enough to matter and when it does I'll just replace the shaft or the whole carb, they cost $35, I don't care

If however the throttle shuts unexpectedly and crashes the helicopter it will cost hundreds of dollars to repair.

keep in mind its possible for a servo to fail on its first flight.
Antique does not miss much....its best to leave the spring on carb shaft. If you servo fails, the heli may be running enough tp put it down safe. You should pratice auto-rotation to land if engine does stop. My friends can do it easy with the Helies they have.
Old 08-05-2011, 01:43 PM
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Default RE: WALBRO Carburetors - Info for Dummies


ORIGINAL: Carey Shurley

You want to see some see some ??


no I'll accept your posting it as fact

think you're missing my point though.

your concern is that the carb body or shaft will eventually wear.

It will take a long time for that to wear enough to matter and when it does I'll just replace the shaft or the whole carb, they cost $35, I don't care

If however the throttle shuts unexpectedly and crashes the helicopter it will cost hundreds of dollars to repair.

keep in mind its possible for a servo to fail on its first flight.
It is not the wear you should be concerned about, but the constant hammering of the throttle valve against the sides of the carb bore does two things:
1) it hammers small flats at the valve sides, so the valve leaks air where it should not.
2) The hammering of the plate against the valve shaft bore will cause deformation of the bore, and binding of the shaft, which is not what you want.

If the spring has to go for one reason or another, the valve shaft should have some form positive stop on both sides of the carb body, without any slop. That way the carb will be in good shape for many flights to come.


Old 08-05-2011, 01:55 PM
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Default RE: WALBRO Carburetors - Info for Dummies

I'm wondering if this has been mis-interpreted

I am NOT recommending that the spring be entirely removed, just the opposite

I am only recommending that the spring tension be relieved

I fully understand the need to keep lateral tension on the shaft which the spring also accomplishes.
Old 08-06-2011, 01:40 AM
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Default RE: WALBRO Carburetors - Info for Dummies

You indeed did not.  I mainly commented  this item in answer to other posters, just to stress the importance and the resulting failure modes.
Old 08-06-2011, 03:26 AM
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Default RE: WALBRO Carburetors - Info for Dummies

thanks for the great discussion guys!

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