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JR-Spektrum . E-flite . Fast Lad Performance

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Gasser Model RC Helicopters > 231PUH RPM ?
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

My Posts This: Topic  Forum

Quote 
what else in the carb could stop working when it gets warm and work again when cool?

Rich setting or a needle seat that doesn't close completely. When the engine is cold it needs more fuel so if you have the needle set rich or the needle seat is leaking a little it helps starting. Once the engine is warm you can't get it started because the mixture is too rich. If you did get it to start it might appear to run fine.

This is where people start opening up the throttle to find it will start (essentially leaning the mixture) but it is not a good idea as you should expect a hot start.

Ace
What could be more fun?
11-01-2009 11:38 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Nice theory Ace but these carbs have never seen any work or mistreatment with the needles; I can put three different carbs on this Heli ( two of them new) and have the same thing happen.

I only like to fly gassed up
11-02-2009 12:16 AM
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AceBird
Elite Veteran
Location: Utica, NY USA

My Posts This: Topic  Forum		I am only trying to spit out the possibilities.

So if you set up all three carbs to be very rich on the low needle then you would be expecting the same problem. Again this is just a possibility.

What happens if you pull the plug and squirt some fuel into the cylinder? Will it start in four or five pulls? That tells you if you have too much fuel or not enough. Then you know what to look for.

Ace
What could be more fun?
11-02-2009 01:37 PM
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j.8
Veteran
Location: Denmark

My Posts This: Topic  Forum		Hi Fixit

When you idle your engien, and tilt the heli,
on the ground, up on one skid, is there any
change in engien rpm.


Regards Bo
11-02-2009 01:51 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
What happens if you pull the plug and squirt some fuel into the cylinder? Will it start in four or five pulls? That tells you if you have too much fuel or not enough. Then you know what to look for.

I haven’t tried that and don’t really see a need to,Why? because the motor starts after two pulls every time, one with the choke on then it starts with the next pull, the needles aren’t set rich and the heli fly’s pretty much perfect for one or two flights then it starts to lean out and on landing the bulb is empty and wont prime again until I cools down.

I only like to fly gassed up
11-02-2009 03:55 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
When you idle your engien, and tilt the heli,
on the ground, up on one skid, is there any
change in engien rpm.
I would have to try that first j.8 before I could give you the answer, what would that prove?

I only like to fly gassed up
11-02-2009 03:59 PM
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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

My Posts This: Topic  Forum		I got an answer for 1/2 your symptoms

A heli motor that runs well for the first two minutes and then leans out is a motor with a bad seal at the bearings - usually the front bearing seal is not holding.

I say half because I don't know for sure about the not priming any more part, but I would say as I always do if you fix the obvious first, then the non-obvious may go away with it as well. In your case fixing a bearing leak is not exactly an easy task, but what you could try is to pull the motor out, replace it with another, and see if the rest of the parts are OK - like use your carb that isn't priming on the new motor along with your insulator and gaskets.

If the new motor works, then I'm right the old motor needs the bearing seals fixed.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights
11-02-2009 04:04 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Hi Raja

I have two motors both have only just been run in and the carbs act the same on both, I need to try the mod to the cooling shroud before I do anything else and see if that helps, the bulb will prime on or off the engine when it's cold so a bearing seal on the motor would have no effect on the carb problem, I'm sure its either hot air blowing over the carb or a diaphragm fault but don’t forget these were both bought new and have only run 5 gall at most.

PS, I have a third carb I also bought new and that acts the same when on this Heli, the engine rpm is a little low at 11,000 but the engine isn’t running hot and the piston is still like new

I only like to fly gassed up
11-02-2009 04:28 PM
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j.8
Veteran
Location: Denmark

My Posts This: Topic  Forum		Hi Fixit

Quote 
Quote 
When you idle your engien, and tilt the heli,
on the ground, up on one skid, is there any
change in engien rpm.
I would have to try that first j.8 before I could give you the answer, what would that prove?

Raja allready answered that, leaking bearing.

Another thing is, that when tightning the 4 small
bolts/screws that holds the metal plate, wich keeps
the primer bulb inplace, be careful not to over tight,
because that will make the metal plate curve, and that
can cause an air leak aswell.


Regards Bo
11-02-2009 04:48 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum		OK, but I’ve already pinpointed the problem to the carb not priming when it gets warm and just need to find out why
If I fit a cold carb after landing the motor fly’s perfect until the carb warms up again

I only like to fly gassed up
11-02-2009 04:57 PM
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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

My Posts This: Topic  Forum		What is this that you're flying?

Is it a trex gas conversion of your own? The carb hot issue doesn't happen on all the "production" designs, so if indeed that is your case well its a localized issue to your design.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights
11-02-2009 07:29 PM
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j.8
Veteran
Location: Denmark

My Posts This: Topic  Forum		Hi

Yes, like Rajs says.

When I look at the picture on page 2, I can some holes
in the base plate, under the fins, you might try and
drill some more, because when the air has pased the topend
it needs to go somewhere, and if the air can`t pass through
the base plate, it will be blowen out on each side instead,
and that can cause the fuel to evaporate in the carburator.

When you say "carburator warms up" how warm a carburator
are we talking about

Regards Bo
11-02-2009 07:40 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
Is it a trex gas conversion of your own? The carb hot issue doesn't happen on all the "production" designs, so if indeed that is your case well its a localized issue to your design.
Yes I have been thinking it is a design problem of mine and like you say It doesn’t happen on most has I've owned most of them in the past without having this problem

I only like to fly gassed up
11-02-2009 08:13 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
When I look at the picture on page 2, I can some holes
in the base plate, under the fins, you might try and
drill some more, because when the air has pased the topend
it needs to go somewhere, and if the air can`t pass through
the base plate, it will be blowen out on each side instead,
and that can cause the fuel to evaporate in the carburator.

Your right about the holes in the base and when I fit the shroud extension yesterday I also joined all the holes and cut it out so now it's a large hole and I'm hoping this might help solve the problem.
The hole needs tidying when I take the base off next time.



Quote 
When you say "carburator warms up" how warm a carburator
are we talking about
I haven’t had a temp reading but it’s not hot so you can’t handle it, I had thought about using a hot air gun on the carb to see if I can imitate the problem on the bench

I only like to fly gassed up
11-02-2009 08:20 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Looking a little better now


I only like to fly gassed up
11-02-2009 10:25 PM
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AceBird
Elite Veteran
Location: Utica, NY USA

My Posts This: Topic  Forum		Wow that's bad news. You shouldn't be restricting that air at all. Anything in the way is asking for trouble. You may not think it is not overheating but I would bet it is if not just locally.

Ace
What could be more fun?
11-02-2009 10:29 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
Wow that's bad news. You shouldn't be restricting that air at all. Anything in the way is asking for trouble. You may not think it is not overheating but I would bet it is if not just locally.
Have you seen the Spectra G base



I only like to fly gassed up
11-02-2009 10:50 PM
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AceBird
Elite Veteran
Location: Utica, NY USA

My Posts This: Topic  Forum		Did I tell you there is a lot of things about the Spectra G I don't like?

In the picture of your plate the fins look much closer to the plate. That may be an illusion. However anything in the way of the exiting air will deflect the stream and reduce the flow of air. Neither one is good.

Ace
What could be more fun?
11-03-2009 01:15 PM
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j.8
Veteran
Location: Denmark

My Posts This: Topic  Forum		Hi Fixit

Quote 
Looking a little better now

Yes absolutely, looking forward to hear if
that helps sorting out the problem.

It`s allways interresting when people make
there own conversions, and we can all learn
alot from that.

Regards Bo
11-03-2009 01:27 PM
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Fixit
Elite Veteran
Location: UK

My Posts This: Topic  Forum
Quote 
In the picture of your plate the fins look much closer to the plate. That may be an illusion. However anything in the way of the exiting air will deflect the stream and reduce the flow of air. Neither one is good.

It’s a bit off an illusion Ace, the spectra engine stands on its own mounting plate on top of the base so its 3 or 4mm Higher than mine, not a vast difference but Higher is better than lower.

I only like to fly gassed up
11-03-2009 02:22 PM
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5 pages [ <<    <     1      2     ( 3 )     4      5     NEXT    >> ]1546 viewsPOST REPLY
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Gasser Model RC Helicopters > 231PUH RPM ?
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