carby problem

[mickmurphy]

Gday i have a spectra with a 231 motor with a 643 carby i was flying on sunday and noticed that the motor started to lean out i landed and checked the fuel pump on the carby it was empty i pumped it and a few mins later it was empty again i have ran about 8 galons throw the motor the carby is clean. has this happend to others and how did you fix the problem

thanks mick :cool:

[DebianDog]

Check the tank and lines for an air leak. :wink:

[mickmurphy]

thanks i will have a look at the lines :cool:

[ClayK]

Also check filter.

[CustomPC]

Mick,

How long had you been running the motor when the primer bulb drained?

Carey Shurley has written 2 articles about the Spectra-G in Rotary magazine.

In the 2nd of those articles (Jul-Aug issue) he says that you can have this exact problem if you don't use the carbon deflector plate (that MA supply in the kit) between the insulator block and carb.

He says that hot air coming from around the cylinder will heat the carb to the point where the bulb will drain and the carb will lean.

I have asked him via PM if you should still use the carbon plate when using the Z-RC insulator and said he's still testing the Z-RC so hasn't formed an opinion about that yet, but suggest to use the plate.

[Rodney]

I dont fly M/A but I know we have the same motor, that carbon plate is not used by me and i have no problems with the 231 and 643 carb. I was using a Carbon Airfilter assy. tho.

[mickmurphy]

Gday guys thanks for your input i have gone all out and replaced all the fuel line i have taken out the T pices that you get inthe kit i all so changed both diaphragms + gaskets cleaned the filter i have not tryed it yet but i will let you know what happens i don't run the carbon plate with my Z-RC insulator i know a few people how has spectra-g's and thay don't run it neather now i have the old 230 motor in my ergo i have put the 677 carby on and "MAN" it go's hard my air filters on both are the ones from MA

Thanks mick :cool:

[bigrcr]

A 677 that actually works! WoW! :WOW

I would bet your problem was in the clunk line or the fuel bulb itself. If the fuel bulb has some age on it or is not seated well, it will empty. The 643, 644 and 645 carbs are choice. The 677 is very problematic (it has virtually no transition) and really should not be used on the motor for our use (it is a purpose built lean running carb).

Later,

[mickmurphy]

still have not tryed it yet it is rainning here in sydney austraila. the 677 is working fine it did not work to well on the 231 but on the 230 it is working it is giving a bit more power with it :cool:

mick :cool:

[CustomPC]

Mick,

I had exactly the same problem with my spectra today immediately after installing the Z-RC insulator.

I had a great morning flying with the stock insulator and installed the Z-RC to see what effect it would have. First flight out i noticed the bulb was dry. Second flight, same problem.

I removed and checked the seals on the Z-RC and everything looked fine so re-installed it againg. Another flight and this time the bulb drained again and i couldn't kill the motor. I had to pull the fuel line.

I put the stock insulator back on and flew the rest of the afternoon with no problems.

[mickmurphy]

Gday guys i am still the problem have changed all the fuel lines if i went into a hover no problem as soon as i started working the throttle it started to empty out and rpm started to rise i have now rebuilt the carby i have not tryed it yet if it dose not work i will change the carby to a 644 and see what happens.

mich :arggg:

[bigrcr]

What are the air temperatures that you are flying in? It seems to me the problems are happening in Australia. :?
I would think that you are all having problems from "vapor lock" where the temperatures are high enough to basically vaporise the fuel before it can be properly distributed in the carb. A symptom of this would be the fuel bulb emptying as you describe and of course, leaning problems following this. Try using the carbon isolator plate to keep some of the radiant heat off of the fuel bulb (the plate that came with the kit) if you are not using it.

Is the carb itself hot to the touch when/as/after this happens??

Later,

[CustomPC]

Hi John,

Temps were forcast for 17 Celcius yesterday i think.

Carey Shurley tells me the same thing about using the carbon plate. I forgot to mention that i am using it with the stock insulator. I tried the Z-RC without it at first and then with it. Without the plate i got the bulb draining problem. With the plate the bulb was full but got what i presume is an air leak because the idle was surging and i couldn't kill the engine.

The Z-RC was very warm-hot to touch and the carb was warm but not hot. (this was about 1 minute after shutting the engine down.) I'm using stainless bolts to mount the carb. I doubt they cause a problem but there's a slim chance the bolts might be transferring some heat.

[bigrcr]

Good. You are thinking along the right lines. At that temperature, you should not be having problems. :?

I found the same thing using the plate; it does keep the bulb from seeing the heat, but it can cause a leak. Try using new gaskets on each side of the plate if you use it and possibly seal it with something (gasket sealer?) so that air does not leak past the plate.

Try richening up the high needle until there is a drop in power; then go back to the last good setting. In other words richen up all you can to reduce the heat.

Hope this helps!

[CustomPC]

I'm back with the stock insulator and the carbon plate with new paper gaskets and the engine is performing well. In fact, now tweaking the needles yeilds the expected results and the engine is now very predictable.


I think i'm still slightly rich. I have the tiniest of tail wag at hover. No bogging at the start of a climbout and no spluttering at the top. No overspeeding on decent either so i must be close.

The plug is a dark chocolate to almost black colour but that might be due to too much oil (Redline Two-Stroke Racing Oil at 32:1).
The ceramic on the plug is smooth and dry, not wet or powdery/matt.

[bigrcr]

:wink: :D :glasses2:

[mickmurphy]

Gday guys i have only had this problem happen. I am running the z-rc insulator.I don't run the carbon plate and i know overs ho run there's the same way with no problem :arggg: but my ergo with the a Z230/677 carby no problem. I am going to check the over filter and see what happen's

mick :arggg:

[CustomPC]

Hi Mick,

What oil ratio are you running?

I put the Z-RC insulator back on my heli and over the course of 2 weekends i have determined that the bulb drains in flight when i'm running a 50:1 mix.

If i increase the oil content to 40:1 it eliminates the problem.

This happened for me with 2 different oils. Red Line 2-Stroke racing oil and Motorex Cross Power 2T.

I'm back onto the Motorex oil now as it seems to burn much cleaner than the Red Line.

[mickmurphy]

guys the problem is fixed is was the oil ratio i have gone back to 25/1

thank for the help :cool:

mick