RunRyder - G-231 RPM Hunting issue resolved, a must read

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Gasser Model RC Helicopters > G-231 RPM Hunting issue resolved, a must read

ccm15
Senior Heliman
Location: Lake Ariel, PA

Ok, I know I have had a two page post earlier with my problem of my 231-PUH getting hot after a few minutes of hovering and having the RPM hunting all over while idling. After replacing the carb, installing a Z-RC insulator and multiple other changes including installing a brand new engine, I have found the culprit.

This pertains to most of us with the Spectra G. I found that the supplied in tank filter part # 125-22 has been my problem the whole time. This may not effect all operators of this part. I am still breaking in my engine and running rich so there is some vibration and fuel foaming. With the fuel foaming and at about half tank or less of fuel the in tank filter is sucking air due to the fuel foaming. This is causing tiny air bubbles in the line making the engine run very lean and hot. I removed the stock filter/pickup and replaced it with a standard Dubro clunk and same id fuel line as I use on the rest of the fuel system. I flew the machine four times each time 10 minutes today with no problems. Before the fix my engine was running real hot at about 350 degrees. Now it is down to around 200 and running beautifully. After all I had changed this was the ONLY thing I overlooked. You don't even want to know how many times I removed the engine from the airframe lol. Thank god for the wonderful engineering of the Spectra I can remove and engine in about 10 minutes.

I have herd a few people lately with there engines running erratically so I hope this helps.

One mile of road will take you one mile. One mile of runway will take you anywhere in the world.

09-08-2008 02:21 AM

Excalibur
Veteran
Location: Destination: Earth

Interesting. . .

I'm just finishing installing a 16oz Dubro tank under the battery tray, but not using the supplied clunk/filter. On previous posts it has been determined that it is better to use a felt-type clunk. I also used a layer of thick 3M double-sided foam tape between the tank and fuel tray to help mitigate any vibration problems. Guess I'll find out how the whole setup works when I get it in the air. . .

Xcal

Camper Fuel: It's Not Just for Breakfast Anymore

09-08-2008 05:24 AM

shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Ccm15

Glad you have found the problem,strange how these problems usually turn out to be a basic and simple problem in the end.I sometimes wonder whether on some heli,s if the size and bore of the petrol pipes are big enough to flow enough fuel at high demand.I have had similar problems and i noticed that if i had a poor idle if i pumped the fuel primer slowly the engine would run perfectly.I changed the clunk for a larger bore(without a filter)replaced the pipe with largest bore i could find for this application.I fitted an inline filter(High Quality)i bought from a garden machinery store.IHMO i think that the universal fuel filters are sometimes too fine a mesh for petrol and need a proper high flow filter designed for the job.If you have brass fittings that go into your tank pay attention to the bore as this can act as a bottle neck on supply and return.I have modded both my gassers and they no longer suffer with surging and overheating due to a leaning mixture.I also fitted a heat shield between the inlet tract and the cylinder head to help isolate the carb from excessive cyl head temps.

09-08-2008 10:00 AM

ccm15
Senior Heliman
Location: Lake Ariel, PA

[B]Excalibur

I am also using the Dubro 16 oz tank and soft mounted it to minimize vibration. I will probably go get the Walbro felt clunk as soon as I can find one. Your set up should work fine. Oh also get rid of the small id fuel line supplied with the kit for the inside of the tank. it looks like fuel line for a Cox .049 engine.

One mile of road will take you one mile. One mile of runway will take you anywhere in the world.

09-08-2008 12:11 PM

Excalibur
Veteran
Location: Destination: Earth

Quote
Oh also get rid of the small id fuel line supplied with the kit for the inside of the tank. it looks like fuel line for a Cox .049 engine.

Ya know, I can't imagine that the smaller diameter fuel tubing inside the tank could cause flow problems. If a gasser can run 15 to 20 minutes on a 16oz tank, the flow through that tube is incredibly slow, regardless of size.

Now, I DO believe that the clunk can have a lot to do with flow problems, as has been detailed here by Raja and others, and indeed by yourself. The whole reason to use the smaller, more flexible tubing inside the tank is to allow the clunk to easily follow the fuel around as it shifts do to gravity, centrifugal force, etc. I used it in my Predator Gasser with great success. A larger (stiffer) fuel line inside the tank could potentially cause a dead-stick when there is still plenty of fuel remaining, due to sloshing or maneuvering.

I definitely think you're on the right track with the clunk though. Keep us posted on the results.

Xcal

Camper Fuel: It's Not Just for Breakfast Anymore

09-09-2008 05:52 AM

rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

Personally I don't use that tiny diameter fuel line in the tank

In fact, while debudding Paul's crappy running Spectra-g this past weekend at The gathering in Atlantic city I made him take out the thin line and replace it with the next size up tygon tubing.

I like to get fuel flow to my engine and I've found that its not necessary for the clunk to flop in all directions as the felt clunks pickup fuel even from fuel splash.

Granted after a 15 minute flight when you're at a 1/4 tank or less its going to get harder and harder to get a consistent flow with the clunk stuck on the back side of the tank, but I 3D for 15 minutes and land not running the tank down to the end and it works for me.

-=>Raja.

1005 Xcell Gas, BHH G26 3D Plus, Jewel Generator
Spectra-g, BHH G26 3D Plus, Jewel Generator

09-09-2008 03:46 PM

shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Walbro felt clunk

Can anyone tell me where to obtain a couple of these.

09-09-2008 04:06 PM

ccm15
Senior Heliman
Location: Lake Ariel, PA

Most small engine and lawn mower repair stores carry the filters. you can also do a Google seach for Walbro 615-92. I was able to order them online from a choice of placed. Good luck.

One mile of road will take you one mile. One mile of runway will take you anywhere in the world.

09-09-2008 11:35 PM

shawmcky
Senior Heliman
Location: Isle of Wight,United Kingdom

Walbro felt clunk

Thankyou for that,i never thought of trying the mower stores for the clunk,i will try them first.

09-10-2008 08:58 AM

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Gasser Model RC Helicopters > G-231 RPM Hunting issue resolved, a must read

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