30.5cc engine. Maxing out fuel flow on a 1107 carb on my heli. Need more fuel and suggestions

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sm1nts2escape

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Hello everyone. I am running a 1107 carb with the choke removed on a modified 30.5cc TRM engine in my heli. My low speed is perfect at 1 7/8 out but I need a little more fuel on the high needle. As soon as I got past 3 1/2 turns on the high I couldn't get any more fuel out of it and looking for suggestions. If I had to guess I need about 15% more fuel on the high for when I turn the rpm up more. I was just looking into clipping the metering spring but not sure if that will give me the outcome I need. I am new to gassers so all help is appreciated. Looking for more power and more fuel lol. Here is a easy flight on her before she is completely broke in. I am making about 15% more power now than in this video.
 

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Welcome to the forum and I believe your the first here with a chopper like that... just out of curiosity why do you say you require more fuel? Is it bogging or showing signs of fuel starvation up high? Possible elevation issues? And I'd suggest talking with @Seandonato73 he's always spot on with carb issues
 
Thank you! I am running my high needle maxed out at 3 1/2 turns already and I am not completely broken in yet. I could have used an 1/8 turn more on the high today but I simply can't get more fuel out of it and soon the engine will be completely broken in and I want to up the rpm of the engine some more and will definitely need more fuel to do that. As I said I am guessing I need about 15% more fuel to get where I want. I am at sea level.
 
Break in has been a lengthy debate here and isn't really required and as long as ypu have the right oil ratio and letting the engine idle for a few minutes to allow the piston and cylinder to warm up your good... I think what your looking for is not going to come with adding more fuel and.the engine is going to run at its max rpm regardless of how much fuel you throw at it and honestly if you push beyond what the engine manufacture says is max your going to blow your engine
 
RcJunkie13 said:
Go over your fuel system, make sure the tank is vented properly and that there are no pinches in the lines
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I checked over everything three times yesterday and even went as far as trying a brand new carb. My buddies are also maxing out their needles on the same engine and carb as me. We simply need more fuel
I am not trying to limit my rpm. I need more fuel. I need more fuel especially when I raise the rpm of the engine. We use what is called a governor to hold the rpm steady. The rpm is kept constant by an onboard electronic device which controls the throttle directly. I just need more fuel because it is going to be lean when I start raising the rpm beyond what is shown in that flight video.
 
Im still thinking it is not vented properly some how or a line is collapsing under vacuum. I know it is not "needed" but I tell you when I added a header tank to my Trex 600N with on OS55 i could see a noticeable difference for sure...especially when transitioning from inverted flight and in the vertical position. Of course that was on a nitro engine and I think my issue was more around my clunk sucking air...ok I went on a rant here...lol. Curious to see what the final verdict is here.

P.s. what head speed are you trying to govern at? Just a question for my own brain.
 
I would suggest checking your pop off and reset pressures, should be shooting for around 20psi pop off. Walbro makes a spring kit to swap in to get desired pop pressures. I don't reccomend clipping springs, as it increases the spring rate of the spring, and will give lower pop pressure but can increase the reset pressure, which is antagonistic to what your trying to do. Just watch you don't go too far as you'll make needle adjustments very picky.
Edit.
Have a few questions for you.
Unless your running lean (which you are not in the video) more fuel will limit rpm. Are you currently governed at the max rpm you can fuel, and have you tried the max rpm and it ran lean? I fully understand how a governor works and am quite familiar with them, typically you would bypass them to get the carb set up right for max rpm on a 2 stroke. Tune shouldn't change because if a set rpm when the carb is set up properly. So I'm curious as to how you determined you need more fuel to get more rpm?
TODD said:
Sherman
Will send you some info that may help.
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I'd be curious to know what tips you have as well. Always room to learn something new about carbs.
 
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I am currently tuned in perfectly for the governed rpm in that video. I did adjust the tune with the governor disabled to that headpseed. My highspeed is currently wide open now for that same governed headspeed. As the engine is breaking in it is requiring more fuel and at this point I am on the verge of running out of fuel if it seats in even more which I am told the engine still has a few more gallons to go before it is (3gallons more). So with that I know that this carb will eventually not supply enough fuel at the rpm it is currently running at and definitely not enough when I increase the headspeed another 200rpm. Not to mention my post didn't even mention ambient air temp changes.
dougstar said:
Right so please voice your opinion 👍🏻 everyone's entitled to that .....but bs remarks will not fly😤 got nothing nice to say keep your trap shut👍🏻
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Thank you for cleaning things up
Seandonato73 said:
I would suggest checking your pop off and reset pressures, should be shooting for around 20psi pop off. Walbro makes a spring kit to swap in to get desired pop pressures. I don't reccomend clipping springs, as it increases the spring rate of the spring, and will give lower pop pressure but can increase the reset pressure, which is antagonistic to what your trying to do. Just watch you don't go too far as you'll make needle adjustments very picky.
Edit.
Have a few questions for you.
Unless your running lean (which you are not in the video) more fuel will limit rpm. Are you currently governed at the max rpm you can fuel, and have you tried the max rpm and it ran lean? I fully understand how a governor works and am quite familiar with them, typically you would bypass them to get the carb set up right for max rpm on a 2 stroke. Tune shouldn't change because if a set rpm when the carb is set up properly. So I'm curious as to how you determined you need more fuel to get more rpm?

I'd be curious to know what tips you have as well. Always room to learn something new about carbs.
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I am currently looking into this. I called Walbro and left them a voicemail as well as and email.
 
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Seandonato73 said:
I'll add we've also seen a few carbs coming through from the factory with the metering lever height set wrong. Most of them seem to have a lack of fuel issue. Something else to check, and you need the metering lever Guage to set it correctly.
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I ordered the guage and some other stuff today. Will hopefully solve this issue soon. Thank you,
 
Few more questions.
How are you tuning this engine? By ear or tach?

How are you verifying the engine is broke in? Typically this is done via dyno, or even compression readings. 3 + gallons is a lot of fuel for this size of engine for break in, in my experience.

You said you removed the governor and set max engine rpm, therefore your tune should be fine if you raise the set governed speed 200 rpm. This is a negligible amount of rpm, as the governor has full control of throttle plate movement, and just adjusts to maintain set rpm under varying load conditions. (You know this already) so by raising your set governed rpm, your top tune shouldnt effect anything. (This should be set with the throttle plate wide open, under load ideally)
I'm truthfully struggling to see where your fueling issue is, when your governor is what dictates rpm. (I am also assuming your set bellow max engine rpm in a fixed rpm application like this) especially since this carb is rated up to 50cc engines. Baring a factory screw up, I'd like a bit more information to better understand what has led to the determination of needed more fuel.
 
I don't know about heli setup but 3 1/2 turns on the high needle is double on a normal truck tune, and with that it would never turn a good high rpm. Just my 2 cents.
 
1820 rpm on the head the engine is running at 12,503rpm. At 2000 headspeed it would be running at 13,740. On a heli I can tell you from experience a 200rpm increase does change tune a bit if you want peak power. I am tuning by ear and power delivery as well as checking the plug. It is not lean now but will be if I increase rpm or the air temp lowers etc. I am putting new gaskets on the engine between the carb/insulator/engine next week and will test again. If nothing changes then I am going to try enlarging the highspeed channel if possible as well as trying a 990 carb as I have been told by other heli guys that that carb is bulletproof and works well. I will update with my findings when completed.
Gordo... said:
I don't know about heli setup but 3 1/2 turns on the high needle is double on a normal truck tune, and with that it would never turn a good high rpm. Just my 2 cents.
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I am not trying to gain rpm by tuning it. I am trying to get more fuel so I can safely raise my rpm
KevTrem said:
In a heli wouldn't it be almost free revving??

I'm sure I've been told or read somewhere that more than 2 turns out means you have issues.
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No because we use what is called a governor. It controls the throttle electronically through the servo to maintain a steady rpm that you set.
 
I just think at 3 1/2 turns on the high needle would be like me when I'm drunk, slurring and falling on my face.🤪🤪
This is 30 5 rcmk no load max rpm 1 5/8 high needle and 1 1/4 low.
 

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