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Old Oct 27, 2012, 11:06 AM
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kerwin50's Avatar
winston mo
Joined Oct 2006
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I use a combo of the pinch test and pointing the nose up to check my hs needle. I quickly advance the throttle to check my ls needle. if it hesitates alot it's too rich. if it dies it's either got poor draw or too lean.
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Old Nov 04, 2012, 10:01 PM
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United States, MI, Bloomingdale
Joined Mar 2010
143 Posts
Heres just an update on my Alpha 40, before this weekend I haven't been able to fly much at all. I did get one flight in and the Alpha seemed to fly ok.

But this weekend I ran through 7 tanks and the engine is running worse than before when it was lean. Every now and then it'll run ok for a minute but then it will start running worse. The engine runs inconsistantly and will die after half throttle when its running bad no matter what my needles are set at. It seems like it isn't getting enough fuel even when the HSN is 4 turns out.
I've tried everything I can think of, I started out at 4 turns out with the HSN and worked my way to 1 3/4 turn from out. And did the same thing with the LSN, started really rich at the same time.

I've already replaced the fuel line and tried a new glow plug but the fix I don't think is going to be that simple. I think its an air leak some where else.

I talked to my father who is pretty knowledgeable about 2 stroke gas engines and we came to conclusion that it has to be an air leak somewhere or there is debris in the carb. It doesn't run consistantly, it acts like its not getting enough fuel and won't hold a tune.

Tomorrow I'm going to start at the fuel tank, then the HSN valve and work my way to the carb to check for leaks and clean it.


Also one other question, does the exhaust line that goes from the tank to the muffler pressurize the tank or is it just a breather tube? Thanks.
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Old Nov 04, 2012, 10:03 PM
use the 4s luke, use the 4s...
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Australia, QLD, Booyal
Joined Sep 2012
837 Posts
Did you replace the line in the tank?
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Old Nov 04, 2012, 10:07 PM
Garfield is my Pilot
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Joined May 2011
195 Posts
I had a loose throttle barrel in an engine and it ran just like you described.
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Old Nov 04, 2012, 10:09 PM
use the 4s luke, use the 4s...
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Australia, QLD, Booyal
Joined Sep 2012
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And the line has to connect to the muffler as it provides a head of pressure
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Old Nov 04, 2012, 10:17 PM
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United States, MI, Bloomingdale
Joined Mar 2010
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I didn't replace the line in the tank just on the outside, I'm thinking I should have? I'll do that before I tear apart the carb.

Also the blue collars aren't needed right? I ended up taking them off cause they got in the way even after I bent the tabs so I could actually move the needles.

Acdii how do you check if you have a loose throttle barrel?
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Old Nov 04, 2012, 10:25 PM
use the 4s luke, use the 4s...
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Australia, QLD, Booyal
Joined Sep 2012
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Wobble it. If it is loose it will have a fair bit of play in it. (Side to side and up and down. Not twisting type)
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Old Nov 04, 2012, 10:49 PM
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United States, MI, Bloomingdale
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Thanks scrub monkey, that may be my problem. I don't have it sitting infront of me but the barrel did seem to have some play in it, if I remember right.

I do remember the carb would sometimes not be a smooth twist to it, it would kind of twist and have some play side to side. I'll investigate it tomorrow.
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Old Nov 04, 2012, 10:53 PM
use the 4s luke, use the 4s...
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Australia, QLD, Booyal
Joined Sep 2012
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In and out play isn't too bad as if I am not mistaken there is usually a small light spring to keep the barrel too the out side. I'd starte by checking the fuel tank. I can almost guarantee that there will be pin holes in the pick up line
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Old Nov 04, 2012, 10:56 PM
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United States, MI, Bloomingdale
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Thanks again scrub monkey, I'll check that too tomorrow. I'm hoping thats the problem, I'll really hate to think about tearing the carb apart.
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Old Nov 04, 2012, 10:59 PM
use the 4s luke, use the 4s...
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Australia, QLD, Booyal
Joined Sep 2012
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The carbs are simple. I'll take a pic of an exploded view when I get home in about a couple of hours. They are dead easy and very simple in design
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Old Nov 05, 2012, 06:28 AM
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Joined Feb 2010
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there are normally two lines in the tank. the muffler pressure goes to the tank tube that is bent upwards towards the top of the tank. the carb line goes to a tube inside the tank that has the metal clunk pickup. make sure that line clears the rear of the tank by 1/4" so that it can freely flip around in the tank.

if there is a third line that would be just for filling/defuelling. i usually make that clunk considerably shorter than the carb clunk so they don't interfere.

make sure all of the engine bolts are snug.
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