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Carb Advice

Old 06-22-2016, 09:42 AM
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Lifer
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Default Carb Advice

A friend asked me to get his Zenoah 23 running for him. After a little coaxing, It is running but the high-speed needle has no effect. Low-speed needle gets the acceleration fine but the high-speed needle can be opened 2 to 5 turns with no change.

Any suggestions for correcting this?
Old 06-22-2016, 12:33 PM
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ahicks
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You've had it apart and cleaned it?

Sounds like a restriction, but it could be an air leak, and it could be anywhere from the tank clunk to the passage leading to the HS screw. I'd just go through the whole thing, and keep my fingers crossed that I find it on the first pass.
Old 06-22-2016, 01:00 PM
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Lifer
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I have never touched it. The engine is NIB, but who knows how old it is. The only clue I have is that the low-speed needle functions correctly.
Old 06-22-2016, 10:57 PM
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Most carbs are set with both needles at 2 - 21/4 from close position.
The LSN controls the engine RPM from idle to around 2/3-3/4 of the RPM range, the HSN controls the top 1/4.
You always start with the LSN and when the engine is tuned you can start leaning the HSN slowly.
OS published instructions for their Walbro heli engine: http://www.os-engines.co.jp/english/2013/130316e/
If you follow these instructions you should come right.
Old 06-23-2016, 06:43 PM
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Meschmidt
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Sounds like you have too much prop on it. 15x10 or 16x8 is the must you want to run on it. 15x8 for break in.
Old 06-24-2016, 12:53 AM
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Lifer
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It has a 16x6 on it. I'm going to see if I can borrow a high-speed needle from another engine and try that.
Old 06-24-2016, 04:14 AM
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Originally Posted by Lifer View Post
It has a 16x6 on it. I'm going to see if I can borrow a high-speed needle from another engine and try that.
If the HS needle had ever been tightened too much, it could have deformed the needle seat, opening up the orifice. A new needle would not help in this case. A deformed (bigger) seat would make tuning difficult, if not impossible. However, if the needle itself was deformed, causing a step on the needle taper, then a new needle could solve the issue. Good luck
Old 06-24-2016, 09:10 AM
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Tried the new needle. No change. My friend is going to order a carb kit and
I'll report after that is installed.

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