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Old 09-02-2012, 06:08 PM
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Originally Posted by Theflyinglineman View Post
I assume this is on an engine that is broken in . I am talking about the part to set high end to max rpm. Just trying to learn.
I do this with any engine, but I disagree with the backing down the throttle and repeated leaning along with how he sets max. After you set the high I lean the low until it sags then richen until it doesn't, for setting the high I richen it until it starts to fall off, then stop and go back a tad, that way you are on the rich side of max, much better than being on the lean side of max.
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Old 09-06-2012, 09:59 AM
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Mintor 38 question. Its new and run through about 1 gallon so far. Motor starts and runs fairly well but I can not get this little engine to transition to WOT at all. Beyond 1/4 throttle it slows then to about 1/3 throttle it will stop. The walbro settings are 1.75 on L and H as the factory recommends and it just seems the motor is starving for fuel. I richen up the low and the motor can make it to almost 1/2 throttle before it dies but inevitably it will. I richen both needles to 2 turns out and its basically the same result. I removed the fuel lines and tank by replacing with a straight fuel line directly into another fuel tank 9 inches away and a new filter in an attempt to eliminate any fuel line restrictions. My dad runs the same motor and he has absolutely no problem with it at the factory 1.75 on both needles. Im using 91 pump gas with Sthil ultra full synthetic at about 40:1 and a 20X8 Master Airscrew prop. I cleaned the carb screen though it looked clean anyway. This motor will not transition to WOT despite my efforts. Any thoughts or ideas are greatly appreciated.
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Old 09-07-2012, 02:27 AM
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Originally Posted by dephcon5 View Post
Mintor 38 question. Its new and run through about 1 gallon so far. Motor starts and runs fairly well but I can not get this little engine to transition to WOT at all. Beyond 1/4 throttle it slows then to about 1/3 throttle it will stop. The walbro settings are 1.75 on L and H as the factory recommends and it just seems the motor is starving for fuel. I richen up the low and the motor can make it to almost 1/2 throttle before it dies but inevitably it will. I richen both needles to 2 turns out and its basically the same result. I removed the fuel lines and tank by replacing with a straight fuel line directly into another fuel tank 9 inches away and a new filter in an attempt to eliminate any fuel line restrictions. My dad runs the same motor and he has absolutely no problem with it at the factory 1.75 on both needles. Im using 91 pump gas with Sthil ultra full synthetic at about 40:1 and a 20X8 Master Airscrew prop. I cleaned the carb screen though it looked clean anyway. This motor will not transition to WOT despite my efforts. Any thoughts or ideas are greatly appreciated.
High end probably too rich. Open throttle until the rpm sags and then close high end until it picks up again.
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Old 09-07-2012, 05:09 PM
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I did a few things and so far the result is the same. I can not get this motor to transition to WOT at all. I started with the L at factory 1.75 turns out. I set the H at 1 turn out. Factory suggests 1.75 on both so the H at 1 should be far to the lean side. I fire up the engine, let it warm up and advance the throttle. At about 1/3 up it stalled and so I open the H needle in 5 minute increments until I get to about 3 full turns out. At 3 turns it should be way too rich but this motor does the same thing at about 1/3 to 1/2 throttle, it quits. From far too lean to far too rich this motor will not go to WOT. I will take it off the airframe and put it back on the test stand and troubleshoot from there. It seems the high circuit just is not engaging for some reason. It quits rather quickly so I can only conclude it is the high circuit not operating. Im open to any ideas if anyone has any.
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Old 09-07-2012, 06:13 PM
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Quote:
Originally Posted by dephcon5 View Post
I did a few things and so far the result is the same. I can not get this motor to transition to WOT at all. I started with the L at factory 1.75 turns out. I set the H at 1 turn out. Factory suggests 1.75 on both so the H at 1 should be far to the lean side. I fire up the engine, let it warm up and advance the throttle. At about 1/3 up it stalled and so I open the H needle in 5 minute increments until I get to about 3 full turns out. At 3 turns it should be way too rich but this motor does the same thing at about 1/3 to 1/2 throttle, it quits. From far too lean to far too rich this motor will not go to WOT. I will take it off the airframe and put it back on the test stand and troubleshoot from there. It seems the high circuit just is not engaging for some reason. It quits rather quickly so I can only conclude it is the high circuit not operating. Im open to any ideas if anyone has any.
Are you sure the carb is clean, and all parts installed as they should be? Possibly sounds like the metering diaphram is in upside down, or .........

You do have a vent line on your tank?
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Old 09-07-2012, 07:28 PM
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Quote:
Originally Posted by dephcon5 View Post
I did a few things and so far the result is the same. I can not get this motor to transition to WOT at all. I started with the L at factory 1.75 turns out. I set the H at 1 turn out. Factory suggests 1.75 on both so the H at 1 should be far to the lean side. I fire up the engine, let it warm up and advance the throttle. At about 1/3 up it stalled and so I open the H needle in 5 minute increments until I get to about 3 full turns out. At 3 turns it should be way too rich but this motor does the same thing at about 1/3 to 1/2 throttle, it quits. From far too lean to far too rich this motor will not go to WOT. I will take it off the airframe and put it back on the test stand and troubleshoot from there. It seems the high circuit just is not engaging for some reason. It quits rather quickly so I can only conclude it is the high circuit not operating. Im open to any ideas if anyone has any.
I answered this question for you in another thread. Now that you've verified it stops abruptly when going from low to high you confirmed the diagnosis. The high speed circuit is blocked and needs to be cleaned out.

This is not an infrequent problem, nor unique to Mintor The solution is quite simple and won't require more than an hour of your time. Disassemble the carb completely and follow the directions I provided in your other thread. The basic clean and assembly process.
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Old 09-07-2012, 07:40 PM
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I took the time to study the exploded view of this model Walbro so I could get an idea of what I am looking at. With that, I tore down the carb and it looked clean but I went through and sprayed carb cleaner through the ports and I can see its all flowing as it should. Its late now but I will have time tomorrow to mount it and test again. I am not certain this will change anything but I will go back and double check the plug, gap, fuel lines, clunk and anything I can eliminate as a variable. We'll see what happens. This has me really baffled but it seems to be narrowed down to the high circuit not delivering for what ever reason.
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Old 09-07-2012, 08:49 PM
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It is definitely in the the high speed circiut of the carburetor. The engine is still under warranty, contact the US distributor responsible for executing warranty claims, get a new carburetor, go on with your life and fly.
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Old 09-08-2012, 09:45 AM
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Old 09-08-2012, 10:40 AM
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This is an 8.54Mb file. Maybe more people will have a better understanding of what they are doing if they read it and understand how the carb works.

Maybe it should be put in the O.P.
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Old 09-08-2012, 11:00 AM
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Originally Posted by wecoyote View Post
This is an 8.54Mb file. Maybe more people will have a better understanding of what they are doing if they read it and understand how the carb works.

Maybe it should be put in the O.P.
Thanks for the pdf.
Again, feedback is always appreciated.
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Old 09-08-2012, 12:51 PM
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Thanks for posting the manual. Once one looks through it they will understand why I suggested cleaning the high speed circuit again. When it was mentioned the owner had looked into the circuit and saw that it was clear I recognized he didn't understand the carb. You can't "look through" the high speed circuit of a butterfly carb.

The manual depicts two types of carbs. The first is a rotating barrel (WY) carb like those found on yard tools. The second carb type is what most of us use on our planes. WB, WT, WG, SD, etc.
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Old 09-08-2012, 03:00 PM
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On a long shot I made a short trip to a Stihl lawnmower shop dealer guru and he gave me a few pointers. I broght my motor with me and he looked up the Walbro number and didnt find it in his literature so he called some friend of his. He then suggested I change the metering spring that feeds the high speed circuit and handed me 2 replacements. He said if the spring is too strong it may prevent the H circuit from getting any fuel. He said it was possible the spring was the wrong one when assembled or maybe with a new motor its not making enough vacuum until the ring is fully broken in. One spring was the correct weight for the carb and the second spring he gave me was one stage weaker. When I got home, I replaced the spring inside the carb with the weaker replacement and gave it a test run. It may be related to the Texas summer heat and thin air but I suspect that is debatable. I do miss NY sometimes... I digress. Anyway, the spring worked. Not only does the motor go to WOT but it really screams! I should be in the air tomorrow
Thanks to all of you in this and other forums. The info and ideas are always appreciated.
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Old 09-08-2012, 03:14 PM
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Wow.........good call on trying the local small engine shop.

Just another thing to add to the check list if the engine is having some running issues. I know very little about 2 cycle engines and their carburetors. They may be simple when compared to other engines but a bit overwhelming to a noob...........

Thank goodness for sites like this where there is a lot of experience/knowledge available to help when an issue comes up.
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Old 09-08-2012, 03:56 PM
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Originally Posted by Capt. Roll View Post
Wow.........good call on trying the local small engine shop.

Just another thing to add to the check list if the engine is having some running issues. I know very little about 2 cycle engines and their carburetors. They may be simple when compared to other engines but a bit overwhelming to a noob...........

Thank goodness for sites like this where there is a lot of experience/knowledge available to help when an issue comes up.
I agree on all points.
I didnt have that kind of resource near by until I moved to Texas.

I also need to note that with that spring change: if it is too weak then it will not close off the high speed circuit fast enough, the engine will flood and stall if you come off WOT too quickly. Just the opposite is if the spring is too strong, the motor will starve for fuel as you advance to WOT and the high circuit will not get any fuel.
Thats how it was explained to me, hope this info is correct but it makes sense at least to me. I remember the old Carter 625 carb I had on an old Ford 302 worked in a similar way with the rods that would rise out of the primary jets with vacuum and a spring controlling when it moved. Holly carbs use a power valve on the primary metering block. Going back 20 years but if my memory serves me ringt, the theory behind these two and the Walbro H circuit is about the same (give or take).
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